0.3.02-alpha: notes cover better calls, the Home row, and call audio over Bluetooth

Small labelled buttons pinned at the bottom of Home, so cards above can't push them out of sight.
Help and tools leaves Settings, Connection help (the same page as Help) goes, What's new moves to
the top of Settings, the intro replay goes, and the debug build's test message gets its own
section there.

.github/release-notes.md

@@ -1,15 +1,27 @@
-Gearslip 0.3.01 connects wirelessly on more phones and dongles.
+Gearslip 0.3.02 connects wirelessly by itself, and phone calls work much better.
 
-## Fixed
-- Wireless works with dongles that send their Wi-Fi details before their address.
-- A VPN no longer stops a wireless drive without a word. Gearslip tries the phone's ordinary route around it, and if the VPN still blocks the car, Gearslip says so. To fix it for good, exclude Gearslip in your VPN app.
-- When Android won't ask for the Nearby devices permission, a button opens Gearslip's settings, where you can turn it on.
+## New
+- Wireless connects by itself. After your first wireless drive, Android asks once whether Gearslip may watch for that car. From then on, Gearslip connects whenever the car's Bluetooth does. A USB cable still wins.
+- Phone calls work much better. Calls you place from the car's dialer go through, and you can end or mute a call from the nav bar, which shows who you're talking to and for how long.
+- The browser goes full screen, for the whole page or a video in it.
+- The nav bar can hide while you navigate, or until you tap the screen.
+- Directions sit in short bars, so map apps keep their maps clear of them.
+- Share a log from an earlier launch, not just the current one.
+- In the car preview, you type with the phone's keyboard.
 
 ## Changed
-- An app that someone else has re-signed, such as a modified Waze, no longer shows the red X when it accepts Gearslip.
-- Support Gearslip through Liberapay, Buy Me a Coffee, or Monero, in Settings.
-- Gearslip now belongs to Twink Software LLC, and its code lives at github.com/twinksoftware/gearslip. Old links still work.
-- The README lists Gearslip's signing certificate, so you can check your copy with AppVerifier.
+- Help, Preview, and Logs sit in a row at the bottom of the phone's home screen.
+- What's new, at the top of Settings, opens the release notes here on GitHub.
+
+## Fixed
+- Before each spoken turn, Gearslip asks the car for its speakers, as Android Auto does. Some head units rebooted without this.
+- An app that won't run in Gearslip, such as Yandex Maps or 2GIS, now says so after 10 seconds instead of showing "Starting" forever.
+- Head units that take only AAC music get one start message, not two. A 2014 aftermarket unit dropped the connection over the second.
+- With music on Bluetooth, the car keeps its Bluetooth source.
+- Head units offering Android Auto 4.x and 6.x get a version they accept.
+- Homemade head units without a certificate keep working, and the wheel buttons and knob work as they do in the main build.
+- A car that reports the wrong screen size gets the right one.
+- iscle fixed how Gearslip frames, secures, and negotiates the connection, and how it checks what the car sends.
 
 ## Known issues
-- Phone calls are unstable right now and may drop or fail to connect.
+- Call audio plays through the car's Bluetooth phone connection, as it does with Android Auto. If a call plays on the phone instead, open the car in the phone's Bluetooth settings and turn on Phone calls.

gearslip/build.gradle.kts

@@ -38,9 +38,9 @@ android {
         applicationId = "app.seb3thehacker.gearslip"
         minSdk = 31
         targetSdk = 37
-        versionCode = 10
+        versionCode = 11
         // -PgearslipVersionName=0.1.99-test makes a build that thinks it's older, to try the updater.
-        versionName = project.findProperty("gearslipVersionName")?.toString() ?: "0.3.01-alpha"
+        versionName = project.findProperty("gearslipVersionName")?.toString() ?: "0.3.02-alpha"
         manifestPlaceholders["appLabel"] = "Gearslip"
         // Where opted-in phones send their daily usage note: the stats-worker/ Worker's address,
         // set as gearslipStatsUrl in gradle.properties. Left empty, nothing is ever sent.
@@ -74,8 +74,9 @@ android {
             applicationIdSuffix = ".dev"
             signingConfigs.findByName("release")?.let { signingConfig = it }
             manifestPlaceholders["appLabel"] = "Gearslip Debug"
-            // -Pr8 shrinks a debug build like a release one, to test R8 in the debug install.
-            if (project.hasProperty("r8")) {
+            // Shrunk with R8 like a release, so a debug install behaves like what ships (a keep
+            // rule missing for release shows up here first). -PnoR8 skips it for a quicker build.
+            if (!project.hasProperty("noR8")) {
                 isMinifyEnabled = true
                 isShrinkResources = true
                 proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")

gearslip/src/main/AndroidManifest.xml

@@ -25,6 +25,9 @@
         hands over its Wi-Fi details; Gearslip then joins that network to reach the car.
     -->
     <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
+    <!-- Wireless auto-connect: Android tells Gearslip when a car it manages connects. -->
+    <uses-permission android:name="android.permission.REQUEST_OBSERVE_COMPANION_DEVICE_PRESENCE" />
+    <uses-feature android:name="android.software.companion_device_setup" android:required="false" />
     <uses-permission android:name="android.permission.BLUETOOTH" android:maxSdkVersion="30" />
     <uses-permission
         android:name="android.permission.NEARBY_WIFI_DEVICES"
@@ -244,5 +247,15 @@
                 <action android:name="android.telecom.CallScreeningService" />
             </intent-filter>
         </service>
+
+        <!-- Told when a car approved for wireless auto-connect comes up over Bluetooth. -->
+        <service
+            android:name=".wireless.CarPresenceService"
+            android:exported="true"
+            android:permission="android.permission.BIND_COMPANION_DEVICE_SERVICE">
+            <intent-filter>
+                <action android:name="android.companion.CompanionDeviceService" />
+            </intent-filter>
+        </service>
     </application>
 </manifest>

gearslip/src/main/java/app/seb3thehacker/gearslip/FrameStretcher.kt

@@ -0,0 +1,190 @@
+package app.seb3thehacker.gearslip
+
+import android.graphics.SurfaceTexture
+import android.opengl.EGL14
+import android.opengl.EGLConfig
+import android.opengl.EGLContext
+import android.opengl.EGLDisplay
+import android.opengl.EGLExt
+import android.opengl.EGLSurface
+import android.opengl.GLES11Ext
+import android.opengl.GLES20
+import android.os.Handler
+import android.os.HandlerThread
+import android.view.Surface
+import java.nio.ByteBuffer
+import java.nio.ByteOrder
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+
+/**
+ * Stretches a [width] x [height] picture over the whole of an [outWidth] x [outHeight] encoder
+ * frame.
+ *
+ * For a head unit that squashes the frame onto a screen of another shape: Gearslip draws for the
+ * screen's real shape into [input], this stretches it the other way, and the car's squash brings
+ * it back. It works on the composited picture, so a map app's own surface is stretched with
+ * everything else - scaling Gearslip's UI alone would leave the map squashed.
+ */
+class FrameStretcher(
+    private val output: Surface,
+    val width: Int,
+    val height: Int,
+    private val outWidth: Int,
+    private val outHeight: Int,
+) {
+
+    private val thread = HandlerThread("gearslip-stretch").apply { start() }
+    private val handler = Handler(thread.looper)
+
+    private var display: EGLDisplay = EGL14.EGL_NO_DISPLAY
+    private var context: EGLContext = EGL14.EGL_NO_CONTEXT
+    private var eglSurface: EGLSurface = EGL14.EGL_NO_SURFACE
+    private var program = 0
+    private var texture: SurfaceTexture? = null
+    private val transform = FloatArray(16)
+
+    /** Where to draw. Valid once [start] returns true. */
+    lateinit var input: Surface
+        private set
+
+    /** Sets up on its own thread and waits for it; false if the GPU wouldn't play along. */
+    fun start(): Boolean {
+        val done = CountDownLatch(1)
+        var ok = false
+        handler.post {
+            ok = runCatching { setUp() }
+                .onFailure { GearslipLog.e("stretch: could not set up", it) }
+                .isSuccess
+            done.countDown()
+        }
+        done.await(2, TimeUnit.SECONDS)
+        if (!ok) release()
+        return ok
+    }
+
+    fun release() {
+        handler.post {
+            runCatching { if (::input.isInitialized) input.release() }
+            runCatching { texture?.release() }
+            texture = null
+            if (display != EGL14.EGL_NO_DISPLAY) {
+                EGL14.eglMakeCurrent(display, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_SURFACE, EGL14.EGL_NO_CONTEXT)
+                if (eglSurface != EGL14.EGL_NO_SURFACE) EGL14.eglDestroySurface(display, eglSurface)
+                if (context != EGL14.EGL_NO_CONTEXT) EGL14.eglDestroyContext(display, context)
+                EGL14.eglTerminate(display)
+            }
+            display = EGL14.EGL_NO_DISPLAY
+            thread.quitSafely()
+        }
+    }
+
+    private fun setUp() {
+        display = EGL14.eglGetDisplay(EGL14.EGL_DEFAULT_DISPLAY)
+        val version = IntArray(2)
+        check(EGL14.eglInitialize(display, version, 0, version, 1)) { "eglInitialize failed" }
+        val configs = arrayOfNulls<EGLConfig>(1)
+        val count = IntArray(1)
+        val attributes = intArrayOf(
+            EGL14.EGL_RED_SIZE, 8, EGL14.EGL_GREEN_SIZE, 8, EGL14.EGL_BLUE_SIZE, 8,
+            EGL14.EGL_RENDERABLE_TYPE, EGL14.EGL_OPENGL_ES2_BIT,
+            EGL_RECORDABLE_ANDROID, 1,
+            EGL14.EGL_NONE,
+        )
+        check(EGL14.eglChooseConfig(display, attributes, 0, configs, 0, 1, count, 0) && count[0] > 0) {
+            "no EGL config"
+        }
+        context = EGL14.eglCreateContext(
+            display, configs[0], EGL14.EGL_NO_CONTEXT,
+            intArrayOf(EGL14.EGL_CONTEXT_CLIENT_VERSION, 2, EGL14.EGL_NONE), 0,
+        )
+        eglSurface = EGL14.eglCreateWindowSurface(display, configs[0], output, intArrayOf(EGL14.EGL_NONE), 0)
+        check(EGL14.eglMakeCurrent(display, eglSurface, eglSurface, context)) { "eglMakeCurrent failed" }
+
+        program = link(VERTEX, FRAGMENT)
+        val ids = IntArray(1)
+        GLES20.glGenTextures(1, ids, 0)
+        GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, ids[0])
+        GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR)
+        GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR)
+        GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_CLAMP_TO_EDGE)
+        GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_CLAMP_TO_EDGE)
+
+        texture = SurfaceTexture(ids[0]).apply {
+            setDefaultBufferSize(width, height)
+            setOnFrameAvailableListener({ draw() }, handler)
+        }
+        input = Surface(texture)
+        GearslipLog.i("stretch: drawing ${width}x$height, stretched to fill ${outWidth}x$outHeight")
+    }
+
+    private fun draw() {
+        val tex = texture ?: return
+        runCatching {
+            tex.updateTexImage()
+            tex.getTransformMatrix(transform)
+            GLES20.glViewport(0, 0, outWidth, outHeight)
+            GLES20.glUseProgram(program)
+            val position = GLES20.glGetAttribLocation(program, "aPosition")
+            val coord = GLES20.glGetAttribLocation(program, "aCoord")
+            GLES20.glEnableVertexAttribArray(position)
+            GLES20.glVertexAttribPointer(position, 2, GLES20.GL_FLOAT, false, 0, QUAD)
+            GLES20.glEnableVertexAttribArray(coord)
+            GLES20.glVertexAttribPointer(coord, 2, GLES20.GL_FLOAT, false, 0, COORDS)
+            GLES20.glUniformMatrix4fv(GLES20.glGetUniformLocation(program, "uTransform"), 1, false, transform, 0)
+            GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4)
+            EGLExt.eglPresentationTimeANDROID(display, eglSurface, tex.timestamp)
+            EGL14.eglSwapBuffers(display, eglSurface)
+        }.onFailure { GearslipLog.e("stretch: draw failed", it) }
+    }
+
+    private fun link(vertex: String, fragment: String): Int {
+        fun compile(type: Int, source: String): Int = GLES20.glCreateShader(type).also {
+            GLES20.glShaderSource(it, source)
+            GLES20.glCompileShader(it)
+            val status = IntArray(1)
+            GLES20.glGetShaderiv(it, GLES20.GL_COMPILE_STATUS, status, 0)
+            check(status[0] != 0) { "shader: ${GLES20.glGetShaderInfoLog(it)}" }
+        }
+        return GLES20.glCreateProgram().also {
+            GLES20.glAttachShader(it, compile(GLES20.GL_VERTEX_SHADER, vertex))
+            GLES20.glAttachShader(it, compile(GLES20.GL_FRAGMENT_SHADER, fragment))
+            GLES20.glLinkProgram(it)
+            val status = IntArray(1)
+            GLES20.glGetProgramiv(it, GLES20.GL_LINK_STATUS, status, 0)
+            check(status[0] != 0) { "program: ${GLES20.glGetProgramInfoLog(it)}" }
+        }
+    }
+
+    private companion object {
+        /** EGL_RECORDABLE_ANDROID: the config must be able to feed a video encoder. */
+        const val EGL_RECORDABLE_ANDROID = 0x3142
+
+        val QUAD = floats(-1f, -1f, 1f, -1f, -1f, 1f, 1f, 1f)
+        val COORDS = floats(0f, 0f, 1f, 0f, 0f, 1f, 1f, 1f)
+
+        fun floats(vararg values: Float) = ByteBuffer.allocateDirect(values.size * 4)
+            .order(ByteOrder.nativeOrder()).asFloatBuffer().apply { put(values); position(0) }
+
+        const val VERTEX = """
+            attribute vec4 aPosition;
+            attribute vec4 aCoord;
+            uniform mat4 uTransform;
+            varying vec2 vCoord;
+            void main() {
+                gl_Position = aPosition;
+                vCoord = (uTransform * aCoord).xy;
+            }
+        """
+
+        const val FRAGMENT = """
+            #extension GL_OES_EGL_image_external : require
+            precision mediump float;
+            varying vec2 vCoord;
+            uniform samplerExternalOES sTexture;
+            void main() {
+                gl_FragColor = texture2D(sTexture, vCoord);
+            }
+        """
+    }
+}

gearslip/src/main/java/app/seb3thehacker/gearslip/Framing.kt

@@ -1,20 +1,10 @@
 package app.seb3thehacker.gearslip
 
 import java.io.ByteArrayOutputStream
+import java.io.IOException
+import java.io.OutputStream
 
-/**
- * Android Auto frame layout, transcribed from aasdk.
- *
- * FrameHeader::getData (src/Messenger/FrameHeader.cpp:47-55),
- * FrameSize::getData (src/Messenger/FrameSize.cpp:49-62) and
- * MessageOutStream::compoundFrame (src/Messenger/MessageOutStream.cpp:100-120):
- *
- *   byte 0     channel id
- *   byte 1     frameType | encryption | messageType
- *   bytes 2-3  uint16 BE  payload length of THIS frame
- *   bytes 4-7  uint32 BE  total message length - present ONLY when frameType == FIRST
- *   payload    uint16 BE message id, then the body
- */
+/** Android Auto framing with plaintext fragmentation before per-frame encryption. */
 object Frames {
 
     const val CHANNEL_CONTROL = 0
@@ -36,8 +26,11 @@ object Frames {
     const val MESSAGE_SPECIFIC = 0
     const val MESSAGE_CONTROL = 1 shl 2
 
-    /** aasdk splits at this size (MessageOutStream.hpp:62). Nothing the spike sends is close. */
-    const val MAX_FRAME_PAYLOAD = 0x4000
+    // Android Auto's default fragment budget includes the framing header. TLS adds overhead.
+    private const val FRAGMENT_SIZE = 0x3f00
+    private const val HEADER_SIZE = 4
+    private const val FIRST_HEADER_SIZE = 8
+    const val MAX_FRAME_PAYLOAD = FRAGMENT_SIZE - HEADER_SIZE
 
     class Frame(
         val channel: Int,
@@ -45,6 +38,7 @@ object Frames {
         val encrypted: Boolean,
         val messageType: Int,
         val payload: ByteArray,
+        val totalSize: Int? = null,
     )
 
     /**
@@ -60,6 +54,11 @@ object Frames {
         frameType: Int = TYPE_BULK,
         totalSize: Int? = null,
     ): ByteArray {
+        require(channel in 0..255 && payload.size <= 0xffff)
+        require(frameType in TYPE_MIDDLE..TYPE_BULK)
+        require(messageType == MESSAGE_SPECIFIC || messageType == MESSAGE_CONTROL)
+        require((frameType == TYPE_FIRST) == (totalSize != null))
+        require(totalSize == null || totalSize in 2..MAX_MESSAGE_SIZE)
         val flags = frameType or messageType or (if (encrypted) ENCRYPTED else 0)
         val header = byteArrayOf(
             channel.toByte(),
@@ -67,7 +66,7 @@ object Frames {
             ((payload.size shr 8) and 0xFF).toByte(),
             (payload.size and 0xFF).toByte(),
         )
-        if (frameType != TYPE_FIRST || totalSize == null) return header + payload
+        if (totalSize == null) return header + payload
         val extended = byteArrayOf(
             ((totalSize shr 24) and 0xFF).toByte(),
             ((totalSize shr 16) and 0xFF).toByte(),
@@ -77,6 +76,43 @@ object Frames {
         return header + extended + payload
     }
 
+    /** Splits plaintext before encryption; FIRST carries the complete plaintext length. */
+    fun writeMessage(
+        output: OutputStream,
+        channel: Int,
+        encrypted: Boolean,
+        messageType: Int,
+        message: ByteArray,
+        encrypt: (ByteArray) -> ByteArray,
+    ): Int {
+        require(message.size in 2..MAX_MESSAGE_SIZE)
+        val fragmented = message.size > FRAGMENT_SIZE - HEADER_SIZE
+        require(messageType != MESSAGE_CONTROL || !fragmented) { "Channel control messages cannot be fragmented" }
+        var offset = 0
+        var frames = 0
+        while (offset < message.size) {
+            val first = fragmented && offset == 0
+            val headerSize = if (first) FIRST_HEADER_SIZE else HEADER_SIZE
+            val end = minOf(offset + FRAGMENT_SIZE - headerSize, message.size)
+            val type = when {
+                !fragmented -> TYPE_BULK
+                first -> TYPE_FIRST
+                end == message.size -> TYPE_LAST
+                else -> TYPE_MIDDLE
+            }
+            val chunk = message.copyOfRange(offset, end)
+            output.write(build(channel, encrypted, if (encrypted) encrypt(chunk) else chunk,
+                messageType, type, if (type == TYPE_FIRST) message.size else null))
+            offset = end
+            frames++
+        }
+        return frames
+    }
+
+    // Local resource limits, not protocol constants. No supported media packet needs more.
+    private const val MAX_MESSAGE_SIZE = 16 * 1024 * 1024
+    private const val MAX_BUFFERED_SIZE = 32 * 1024 * 1024
+
     /**
      * Pulls whole frames out of an accumulating buffer.
      *
@@ -87,6 +123,8 @@ object Frames {
         private var pending = ByteArray(0)
 
         fun append(data: ByteArray, length: Int) {
+            require(length in 0..data.size)
+            if (length > MAX_BUFFERED_SIZE - pending.size) throw IOException("Frame buffer limit exceeded")
             val grown = ByteArray(pending.size + length)
             System.arraycopy(pending, 0, grown, 0, pending.size)
             System.arraycopy(data, 0, grown, pending.size, length)
@@ -106,30 +144,53 @@ object Frames {
             val total = headerLength + frameSize
             if (pending.size < total) return null
 
+            val messageSize = if (frameType == TYPE_FIRST) {
+                var size = 0L
+                for (i in 4..7) size = (size shl 8) or (pending[i].toLong() and 0xff)
+                if (size !in 2..MAX_MESSAGE_SIZE.toLong()) throw IOException("Invalid fragmented message length: $size")
+                size.toInt()
+            } else null
             val payload = pending.copyOfRange(headerLength, total)
             pending = pending.copyOfRange(total, pending.size)
             return Frame(
-                channel, frameType, (flags and ENCRYPTED) != 0, flags and MESSAGE_CONTROL, payload,
+                channel, frameType, (flags and ENCRYPTED) != 0, flags and MESSAGE_CONTROL, payload, messageSize,
             )
         }
     }
 
-    /** Rejoins FIRST/MIDDLE/LAST runs. Payloads arrive already decrypted. */
+    /** Rejoins messages on independent channels, validating their plaintext length and flags. */
     class Assembler {
-        private val partial = HashMap<Int, ByteArrayOutputStream>()
+        private class Partial(val first: Frame, val data: ByteArrayOutputStream = ByteArrayOutputStream())
+        private val partial = HashMap<Int, Partial>()
+        private var buffered = 0
 
-        fun offer(frame: Frame, payload: ByteArray): ByteArray? = when (frame.frameType) {
-            TYPE_BULK -> payload
-            TYPE_FIRST -> {
-                partial[frame.channel] = ByteArrayOutputStream().apply { write(payload) }
-                null
+        fun offer(frame: Frame, payload: ByteArray): ByteArray? {
+            if (frame.frameType == TYPE_BULK) {
+                if (partial.containsKey(frame.channel)) fail("Complete message interrupted fragments")
+                return payload
             }
-            TYPE_MIDDLE -> {
-                partial[frame.channel]?.write(payload)
-                null
-            }
-            TYPE_LAST -> partial.remove(frame.channel)?.apply { write(payload) }?.toByteArray()
-            else -> null
+            val message = if (frame.frameType == TYPE_FIRST) {
+                if (frame.totalSize == null || partial.containsKey(frame.channel)) fail("Invalid first fragment")
+                Partial(frame).also { partial[frame.channel] = it }
+            } else partial[frame.channel] ?: fail("Fragment without a first frame")
+            val first = message.first
+            if (first.encrypted != frame.encrypted || first.messageType != frame.messageType) fail("Fragment flags changed")
+            val expected = first.totalSize ?: fail("Missing total size")
+            if (expected !in 2..MAX_MESSAGE_SIZE || payload.size > expected - message.data.size()) fail("Fragment exceeds message length")
+            if (payload.size > MAX_BUFFERED_SIZE - buffered) fail("Fragment buffer limit exceeded")
+            message.data.write(payload)
+            buffered += payload.size
+            if (frame.frameType != TYPE_LAST) return null
+            if (message.data.size() != expected) fail("Truncated fragmented message")
+            partial.remove(frame.channel)
+            buffered -= message.data.size()
+            return message.data.toByteArray()
+        }
+
+        private fun fail(message: String): Nothing {
+            partial.clear()
+            buffered = 0
+            throw IOException(message)
         }
     }
 }

gearslip/src/main/java/app/seb3thehacker/gearslip/GearslipActivity.kt

@@ -117,6 +117,17 @@ class GearslipActivity : ComponentActivity(), Projection {
         }
     }
 
+    /** Android's one-time "Allow" for a car to connect by itself; see [WirelessAuto]. */
+    private var approvingCar: String? = null
+    private val carApproval = registerForActivityResult(
+        androidx.activity.result.contract.ActivityResultContracts.StartIntentSenderForResult(),
+    ) { result ->
+        val address = approvingCar ?: return@registerForActivityResult
+        approvingCar = null
+        if (result.resultCode == RESULT_OK) app.seb3thehacker.gearslip.wireless.WirelessAuto.approved(this, address)
+        else app.seb3thehacker.gearslip.wireless.WirelessAuto.declined(this, address)
+    }
+
     /** Setting Gearslip as the phone's caller ID and spam app - what lets it decline a ringing call. */
     private val callScreeningRole = registerForActivityResult(StartActivityForResult()) { result ->
         if (result.resultCode != RESULT_OK) GearslipLog.w("calls: call screening role declined")
@@ -138,6 +149,12 @@ class GearslipActivity : ComponentActivity(), Projection {
         app.seb3thehacker.gearslip.wireless.WirelessLink.onConnected = { socket ->
             runOnUiThread { startWireless(socket) }
         }
+        app.seb3thehacker.gearslip.wireless.WirelessAuto.showApproval = { chooser, address ->
+            runOnUiThread {
+                approvingCar = address
+                carApproval.launch(androidx.activity.result.IntentSenderRequest.Builder(chooser).build())
+            }
+        }
         CarSettings.init(this)
         AppSettings.applyGearslipEnabled(this)
         // A capture that died without tidying up would leave notifications exposed to every
@@ -216,6 +233,7 @@ class GearslipActivity : ComponentActivity(), Projection {
     override fun onDestroy() {
         super.onDestroy()
         app.seb3thehacker.gearslip.wireless.WirelessLink.onConnected = null
+        app.seb3thehacker.gearslip.wireless.WirelessAuto.showApproval = null
         runCatching { unregisterReceiver(detachReceiver) }
         PhoneMirror.onStartRequested = null
         PhoneMirror.onTokenReady = null
@@ -304,6 +322,10 @@ class GearslipActivity : ComponentActivity(), Projection {
     }
 
     private fun handleIntent(intent: Intent?) {
+        if (intent?.action == app.seb3thehacker.gearslip.wireless.WirelessAuto.ACTION_CAR_NEARBY) {
+            connectToNearbyCar(intent.getStringExtra(app.seb3thehacker.gearslip.wireless.WirelessAuto.EXTRA_ADDRESS))
+            return
+        }
         if (intent?.action != UsbManager.ACTION_USB_ACCESSORY_ATTACHED) return
         // Switched off in Settings: the system shouldn't route the car here at all, but if it
         // does, leave the accessory alone.
@@ -321,6 +343,39 @@ class GearslipActivity : ComponentActivity(), Projection {
         start(accessory)
     }
 
+    /** A known car came up over Bluetooth: connect wirelessly, unless USB or another try is already on it. */
+    private fun connectToNearbyCar(address: String?) {
+        if (address == null) return
+        if (!AppSettings.gearslipEnabled(this)) {
+            GearslipLog.i("auto-connect: Gearslip is switched off - not connecting")
+            return
+        }
+        if (descriptor != null) {
+            GearslipLog.i("auto-connect: the car is on USB already - staying on USB")
+            return
+        }
+        // Only a session that's still running counts. One the car ended (a ByeBye, a dropped
+        // network) leaves its runner behind, since only Gearslip ending a session clears it, and
+        // that used to make every later auto-connect quietly do nothing.
+        if (worker?.isAlive == true || app.seb3thehacker.gearslip.wireless.WirelessLink.busy) {
+            GearslipLog.i("auto-connect: a session is already running")
+            return
+        }
+        if (runner != null) closeAccessory(stopWireless = false)
+        if (checkSelfPermission(android.Manifest.permission.BLUETOOTH_CONNECT) != android.content.pm.PackageManager.PERMISSION_GRANTED) {
+            GearslipLog.w("auto-connect: needs the Nearby devices permission")
+            return
+        }
+        val adapter = getSystemService(android.bluetooth.BluetoothManager::class.java)?.adapter
+        val device = adapter?.let { runCatching { it.getRemoteDevice(address) }.getOrNull() }
+        if (device == null) {
+            GearslipLog.w("auto-connect: Bluetooth couldn't hand over the car")
+            return
+        }
+        GearslipLog.i("auto-connect: connecting")
+        app.seb3thehacker.gearslip.wireless.WirelessLink.start(this, device)
+    }
+
     private fun start(accessory: UsbAccessory) {
         // A fresh ATTACHED intent means the system wants a new session, whatever state the old
         // one is in - closing first guarantees openAccessory() below never fights a descriptor

gearslip/src/main/java/app/seb3thehacker/gearslip/GearslipLog.kt

@@ -52,6 +52,46 @@ object GearslipLog {
         file = File(dir, "gearslip-$name.log")
         i("log file: ${file?.absolutePath}")
         SessionReport.init(context)
+        // One file per launch adds up; the newest are the ones anyone asks for.
+        io.execute { logFiles(dir).drop(KEEP_FILES).forEach { it.delete() } }
+    }
+
+    private const val KEEP_FILES = 30
+
+    private fun logFiles(dir: File): List<File> =
+        dir.listFiles { f -> f.isFile && f.name.startsWith("gearslip-") && f.name.endsWith(".log") }
+            ?.sortedByDescending { it.name }.orEmpty()
+
+    /** A log from an earlier launch: when it started, and what a glance at it tells. */
+    class PastLog(val file: File, val started: Date?, val crashed: Boolean, val car: String?)
+
+    /**
+     * Earlier launches' logs, newest first. Each launch starts a fresh file, so after a crash the
+     * one that saw it is here rather than on the live screen.
+     */
+    fun pastLogs(context: Context): List<PastLog> {
+        val dir = context.getExternalFilesDir(null) ?: return emptyList()
+        val parse = SimpleDateFormat("yyyyMMdd-HHmmss", Locale.US)
+        return logFiles(dir).filter { it != file }.map { f ->
+            val text = runCatching { f.readText() }.getOrDefault("")
+            PastLog(
+                file = f,
+                started = runCatching { parse.parse(f.name.removePrefix("gearslip-").removeSuffix(".log")) }.getOrNull(),
+                crashed = "FATAL uncaught" in text,
+                car = Regex("""car="([^"]+)"""").findAll(text).lastOrNull()?.groupValues?.get(1),
+            )
+        }
+    }
+
+    /** An earlier launch's log, copied to the cache dir for sharing like [shareableFile]. */
+    fun shareableFile(context: Context, past: File): android.net.Uri {
+        val dir = File(context.cacheDir, "shared").apply { mkdirs() }
+        dir.listFiles()?.forEach { it.delete() }
+        val out = File(dir, "gearslip-log-${past.name.removePrefix("gearslip-").removeSuffix(".log")}.txt")
+        past.copyTo(out, overwrite = true)
+        return androidx.core.content.FileProvider.getUriForFile(
+            context, "${context.packageName}.logshare", out,
+        )
     }
 
     fun snapshot(): List<String> = synchronized(live) { live.toList() }

gearslip/src/main/java/app/seb3thehacker/gearslip/GearslipRunner.kt

@@ -2,6 +2,7 @@ package app.seb3thehacker.gearslip
 
 import android.os.Build
 import app.seb3thehacker.gearslip.audio.AudioLink
+import app.seb3thehacker.gearslip.audio.CarAudio
 import app.seb3thehacker.gearslip.audio.CarMic
 import app.seb3thehacker.gearslip.media.CarMediaStatus
 import app.seb3thehacker.gearslip.car.BluetoothAudioCheck
@@ -12,12 +13,18 @@ import app.seb3thehacker.gearslip.car.DirectionsVoice
 import app.seb3thehacker.gearslip.car.CarAssistant
 import app.seb3thehacker.gearslip.car.CarEnvironment
 import app.seb3thehacker.gearslip.car.CarKeys
+import app.seb3thehacker.gearslip.car.ScreenFit
 import app.seb3thehacker.gearslip.car.CarSensors
 import app.seb3thehacker.gearslip.car.CarServices
 import app.seb3thehacker.gearslip.car.CarSettings
+import java.io.IOException
+import app.seb3thehacker.gearslip.protocol.InputProtocol
 import java.io.InputStream
 import java.io.OutputStream
+import java.util.concurrent.Executors
 import java.util.concurrent.FutureTask
+import java.util.concurrent.RejectedExecutionException
+import java.util.concurrent.TimeUnit
 
 /**
  * Drives the phone side of the control-channel handshake far enough to answer one question:
@@ -59,6 +66,7 @@ class GearslipRunner(
     /** Waits for the certificate only when TLS is first needed; see [run]. */
     private val tls: PhoneTls by lazy { identityTask.get() }
     private var authenticationFailed = false
+    private var drainWriterOnExit = false
     @Volatile private var stopped = false
 
     @Volatile private var state = State.WAIT_VERSION
@@ -71,6 +79,12 @@ class GearslipRunner(
     private var vehicleProfile: VehicleProfile? = null
     @Volatile private var videoStarted = false
     private var videoSource: VideoSource? = null
+
+    /** Between the car UI and the encoder when the car squashes the frame (see [screenShape]). */
+    private var stretcher: FrameStretcher? = null
+
+    /** What the car UI draws at when [stretcher] is on; touches are scaled into it. */
+    @Volatile private var drawSize: Pair<Int, Int>? = null
     @Volatile private var inFlight = 0
     /** Guards [inFlight]: the encoder thread waits on it for the head unit's acks. */
     private val ackLock = Object()
@@ -146,6 +160,8 @@ class GearslipRunner(
             reportDisconnect()
         } finally {
             running = false
+            writer.shutdown()
+            if (drainWriterOnExit) writer.awaitTermination(2, TimeUnit.SECONDS)
             writer.shutdownNow()
             log.flush()
         }
@@ -160,6 +176,9 @@ class GearslipRunner(
         synchronized(ackLock) { ackLock.notifyAll() } // free an encoder waiting on an ack
         videoSource?.stop()
         videoSource = null
+        stretcher?.release()
+        stretcher = null
+        CarAudio.openSink = null
         audioLink?.close()
         audioLink = null
         guidanceLink?.close()
@@ -181,7 +200,7 @@ class GearslipRunner(
 
     private fun handleFrame(frame: Frames.Frame) {
         // A rejected handshake cannot consume later messages as if authentication succeeded.
-        if (authenticationFailed || stopped) return
+        if (authenticationFailed || stopped || !running) return
         val payload = if (frame.encrypted) {
             if (!tls.handshakeComplete) {
                 log.w("encrypted frame arrived before the handshake finished - ignoring")
@@ -192,7 +211,10 @@ class GearslipRunner(
             frame.payload
         }
 
-        val message = assembler.offer(frame, payload) ?: return
+        val message = if (frame.messageType == Frames.MESSAGE_CONTROL) {
+            if (frame.frameType != Frames.TYPE_BULK) throw IOException("Fragmented channel control message")
+            payload
+        } else assembler.offer(frame, payload) ?: return
         if (message.size < 2) {
             log.w("runt message on channel ${frame.channel}")
             return
@@ -204,6 +226,7 @@ class GearslipRunner(
         lastProgress = System.currentTimeMillis()
 
         if (frame.channel != Frames.CHANNEL_CONTROL) {
+            if (state != State.DONE || !frame.encrypted) return
             if (frame.channel == videoChannelId) {
                 onVideoMessage(messageId, body)
             } else if (frame.channel == inputChannelId) {
@@ -239,6 +262,9 @@ class GearslipRunner(
             }
             return
         }
+        if (messageId !in setOf(MSG_VERSION_REQUEST, MSG_ENCAPSULATED_SSL, MSG_AUTH_COMPLETE,
+                MSG_BYEBYE_REQUEST, MSG_UNEXPECTED_MESSAGE, MSG_FRAMING_ERROR) &&
+            (!frame.encrypted || state != State.DONE && state != State.WAIT_SDR)) return
 
         when (messageId) {
             MSG_VERSION_REQUEST -> onVersionRequest(body)
@@ -247,11 +273,25 @@ class GearslipRunner(
             MSG_SERVICE_DISCOVERY_RESPONSE -> onServiceDiscoveryResponse(body)
             MSG_PING_REQUEST -> onPingRequest(body)
             MSG_BYEBYE_REQUEST -> onByeByeRequest(body)
-            AudioLink.MSG_FOCUS_RESPONSE -> audioLink?.onFocus(Protobuf.readInt32Field(body, 1) ?: 0)
+            MSG_UNEXPECTED_MESSAGE, MSG_FRAMING_ERROR -> onProtocolError(messageId)
+            AudioLink.MSG_FOCUS_RESPONSE -> {
+                // One answer for both sinks: it is the directions' while they wait on one.
+                val state = Protobuf.readInt32Field(body, 1) ?: 0
+                val guidance = guidanceLink
+                if (guidance != null && guidance.expectsFocusAnswer()) guidance.onFocus(state) else audioLink?.onFocus(state)
+            }
             else -> log.i("unhandled control message id=$messageId (${body.size} bytes) - continuing")
         }
     }
 
+    private fun onProtocolError(messageId: Int) {
+        val detail = if (messageId == MSG_FRAMING_ERROR) "framing error" else "unexpected message"
+        log.w("head unit terminated the protocol: $detail")
+        SessionReport.fail(SessionReport.Category.UNKNOWN, detail, state.name, "protocol $messageId")
+        SessionStatus.failed("Protocol error", "The head unit reported a $detail.")
+        running = false
+    }
+
     /**
      * The head unit asking to end the session. It drops USB a few seconds later whether or not
      * we answer, so the point here is the reason: an Audi MIB2+ sent this about a second after
@@ -265,16 +305,23 @@ class GearslipRunner(
             3 -> "NOT_SUPPORTED"
             4 -> "NOT_CURRENTLY_SUPPORTED"
             5 -> "PROBE_SUPPORTED"
+            6 -> "WIRELESS_PROJECTION_DISABLED"
+            7 -> "POWER_DOWN"
+            8 -> "USER_PROFILE_SWITCH"
             else -> "unknown"
         }
         log.w("<- ByeByeRequest: reason=$reason ($name) in state $state")
         log.hex("   byebye raw", body)
         SessionReport.fail(SessionReport.Category.BYEBYE, "ByeByeRequest reason=$reason ($name)", state.name, "bye $reason")
-        send(MSG_BYEBYE_RESPONSE, ByteArray(0), encrypted = true)
+        send(MSG_BYEBYE_RESPONSE, ByteArray(0), encrypted = state == State.WAIT_SDR || state == State.DONE)
         log.i("-> ByeByeResponse")
+        drainWriterOnExit = true
+        running = false
+        SessionStatus.disconnected()
     }
 
     private fun onVersionRequest(body: ByteArray) {
+        if (state != State.WAIT_VERSION) return
         if (body.size < 4) {
             log.w("VersionRequest too short (${body.size} bytes)")
             return
@@ -284,24 +331,16 @@ class GearslipRunner(
         log.i("<- VersionRequest: head unit speaks $major.$minor")
         SessionReport.protocolVersion(major, minor)
 
-        // Always 1.3, on purpose. Every car that accepts Gearslip was tested this way, 1.5 units
-        // included. Echoing the car's own version was tried too: a 4.3 unit rejected the
-        // certificate either way, so the version doesn't decide acceptance. The log says so, since
-        // a car offering 1.5 and getting 1.3 back looks like a bug to anyone reading it.
-        val claim = CLAIM_VERSION ?: (major to minor)
-        val response = byteArrayOf(
-            ((claim.first shr 8) and 0xFF).toByte(), (claim.first and 0xFF).toByte(),
-            ((claim.second shr 8) and 0xFF).toByte(), (claim.second and 0xFF).toByte(),
-            0, 0, // STATUS_SUCCESS
-        )
-        send(MSG_VERSION_RESPONSE, response, encrypted = false)
-        log.i(
-            "-> VersionResponse: ${claim.first}.${claim.second} status=0 (STATUS_SUCCESS)" +
-                if (CLAIM_VERSION != null && claim != (major to minor)) {
-                    " - intended: Gearslip always answers ${claim.first}.${claim.second}, which cars " +
-                        "offering $major.$minor accept too"
-                } else "",
-        )
+        val response = ProtocolVersion.respond(major, minor)
+        send(MSG_VERSION_RESPONSE, response.bytes, encrypted = false)
+        log.i("-> VersionResponse: ${response.major}.${response.minor}, supported=${response.supported}")
+        if (!response.supported) {
+            authenticationFailed = true
+            drainWriterOnExit = true
+            running = false
+            SessionStatus.failed("Unsupported protocol", "The head unit requested protocol $major.$minor.")
+            return
+        }
         state = State.TLS_HANDSHAKE
         SessionStatus.connecting("Securing the link")
         log.i("awaiting ClientHello - the head unit is the TLS client, we are the server")
@@ -318,17 +357,13 @@ class GearslipRunner(
             if (stopped) return
             log.e("TLS handshake threw", t)
             SessionReport.fail(SessionReport.Category.TLS, "handshake threw", t, state.name)
-            log.verdict(
-                "NOT VIABLE (TLS rejected)",
-                "The head unit aborted the TLS handshake. A bad_certificate / unknown_ca / " +
-                    "handshake_failure alert here means it validates the phone's certificate.",
-            )
             SessionStatus.failed(
-                "Head unit rejected the certificate",
-                "The head unit aborted the secure handshake. It validates the phone's certificate.",
+                "Secure connection failed",
+                "The secure handshake could not be completed. Check the session log for details.",
             )
             state = State.DONE
             authenticationFailed = true
+            running = false
             SessionReport.print()
             return
         }
@@ -345,7 +380,7 @@ class GearslipRunner(
 
     private fun onAuthComplete(body: ByteArray) {
         val status = Protobuf.readInt32Field(body, 1)
-        if (state != State.WAIT_AUTH && !(state == State.TLS_HANDSHAKE && status in listOf(-2, -3))) return
+        if (state != State.WAIT_AUTH && !(state == State.TLS_HANDSHAKE && status != null && status != 0)) return
         log.i("<- AuthComplete: status=$status")
         status?.let { SessionReport.auth(it) }
 
@@ -356,17 +391,17 @@ class GearslipRunner(
                 SessionStatus.connecting("Certificate accepted - discovering services")
                 sendServiceDiscoveryRequest()
             }
-            -2 -> {
-                SessionReport.fail(SessionReport.Category.CERTIFICATE, "AuthComplete status -2 (certificate error)", state.name, "auth -2")
-                log.verdict(
-                    "NOT VIABLE (STATUS_CERTIFICATE_ERROR)",
-                    "The head unit explicitly rejected the phone's self-signed certificate. " +
-                        "This is a definitive no - it validates the phone against a trust chain " +
-                        "we cannot issue from.",
-                )
+            -2, -23, -24 -> {
+                val reason = when (status) {
+                    -23 -> "The phone's certificate is not valid yet."
+                    -24 -> "The phone's certificate has expired."
+                    else -> "The head unit refused the phone's certificate."
+                }
+                SessionReport.fail(SessionReport.Category.CERTIFICATE, "AuthComplete status $status", state.name, "auth $status")
+                log.w("certificate rejected: $reason")
                 SessionStatus.failed(
                     "Head unit rejected the certificate",
-                    "The head unit refused the phone's certificate (certificate error).",
+                    reason,
                 )
                 state = State.DONE
                 authenticationFailed = true
@@ -397,6 +432,7 @@ class GearslipRunner(
                 authenticationFailed = true
             }
         }
+        if (authenticationFailed) running = false
     }
 
     private fun sendServiceDiscoveryRequest() {
@@ -407,6 +443,7 @@ class GearslipRunner(
     }
 
     private fun onServiceDiscoveryResponse(body: ByteArray) {
+        if (state != State.WAIT_SDR) return
         log.i("<- ServiceDiscoveryResponse (${body.size} bytes, decrypted successfully)")
         // Field 5 is the car's serial number, and the Bluetooth service carries the car's
         // Bluetooth address. Either one identifies the car, and logs get shared, so both stay out.
@@ -527,7 +564,17 @@ class GearslipRunner(
             // as Android Auto does, instead of letting it play on to no one.
             onTakenBack = { CarServices.pausePhoneMedia("the car switched to another source") },
         )
-        openChannel(media.serviceId)
+        if (CarSettings.pipeAudio.value) {
+            openChannel(media.serviceId)
+        } else {
+            // Many cars switch their source to Android Auto the moment this channel opens, which
+            // cut off music the driver chose to play over Bluetooth. Open it only if they switch.
+            log.i("music goes over Bluetooth: the media channel stays closed, so the car keeps its own source")
+            CarAudio.openSink = {
+                CarAudio.openSink = null
+                openChannel(media.serviceId)
+            }
+        }
     }
 
     /** The car's directions channel, where [DirectionsVoice] reads out each turn. */
@@ -545,7 +592,7 @@ class GearslipRunner(
             tag = "guidance",
             sessionId = GUIDANCE_SESSION_ID,
             asksFocus = false,
-            onReady = { DirectionsVoice.attach(it) },
+            onReady = { DirectionsVoice.attach(it) { audioLink?.streaming == true } },
             onClose = { DirectionsVoice.detach(it) },
         )
         openChannel(guidance.serviceId)
@@ -619,12 +666,15 @@ class GearslipRunner(
 
     /** Turn-by-turn for the instrument cluster: the next turn, its road, and how far. */
     private fun startClusterNavChannel(serviceDiscoveryResponse: ByteArray) {
-        val channel = ServiceDiscovery.findNavStatusChannel(serviceDiscoveryResponse) ?: run {
+        val navigation = ServiceDiscovery.findNavStatusService(serviceDiscoveryResponse) ?: run {
             log.i("no navigation status channel - the cluster won't show turns")
             return
         }
+        val channel = navigation.serviceId
         log.i("navigation status channel: $channel")
-        clusterNav = ClusterNav(channel) { id, body -> send(id, body, encrypted = true, channel = channel) }
+        clusterNav = ClusterNav(channel, navigation.minimumIntervalMs.toLong()) { id, body ->
+            send(id, body, encrypted = true, channel = channel)
+        }
         openChannel(channel)
     }
 
@@ -680,7 +730,7 @@ class GearslipRunner(
      */
     private fun onNightSensor(body: ByteArray) {
         val night = Wire.bytes(Wire.fields(body), SENSOR_NIGHT) ?: return
-        val isNight = Wire.varint(Wire.fields(night), 1) == 1L
+        val isNight = (Wire.varint(Wire.fields(night), 1) ?: 0L) != 0L
         if (isNight != lastSensorNight) {
             lastSensorNight = isNight
             log.i("car says it's ${if (isNight) "night" else "day"}")
@@ -763,59 +813,60 @@ class GearslipRunner(
             MSG_KEY_BINDING_RESPONSE ->
                 log.i("<- KeyBindingResponse: status=${Protobuf.readInt32Field(body, 1)}")
 
-            MSG_INPUT_REPORT -> {
-                val report = Wire.fields(body)
-                // The 2018 Uconnect agrees to Exit but keeps showing our last frame and sending
-                // touches, which looked like a crash. A touch means our screen is still up there.
-                if (videoStarted && !videoProjected && Wire.bytes(report, 3) != null) {
-                    log.w("the car said it took its screen back but still sends touches - showing ours again")
-                    onVideoFocus(VIDEO_FOCUS_PROJECTED)
-                }
-                Wire.bytes(report, 4)?.let(::onKeyEvent)
-                Wire.bytes(report, 6)?.let(::onRelativeEvent)
-                val touch = Wire.bytes(report, 3) ?: Wire.bytes(report, 7)
-                if (touch == null) {
-                    return
-                }
-                val touchFields = Wire.fields(touch)
-                val action = Wire.varint(touchFields, 3)?.toInt() ?: 0
-                val pointers = Wire.allBytes(touchFields, 1)
-                if (pointers.isEmpty()) return
-                val config = videoConfigs.getOrNull(selectedConfigIndex ?: 0)
-                val size = config?.pixelSize()
-                // The car crops its margin off the frame and measures taps from the corner of what
-                // it shows, so they come in short by half the margin: the 2024 VW (margin 240) sent
-                // y=6, which is inside the cropped band, and the Uconnect's never passed 351 on a
-                // 480-high frame with a 130 margin. Without this every tap landed 120 px too high
-                // and the VW couldn't press past its first screen.
-                val shift = config?.marginInsets() ?: Insets.NONE
-                val points = pointers.mapIndexedNotNull { index, pointer ->
-                    val fields = Wire.fields(pointer)
-                    val rawX = Wire.varint(fields, 1)?.toInt() ?: return@mapIndexedNotNull null
-                    val rawY = Wire.varint(fields, 2)?.toInt() ?: return@mapIndexedNotNull null
-                    val id = Wire.varint(fields, 3)?.toInt() ?: index
-                    TouchPoint(id, clamp(rawX + shift.left, size?.first), clamp(rawY + shift.top, size?.second))
-                }
-                if (points.isEmpty()) return
-                val actionIndex = (Wire.varint(touchFields, 2)?.toInt() ?: 0).coerceIn(0, points.size - 1)
-                if (points.size > 1 && touchesSeen < 3) {
-                    log.i("multi-touch: ${points.size} pointers, action=$action index=$actionIndex")
-                }
-
-                touchesSeen++
-                if (touchesSeen <= 10 || action == ACTION_DOWN || action == ACTION_UP) {
-                    val at = points[actionIndex]
-                    log.i("<- Touch action=$action at (${at.x.toInt()},${at.y.toInt()}) pointers=${points.size}")
-                }
-                // Time the next frame against this tap: see [reportTouchLatency].
-                if (action == ACTION_DOWN || action == ACTION_UP) touchAtUs = System.nanoTime() / 1000
-                projection?.onTouch(action, actionIndex, points)
-            }
+            MSG_INPUT_REPORT -> onInputReport(body)
 
             else -> log.i("<- unhandled input message id=$messageId (${body.size} bytes)")
         }
     }
 
+    private fun onInputReport(body: ByteArray) {
+        val report = Wire.fields(body)
+        if (Wire.varint(report, 1) == null) return
+        Wire.bytes(report, 4)?.let(::onKeyEvent)
+        Wire.bytes(report, 6)?.let(::onRelativeEvent)
+        // Touchpads (field 7) need a separate gesture pipeline; their coordinates are not
+        // positions on the projected screen.
+        val touch = Wire.bytes(report, 3)
+        if (touch == null) {
+            return
+        }
+        // The 2018 Uconnect agrees to Exit but keeps showing our last frame and sending
+        // touches, which looked like a crash. A touch means our screen is still up there.
+        if (videoStarted && !videoProjected) {
+            log.w("the car said it took its screen back but still sends touches - showing ours again")
+            onVideoFocus(VIDEO_FOCUS_PROJECTED)
+        }
+        val config = videoConfigs.getOrNull(selectedConfigIndex ?: 0)
+        // The car crops its margin off the frame and measures taps from the corner of what it
+        // shows, so they come in short by half the margin: the 2024 VW (margin 240) sent y=6,
+        // inside the cropped band, and the Uconnect's never passed 351 on a 480-high frame with a
+        // 130 margin. Without this every tap landed 120 px too high.
+        val shift = config?.let(::marginsFor) ?: Insets.NONE
+        val size = config?.pixelSize()
+        // A stretched frame (see [screenShape]): the car's tap is on the frame, the UI is drawn smaller.
+        val drawn = drawSize
+        val stretched = drawn != null && size != null
+        val (action, actionIndex, raw) =
+            (if (stretched) InputProtocol.touch(touch, size) else InputProtocol.touch(touch, size, shift.left, shift.top)) ?: return
+        val points = if (drawn != null && size != null) {
+            raw.map { TouchPoint(it.id, it.x * drawn.first / size.first, it.y * drawn.second / size.second) }
+        } else {
+            raw
+        }
+        if (points.size > 1 && touchesSeen < 3) {
+            log.i("multi-touch: ${points.size} pointers, action=$action index=$actionIndex")
+        }
+
+        touchesSeen++
+        if (touchesSeen <= 10 || action == ACTION_DOWN || action == ACTION_UP) {
+            val at = points[actionIndex]
+            log.i("<- Touch action=$action at (${at.x.toInt()},${at.y.toInt()}) pointers=${points.size}")
+        }
+        // Time the next frame against this tap: see [reportTouchLatency].
+        if (action == ACTION_DOWN || action == ACTION_UP) touchAtUs = System.nanoTime() / 1000
+        projection?.onTouch(action, actionIndex, points)
+    }
+
     /**
      * Asks the head unit to forward its buttons. Many units send nothing from the steering wheel
      * until the phone names the keys it wants. What the unit offered is asked for; a unit that
@@ -967,6 +1018,37 @@ class GearslipRunner(
         return wide.minByOrNull(::pixels) ?: known.maxByOrNull(::pixels)
     }
 
+    /**
+     * The part of a [frameWidth] x [frameHeight] frame shaped like the screen size set in
+     * Settings, centred and in even pixels; null when none is set or it is the frame's own shape.
+     * Some head units report the wrong size, then crop or squash the frame onto their real screen.
+     */
+    private fun screenShape(frameWidth: Int, frameHeight: Int): Pair<Int, Int>? {
+        val screen = CarSettings.screenSize.value ?: return null
+        val wider = screen.width.toLong() * frameHeight >= screen.height.toLong() * frameWidth
+        val shape = if (wider) {
+            frameWidth to (frameWidth.toLong() * screen.height / screen.width).toInt()
+        } else {
+            (frameHeight.toLong() * screen.width / screen.height).toInt() to frameHeight
+        }
+        val even = (shape.first / 2 * 2).coerceAtLeast(2) to (shape.second / 2 * 2).coerceAtLeast(2)
+        return even.takeIf { it != (frameWidth to frameHeight) }
+    }
+
+    /**
+     * The strips of the frame the car doesn't show: the head unit's own margins, or, when a screen
+     * size is set to crop, whatever lies outside [screenShape]. The UI keeps out of them and taps
+     * are measured from inside them.
+     */
+    private fun marginsFor(config: ServiceDiscovery.VideoConfig): Insets {
+        val (width, height) = config.pixelSize() ?: return config.marginInsets()
+        if (CarSettings.screenFit.value != ScreenFit.CROP) return config.marginInsets()
+        val (w, h) = screenShape(width, height) ?: return config.marginInsets()
+        val sideX = width - w
+        val sideY = height - h
+        return Insets(top = sideY / 2, bottom = sideY - sideY / 2, left = sideX / 2, right = sideX - sideX / 2)
+    }
+
     private fun startVideoSource() {
         lastKeyframeSentAt = System.currentTimeMillis() // frame #1 is always a keyframe
         val index = selectedConfigIndex ?: 0
@@ -987,8 +1069,21 @@ class GearslipRunner(
         log.i("-> Start(session_id=$SESSION_ID, configuration_index=$index -> $config)")
         // The car crops its margins off the frame, so keep the UI out of them unless a vehicle
         // profile has its own tuned insets.
-        if (vehicleProfile?.insets.let { it == null || it == Insets.NONE }) {
-            val insets = config.marginInsets()
+        stretcher?.release()
+        stretcher = null
+        drawSize = null
+        val shape = screenShape(width, height)
+        val squash = shape != null && CarSettings.screenFit.value == ScreenFit.SQUASH
+        if (shape != null) {
+            log.i(
+                "screen size set to ${CarSettings.screenSize.value} in Settings: " +
+                    "${if (squash) "drawing" else "cropping to"} ${shape.first}x${shape.second} of the ${width}x$height frame",
+            )
+        }
+        if (squash) {
+            CarEnvironment.setInsets(Insets.NONE)
+        } else if (vehicleProfile?.insets.let { it == null || it == Insets.NONE }) {
+            val insets = marginsFor(config)
             CarEnvironment.setInsets(insets)
             if (insets != Insets.NONE) log.i("keeping the UI clear of the car's margins: $insets")
         }
@@ -1015,7 +1110,16 @@ class GearslipRunner(
                 source.start()
                 val surface = source.inputSurface
                 if (projection != null && surface != null) {
-                    projection.onSurfaceReady(surface, width, height, config.density)
+                    val stretch = shape?.takeIf { squash }?.let { (w, h) ->
+                        FrameStretcher(surface, w, h, width, height).takeIf { it.start() }
+                    }
+                    stretcher = stretch
+                    if (stretch != null) {
+                        drawSize = stretch.width to stretch.height
+                        projection.onSurfaceReady(stretch.input, stretch.width, stretch.height, config.density)
+                    } else {
+                        projection.onSurfaceReady(surface, width, height, config.density)
+                    }
                     SessionStatus.projecting()
                     BluetoothAudioCheck.onProjecting()
                     LocationCheck.onProjecting()
@@ -1156,18 +1260,15 @@ class GearslipRunner(
         log.i("touch -> frame: ${draw + encode}ms (draw ${draw}ms, encode and wait ${encode}ms)")
     }
 
-    private fun clamp(value: Int, limit: Int?): Float = when {
-        limit == null -> value.toFloat()
-        value < 0 -> 0f
-        value >= limit -> (limit - 1).toFloat()
-        else -> value.toFloat()
-    }
-
     private fun onPingRequest(body: ByteArray) {
         // The timestamp is an int64 and has to come back unchanged. Read as an int32 it was cut
         // short, and a car that checks the echo (an Audi MIB2+) gave up at its second ping.
-        val timestamp = Protobuf.readInt64Field(body, 1) ?: System.nanoTime()
-        send(MSG_PING_RESPONSE, Protobuf.varintField(1, timestamp), encrypted = tls.handshakeComplete)
+        val fields = Wire.fields(body)
+        val timestamp = Wire.varint(fields, 1) ?: return
+        val payload = Wire.bytes(fields, 3)
+        val response = Protobuf.varintField(1, timestamp) +
+            (payload?.let { Protobuf.bytesField(2, it) } ?: byteArrayOf())
+        send(MSG_PING_RESPONSE, response, encrypted = tls.handshakeComplete)
         log.i("<- PingRequest(timestamp=$timestamp) / -> PingResponse (keeping the session alive)")
     }
 
@@ -1189,41 +1290,16 @@ class GearslipRunner(
         try {
             writer.execute {
                 try {
-                    if (payload.size <= Frames.MAX_FRAME_PAYLOAD) {
-                        val framePayload = if (encrypted) tls.encrypt(payload) else payload
-                        output.write(Frames.build(channel, encrypted, framePayload, messageType))
-                    } else {
-                        // Split exactly as aasdk does: chunk the *plaintext*, encrypt each chunk
-                        // separately, and carry the total plaintext length in the FIRST frame.
-                        // Video keyframes for anything busier than a test card exceed 16 KB routinely.
-                        var offset = 0
-                        while (offset < payload.size) {
-                            val size = minOf(Frames.MAX_FRAME_PAYLOAD, payload.size - offset)
-                            val chunk = payload.copyOfRange(offset, offset + size)
-                            val frameType = when {
-                                offset == 0 -> Frames.TYPE_FIRST
-                                offset + size >= payload.size -> Frames.TYPE_LAST
-                                else -> Frames.TYPE_MIDDLE
-                            }
-                            val framePayload = if (encrypted) tls.encrypt(chunk) else chunk
-                            output.write(
-                                Frames.build(
-                                    channel, encrypted, framePayload, messageType, frameType,
-                                    if (frameType == Frames.TYPE_FIRST) payload.size else null,
-                                ),
-                            )
-                            offset += size
-                        }
-                        splitMessages++
-                    }
+                    val frameCount = Frames.writeMessage(output, channel, encrypted, messageType, payload) { tls.encrypt(it) }
+                    if (frameCount > 1) splitMessages++
                     output.flush()
-                } catch (e: java.io.IOException) {
+                } catch (e: IOException) {
                     if (running) log.w("send failed, stopping: ${e.message}")
                     running = false
                     videoSource?.stop()
                 }
             }
-        } catch (e: java.util.concurrent.RejectedExecutionException) {
+        } catch (e: RejectedExecutionException) {
             // The session is over; nothing more goes out.
         }
     }
@@ -1319,13 +1395,6 @@ class GearslipRunner(
     }
 
     private companion object {
-        /**
-         * The protocol version Gearslip answers every car with, as (major, minor), or null to echo
-         * the head unit's. Kept at 1.3 because every working car was tested with it; see
-         * onVersionRequest.
-         */
-        val CLAIM_VERSION: Pair<Int, Int>? = 1 to 3
-
         // protobuf/aap_protobuf/service/control/ControlMessageType.proto:7-17
         const val MSG_VERSION_REQUEST = 1
         const val MSG_VERSION_RESPONSE = 2
@@ -1338,6 +1407,8 @@ class GearslipRunner(
         const val MSG_BYEBYE_REQUEST = 15
         const val MSG_BYEBYE_RESPONSE = 16
         const val MSG_VOICE_SESSION_NOTIFICATION = 17
+        const val MSG_UNEXPECTED_MESSAGE = 255
+        const val MSG_FRAMING_ERROR = 65535
         const val MSG_CHANNEL_OPEN_REQUEST = 7
         const val MSG_CHANNEL_OPEN_RESPONSE = 8
 

gearslip/src/main/java/app/seb3thehacker/gearslip/PhoneTls.kt

@@ -1,5 +1,6 @@
 package app.seb3thehacker.gearslip
 
+import java.io.ByteArrayOutputStream
 import java.net.Socket
 import java.nio.ByteBuffer
 import java.security.KeyStore
@@ -11,23 +12,10 @@ import javax.net.ssl.SSLEngine
 import javax.net.ssl.SSLEngineResult
 import javax.net.ssl.SSLEngineResult.HandshakeStatus
 import javax.net.ssl.SSLPeerUnverifiedException
+import javax.net.ssl.SSLException
 import javax.net.ssl.X509ExtendedTrustManager
 
-/**
- * The phone end of the Android Auto TLS session.
- *
- * Two things here are the opposite of what aasdk does, because aasdk implements the head
- * unit and the head unit is the TLS *client*: it calls TLS_client_method() and
- * SSL_set_connect_state (src/Transport/SSLWrapper.cpp:97-140, src/Messenger/Cryptor.cpp:87),
- * and SSL_set_accept_state appears nowhere in that codebase. So the phone is the TLS
- * **server** and its certificate goes out as the server certificate - sent unconditionally
- * on every handshake, which is precisely what we are testing.
- *
- * TLS here is not layered over the socket: handshake bytes travel inside
- * MESSAGE_ENCAPSULATED_SSL control messages (id 3). That rules out SSLSocket and makes
- * SSLEngine - a buffer-to-buffer engine, the JSSE counterpart of aasdk's memory BIO pair -
- * the right tool.
- */
+/** TLS server for projection. Handshake records travel in control message 3, not a TLS socket. */
 class PhoneTls(keyStore: KeyStore, password: CharArray) {
     private val log = GearslipLog.tagged("TLS")
 
@@ -36,7 +24,7 @@ class PhoneTls(keyStore: KeyStore, password: CharArray) {
     private var appBuffer = ByteBuffer.allocate(32 * 1024)
     private var netBuffer = ByteBuffer.allocate(32 * 1024)
 
-    var handshakeComplete: Boolean = false
+    @Volatile var handshakeComplete: Boolean = false
         private set
 
     init {
@@ -52,6 +40,7 @@ class PhoneTls(keyStore: KeyStore, password: CharArray) {
             useClientMode = false
             // want, not need: we ask the head unit for its certificate so the run also tells
             // us what real units present, but we never make the session depend on getting one.
+            // Homemade head units may have none.
             wantClientAuth = true
             enabledProtocols = arrayOf("TLSv1.2") // aasdk pins TLS 1.2
         }
@@ -88,7 +77,7 @@ class PhoneTls(keyStore: KeyStore, password: CharArray) {
                     if (netBuffer.hasRemaining()) {
                         outgoing += ByteArray(netBuffer.remaining()).also { netBuffer.get(it) }
                     }
-                    if (result.status == SSLEngineResult.Status.CLOSED) break@loop
+                    if (result.status == SSLEngineResult.Status.CLOSED) throw SSLException("TLS closed during handshake")
                 }
 
                 HandshakeStatus.NEED_UNWRAP -> {
@@ -100,7 +89,7 @@ class PhoneTls(keyStore: KeyStore, password: CharArray) {
                             appBuffer = ByteBuffer.allocate(appBuffer.capacity() * 2)
                             continue@loop
                         }
-                        SSLEngineResult.Status.CLOSED -> break@loop
+                        SSLEngineResult.Status.CLOSED -> throw SSLException("TLS closed during handshake")
                         else -> Unit
                     }
                 }
@@ -124,7 +113,7 @@ class PhoneTls(keyStore: KeyStore, password: CharArray) {
     /** Wraps a control-channel payload for an ENCRYPTED frame. */
     fun encrypt(plain: ByteArray): ByteArray {
         val source = ByteBuffer.wrap(plain)
-        val out = java.io.ByteArrayOutputStream()
+        val out = ByteArrayOutputStream()
         while (source.hasRemaining()) {
             netBuffer.clear()
             val result = engine.wrap(source, netBuffer)
@@ -132,6 +121,9 @@ class PhoneTls(keyStore: KeyStore, password: CharArray) {
                 netBuffer = ByteBuffer.allocate(netBuffer.capacity() * 2)
                 continue
             }
+            if (result.status != SSLEngineResult.Status.OK || result.bytesConsumed() == 0) {
+                throw SSLException("TLS could not encrypt application data: ${result.status}")
+            }
             netBuffer.flip()
             val chunk = ByteArray(netBuffer.remaining())
             netBuffer.get(chunk)
@@ -140,14 +132,10 @@ class PhoneTls(keyStore: KeyStore, password: CharArray) {
         return out.toByteArray()
     }
 
-    /**
-     * Unwraps one ENCRYPTED frame's payload. aasdk decrypts per frame
-     * (MessageOutStream::compoundFrame encrypts per frame), so each frame's payload is
-     * self-contained ciphertext.
-     */
+    /** Each encrypted projection frame contains complete TLS records. */
     fun decrypt(cipher: ByteArray): ByteArray {
         val source = ByteBuffer.wrap(cipher)
-        val out = java.io.ByteArrayOutputStream()
+        val out = ByteArrayOutputStream()
         while (source.hasRemaining()) {
             appBuffer.clear()
             val result = engine.unwrap(source, appBuffer)
@@ -157,10 +145,9 @@ class PhoneTls(keyStore: KeyStore, password: CharArray) {
                     continue
                 }
                 SSLEngineResult.Status.BUFFER_UNDERFLOW -> {
-                    log.w("decrypt: record split across frames (${source.remaining()} bytes left over)")
-                    break
+                    throw SSLException("Incomplete TLS record in an encrypted frame")
                 }
-                SSLEngineResult.Status.CLOSED -> break
+                SSLEngineResult.Status.CLOSED -> throw SSLException("TLS peer closed the connection")
                 else -> Unit
             }
             appBuffer.flip()

gearslip/src/main/java/app/seb3thehacker/gearslip/Protobuf.kt

@@ -2,14 +2,7 @@ package app.seb3thehacker.gearslip
 
 import java.io.ByteArrayOutputStream
 
-/**
- * Just enough protobuf to run the spike, hand-rolled so there is no protoc step.
- *
- * Only three messages are ever written (AuthResponse is only read):
- *   ServiceDiscoveryRequest { optional string label_text = 4; optional string device_name = 5; }
- *   PingResponse            { required int64 timestamp = 1; }
- *   AuthResponse            { required int32 status = 1; }
- */
+/** Protobuf field encoding and diagnostic rendering for the projection protocol. */
 object Protobuf {
 
     fun varint(value: Long): ByteArray {
@@ -41,29 +34,7 @@ object Protobuf {
     fun readInt32Field(data: ByteArray, field: Int): Int? = readInt64Field(data, field)?.toInt()
 
     /** Reads a varint field whole, for int64s such as a ping's timestamp. */
-    fun readInt64Field(data: ByteArray, field: Int): Long? {
-        var pos = 0
-        while (pos < data.size) {
-            val (tag, afterTag) = readVarint(data, pos) ?: return null
-            pos = afterTag
-            val number = (tag ushr 3).toInt()
-            when ((tag and 7L).toInt()) {
-                0 -> {
-                    val (value, afterValue) = readVarint(data, pos) ?: return null
-                    pos = afterValue
-                    if (number == field) return value
-                }
-                2 -> {
-                    val (len, afterLen) = readVarint(data, pos) ?: return null
-                    pos = afterLen + len.toInt()
-                }
-                5 -> pos += 4
-                1 -> pos += 8
-                else -> return null
-            }
-        }
-        return null
-    }
+    fun readInt64Field(data: ByteArray, field: Int): Long? = Wire.varint(Wire.fields(data), field)
 
     /**
      * Shallow field dump. Used on ServiceDiscoveryResponse: its make/model/year strings
@@ -71,6 +42,7 @@ object Protobuf {
      * proof that the session is live and we are decrypting correctly.
      */
     fun describe(data: ByteArray, indent: String = "  "): String {
+        if (indent.length > 32) return "$indent(nested message)\n"
         val sb = StringBuilder()
         var pos = 0
         while (pos < data.size) {
@@ -89,6 +61,7 @@ object Protobuf {
                 }
                 2 -> {
                     val (len, afterLen) = readVarint(data, pos) ?: break
+                    if (len < 0 || len > data.size - afterLen) break
                     val end = afterLen + len.toInt()
                     if (end > data.size) break
                     val body = data.copyOfRange(afterLen, end)
@@ -117,6 +90,7 @@ object Protobuf {
         var pos = start
         while (pos < data.size && shift <= 63) {
             val b = data[pos].toInt() and 0xFF
+            if (shift == 63 && b > 1) return null
             result = result or ((b and 0x7F).toLong() shl shift)
             pos++
             if (b and 0x80 == 0) return result to pos
@@ -135,45 +109,68 @@ object Wire {
         val out = mutableListOf<Field>()
         var pos = 0
         while (pos < data.size) {
-            val tag = readVarint(data, pos) ?: break
+            val tag = readVarint(data, pos) ?: return emptyList()
             pos = tag.second
             val number = (tag.first ushr 3).toInt()
+            if (tag.first ushr 3 !in 1..0x1fff_ffffL) return emptyList()
             when ((tag.first and 7L).toInt()) {
                 0 -> {
-                    val v = readVarint(data, pos) ?: break
+                    val v = readVarint(data, pos) ?: return emptyList()
                     pos = v.second
                     out += Field(number, 0, v.first, null)
                 }
-                1 -> { if (pos + 8 > data.size) break; pos += 8 }
+                1 -> { if (data.size - pos < 8) return emptyList(); pos += 8 }
                 2 -> {
-                    val len = readVarint(data, pos) ?: break
+                    val len = readVarint(data, pos) ?: return emptyList()
+                    if (len.first < 0 || len.first > data.size - len.second) return emptyList()
                     val end = len.second + len.first.toInt()
-                    if (end > data.size || end < len.second) break
+                    if (end > data.size || end < len.second) return emptyList()
                     out += Field(number, 2, 0, data.copyOfRange(len.second, end))
                     pos = end
                 }
-                5 -> { if (pos + 4 > data.size) break; pos += 4 }
-                else -> break
+                5 -> { if (data.size - pos < 4) return emptyList(); pos += 4 }
+                else -> return emptyList()
             }
         }
         return out
     }
 
     fun varint(fields: List<Field>, number: Int): Long? =
-        fields.firstOrNull { it.number == number && it.wireType == 0 }?.varint
+        fields.lastOrNull { it.number == number && it.wireType == 0 }?.varint
 
     fun bytes(fields: List<Field>, number: Int): ByteArray? =
-        fields.firstOrNull { it.number == number && it.wireType == 2 }?.bytes
+        fields.lastOrNull { it.number == number && it.wireType == 2 }?.bytes
 
     fun allBytes(fields: List<Field>, number: Int): List<ByteArray> =
         fields.filter { it.number == number && it.wireType == 2 }.mapNotNull { it.bytes }
 
+    /** Protobuf readers accept both packed and unpacked repeated numeric fields. */
+    fun repeatedInts(fields: List<Field>, number: Int): List<Int> =
+        repeatedLongs(fields, number)?.map(Long::toInt).orEmpty()
+
+    /** Null means a packed field contained an incomplete or overflowing varint. */
+    fun repeatedLongs(fields: List<Field>, number: Int): List<Long>? = buildList {
+        for (field in fields.filter { it.number == number }) {
+            if (field.wireType == 0) add(field.varint)
+            else if (field.wireType == 2) {
+                val bytes = field.bytes ?: continue
+                var position = 0
+                while (position < bytes.size) {
+                    val (value, next) = readVarint(bytes, position) ?: return null
+                    add(value)
+                    position = next
+                }
+            }
+        }
+    }
+
     private fun readVarint(data: ByteArray, start: Int): Pair<Long, Int>? {
         var result = 0L
         var shift = 0
         var pos = start
         while (pos < data.size && shift <= 63) {
             val b = data[pos].toInt() and 0xFF
+            if (shift == 63 && b > 1) return null
             result = result or ((b and 0x7F).toLong() shl shift)
             pos++
             if (b and 0x80 == 0) return result to pos

gearslip/src/main/java/app/seb3thehacker/gearslip/ProtocolVersion.kt

@@ -0,0 +1,17 @@
+package app.seb3thehacker.gearslip
+
+/**
+ * Advertises our supported 1.x version, as Android Auto does for older head units. Head units that
+ * offer a newer major version (LIVI asks for 6.1, a RAV4 and the DHU for 4.2) still accept a 1.x
+ * answer, so only a major version of 0 is refused.
+ */
+internal object ProtocolVersion {
+    data class Response(val major: Int, val minor: Int, val supported: Boolean) {
+        val bytes: ByteArray get() = byteArrayOf(
+            (major ushr 8).toByte(), major.toByte(), (minor ushr 8).toByte(), minor.toByte(),
+            if (supported) 0 else -1, if (supported) 0 else -1,
+        )
+    }
+
+    fun respond(major: Int, minor: Int): Response = Response(1, 7, major >= 1 && minor in 0..0xffff)
+}

gearslip/src/main/java/app/seb3thehacker/gearslip/ScreenProjector.kt

@@ -51,7 +51,7 @@ class ScreenProjector(private val context: Context) {
      * preview passes "gearslip-preview".
      */
     fun start(
-        surface: Surface,
+        surface: Surface?,
         width: Int,
         height: Int,
         densityDpi: Int,
@@ -219,6 +219,14 @@ class ScreenProjector(private val context: Context) {
         target.dispatchKeyEvent(event)
     }
 
+    /**
+     * Points the display at another surface, or none, without restarting what it shows. The
+     * preview's SurfaceView comes and goes as the phone turns; the car UI on it carries on.
+     */
+    fun setSurface(surface: Surface?) {
+        virtualDisplay?.surface = surface
+    }
+
     fun stop() {
         runCatching { presentation?.dismiss() }
         runCatching { owner?.destroy() }

gearslip/src/main/java/app/seb3thehacker/gearslip/ServiceDiscovery.kt

@@ -76,7 +76,7 @@ object ServiceDiscovery {
     fun findAudioServices(response: ByteArray): List<AudioService> = buildList {
         for (channel in Wire.allBytes(Wire.fields(response), 1)) {
             val service = Wire.fields(channel)
-            val id = Wire.varint(service, 1)?.toInt() ?: continue
+            val id = serviceId(service) ?: continue
             val sink = Wire.bytes(service, 3) ?: continue
             val sinkFields = Wire.fields(sink)
             val audioConfigs = Wire.allBytes(sinkFields, 3)
@@ -116,13 +116,26 @@ object ServiceDiscovery {
      */
     fun findMediaStatusChannel(response: ByteArray): Int? = findChannelWith(response, 9)
 
-    /** The instrument cluster's turn-by-turn channel (NavigationStatusService, Service field 8). */
-    fun findNavStatusChannel(response: ByteArray): Int? = findChannelWith(response, 8)
+    class NavStatusService(val serviceId: Int, val minimumIntervalMs: Int)
+
+    /** The cluster advertises its minimum update interval in NavigationStatusService field 1. */
+    fun findNavStatusService(response: ByteArray): NavStatusService? =
+        Wire.allBytes(Wire.fields(response), 1).firstNotNullOfOrNull { channel ->
+            val service = Wire.fields(channel)
+            val id = serviceId(service) ?: return@firstNotNullOfOrNull null
+            val navigation = Wire.bytes(service, 8) ?: return@firstNotNullOfOrNull null
+            val interval = Wire.varint(Wire.fields(navigation), 1) ?: return@firstNotNullOfOrNull null
+            if (interval !in 0L..Int.MAX_VALUE.toLong()) return@firstNotNullOfOrNull null
+            NavStatusService(id, interval.toInt())
+        }
+
+    private fun serviceId(fields: List<Wire.Field>): Int? =
+        Wire.varint(fields, 1)?.takeIf { it in 1L..255L }?.toInt()
 
     private fun findChannelWith(response: ByteArray, serviceField: Int): Int? =
         Wire.allBytes(Wire.fields(response), 1).firstNotNullOfOrNull { channel ->
             val service = Wire.fields(channel)
-            if (service.any { it.number == serviceField }) Wire.varint(service, 1)?.toInt() else null
+            if (Wire.bytes(service, serviceField) != null) serviceId(service) else null
         }
 
     /**
@@ -134,7 +147,7 @@ object ServiceDiscovery {
     fun findMicService(response: ByteArray): AudioService? {
         for (channel in Wire.allBytes(Wire.fields(response), 1)) {
             val service = Wire.fields(channel)
-            val id = Wire.varint(service, 1)?.toInt() ?: continue
+            val id = serviceId(service) ?: continue
             val source = Wire.fields(Wire.bytes(service, 5) ?: continue)
             val f = Wire.fields(Wire.bytes(source, 2) ?: continue)
             return AudioService(
@@ -179,9 +192,7 @@ object ServiceDiscovery {
             val fields = Wire.fields(Wire.bytes(service, 6) ?: continue)
             val address = Wire.bytes(fields, 1)?.let { String(it, Charsets.UTF_8) } ?: continue
             // Packed as declared, though a car may send each method as its own varint.
-            val methods = fields.filter { it.number == 2 }.flatMap { f ->
-                f.bytes?.let(::packedVarints) ?: listOf(f.varint.toInt())
-            }
+            val methods = Wire.repeatedInts(fields, 2)
             return BluetoothService(id, address, methods)
         }
         return null
@@ -215,8 +226,8 @@ object ServiceDiscovery {
      *                         repeated TouchScreen touchscreen = 2; ... }
      *   TouchScreen { required int32 width = 1; required int32 height = 2; type = 3; }
      *
-     * Touch coordinates arrive in this space (1258x708 on the 2018 Uconnect) and must be
-     * scaled to the projected video size before injection. [keycodesSupported] is what the
+     * Touch reports use projected video coordinates; these dimensions describe the input
+     * hardware and help select a video configuration. [keycodesSupported] is what the
      * head unit says it will actually send over the Input channel as key events (steering-wheel
      * buttons, etc.) - not every unit reports the same set, so it's kept for diagnostics and to
      * know ahead of time whether a button like voice/PTT is even wired up on this hardware.
@@ -245,38 +256,18 @@ object ServiceDiscovery {
     private fun inputServices(response: ByteArray): List<InputService> = buildList {
         for (channel in Wire.allBytes(Wire.fields(response), 1)) {
             val service = Wire.fields(channel)
-            val id = Wire.varint(service, 1)?.toInt() ?: continue
+            val id = serviceId(service) ?: continue
             val input = Wire.bytes(service, 4) ?: continue
             val inputFields = Wire.fields(input)
             // A unit with only a knob and buttons has no touchscreen entry; it still has keys.
             val touchFields = Wire.bytes(inputFields, 2)?.let { Wire.fields(it) }.orEmpty()
             val width = Wire.varint(touchFields, 1)?.toInt() ?: 0
             val height = Wire.varint(touchFields, 2)?.toInt() ?: 0
-            // Declared packed, but some units send each keycode as its own field.
-            val keycodes = inputFields.filter { it.number == 1 }.flatMap { f ->
-                f.bytes?.let(::packedVarints) ?: listOf(f.varint.toInt())
-            }
+            val keycodes = Wire.repeatedInts(inputFields, 1)
             add(InputService(id, width, height, keycodes, Wire.varint(inputFields, 5)?.toInt() ?: 0))
         }
     }
 
-    /** Decodes a `[packed=true]` repeated varint field's raw bytes into individual values. */
-    private fun packedVarints(data: ByteArray): List<Int> = buildList {
-        var pos = 0
-        while (pos < data.size) {
-            var result = 0L
-            var shift = 0
-            while (pos < data.size) {
-                val b = data[pos].toInt() and 0xFF
-                result = result or ((b and 0x7F).toLong() shl shift)
-                pos++
-                if (b and 0x80 == 0) break
-                shift += 7
-            }
-            add(result.toInt())
-        }
-    }
-
     /**
      * The main screen's video sink. A head unit with a second screen, such as LIVI with a
      * cluster display, offers a sink for each; the one without a display id (0) is the main one.
@@ -289,7 +280,7 @@ object ServiceDiscovery {
     private fun videoServices(response: ByteArray): List<VideoService> = buildList {
         for (channel in Wire.allBytes(Wire.fields(response), 1)) {
             val service = Wire.fields(channel)
-            val id = Wire.varint(service, 1)?.toInt() ?: continue
+            val id = serviceId(service) ?: continue
             val sink = Wire.bytes(service, 3) ?: continue
 
             val sinkFields = Wire.fields(sink)
@@ -316,16 +307,15 @@ object ServiceDiscovery {
      *   SensorSourceService { repeated Sensor sensors = 1; }
      *   Sensor { required SensorType sensor_type = 1; }
      *
-     * Field numbers for what actually rides inside each SensorEvent once subscribed are not
-     * pinned down here - unlike video/audio/input, there's no independent source to check them
-     * against, so [CarSensors] shows the raw decode instead of trusting a guessed field map.
+     * SensorBatch contains repeated messages in fields 1 through 22 matching these type ids.
+     * The vehicle data screen keeps their raw contents for diagnostics.
      */
     class SensorService(val serviceId: Int, val types: List<Int>)
 
     fun findSensorService(response: ByteArray): SensorService? {
         for (channel in Wire.allBytes(Wire.fields(response), 1)) {
             val service = Wire.fields(channel)
-            val id = Wire.varint(service, 1)?.toInt() ?: continue
+            val id = serviceId(service) ?: continue
             val sensorSource = Wire.bytes(service, 2) ?: continue
             val types = Wire.allBytes(Wire.fields(sensorSource), 1).mapNotNull {
                 Wire.varint(Wire.fields(it), 1)?.toInt()

gearslip/src/main/java/app/seb3thehacker/gearslip/TlsSelfTest.kt

@@ -4,33 +4,25 @@ import java.net.Socket
 import java.nio.ByteBuffer
 import java.security.SecureRandom
 import java.security.cert.X509Certificate
+import javax.net.ssl.KeyManagerFactory
 import javax.net.ssl.SSLContext
 import javax.net.ssl.SSLEngine
 import javax.net.ssl.SSLEngineResult
 import javax.net.ssl.SSLEngineResult.HandshakeStatus
 import javax.net.ssl.X509ExtendedTrustManager
 
-/**
- * Runs [PhoneTls] against an in-process TLS client and checks that a full handshake plus a
- * data round trip works.
- *
- * This exists because of one specific hazard: a bug in the certificate, the key manager or
- * the engine wiring produces a dead connection in the car that is indistinguishable from a
- * head unit rejecting us - and the whole point of the spike is a trustworthy go/no-go
- * signal. Run this on the bench first; if it passes, a failure in the car is about the head
- * unit, not about this code.
- */
+/** Checks mutual TLS and an encrypted data round trip with an in-process head-unit peer. */
 object TlsSelfTest {
     private val log = GearslipLog.tagged("TLS")
 
-    fun run(identity: CertProvider.Identity): Boolean {
+    fun run(identity: CertProvider.Identity, withClientCertificate: Boolean = true): Boolean {
         log.i("=== TLS self-test starting ===")
         log.i("cert source: ${identity.source}")
         log.i("  subject = ${identity.certificate.subjectX500Principal}")
         log.i("  issuer  = ${identity.certificate.issuerX500Principal}")
         return try {
             val server = PhoneTls(identity.keyStore, identity.password)
-            val client = Driver(clientEngine())
+            val client = Driver(clientEngine(withClientCertificate))
 
             var outbound = client.pump(null) // ClientHello
             var rounds = 0
@@ -49,8 +41,7 @@ object TlsSelfTest {
                 return false
             }
 
-            // Data round trip, exercising the same encrypt path the spike uses for
-            // ServiceDiscoveryRequest.
+            // Exercise the same encrypt path used by ServiceDiscoveryRequest.
             val plaintext = "gearslip round trip".toByteArray()
             val decrypted = client.decrypt(server.encrypt(plaintext))
             if (!decrypted.contentEquals(plaintext)) {
@@ -66,9 +57,15 @@ object TlsSelfTest {
         }
     }
 
-    private fun clientEngine(): SSLEngine {
+    private fun clientEngine(withCertificate: Boolean): SSLEngine {
         val context = SSLContext.getInstance("TLSv1.2")
-        context.init(null, arrayOf(TrustAll()), SecureRandom())
+        val keyManagers = if (withCertificate) {
+            val client = SelfSignedCert.generate(commonName = "Self-test head unit")
+            KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm()).apply {
+                init(client.keyStore, SelfSignedCert.PASSWORD)
+            }.keyManagers
+        } else null
+        context.init(keyManagers, arrayOf(TrustAll()), SecureRandom())
         return context.createSSLEngine().apply {
             useClientMode = true
             enabledProtocols = arrayOf("TLSv1.2")

gearslip/src/main/java/app/seb3thehacker/gearslip/audio/AudioLink.kt

@@ -4,6 +4,8 @@ import app.seb3thehacker.gearslip.GearslipLog
 import app.seb3thehacker.gearslip.Protobuf
 import app.seb3thehacker.gearslip.ServiceDiscovery
 import app.seb3thehacker.gearslip.Wire
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
 
 /**
  * The phone end of the head unit's media audio sink, the audio twin of the video channel:
@@ -25,7 +27,10 @@ class AudioLink(
     /** Log name: "audio" for the media sink, "guidance" for the directions sink. */
     private val tag: String = "audio",
     private val sessionId: Int = SESSION_ID,
-    /** Media asks the car for focus; directions just start, and the car ducks music under them. */
+    /**
+     * Media asks the car for focus when it starts. Directions ask only around each announcement,
+     * through [askForSpeakers], and only when the music isn't already ours.
+     */
     private val asksFocus: Boolean = true,
     private val onReady: (AudioLink) -> Unit = { CarAudio.attach(it) },
     private val onClose: (AudioLink) -> Unit = { CarAudio.detach(it) },
@@ -58,6 +63,47 @@ class AudioLink(
 
     val channelId get() = service.serviceId
 
+    /** Sending audio now, which for media means the car has handed us the speakers. */
+    val streaming get() = started
+
+    @Volatile private var holdsSpeakers = false
+    @Volatile private var focusAnswer: CountDownLatch? = null
+    @Volatile private var answerDueBy = 0L
+
+    /** True just after [askForSpeakers] or [handBackSpeakers], when the car's next focus answer is ours. */
+    fun expectsFocusAnswer() = System.currentTimeMillis() < answerDueBy
+
+    /**
+     * For directions when nothing of ours is playing, so the car's speakers belong to the radio
+     * or a Bluetooth phone. Android Auto asks for them before each announcement, letting the
+     * other source duck, and hands them back afterwards. Speaking without asking left a 2025
+     * Nissan's Bosch head unit rebooting mid-drive (issue #35).
+     *
+     * Waits briefly for the car's answer and speaks anyway without one, as some cars never answer.
+     */
+    fun askForSpeakers() {
+        if (holdsSpeakers) return
+        val answer = CountDownLatch(1)
+        focusAnswer = answer
+        answerDueBy = System.currentTimeMillis() + FOCUS_WAIT_MS
+        holdsSpeakers = true
+        sendControl(MSG_FOCUS_REQUEST, Protobuf.varintField(1, FOCUS_GAIN_TRANSIENT_MAY_DUCK.toLong()))
+        GearslipLog.i("$tag: -> AudioFocusRequest(GAIN_TRANSIENT_MAY_DUCK)")
+        if (!answer.await(FOCUS_WAIT_MS, TimeUnit.MILLISECONDS)) {
+            GearslipLog.i("$tag: no focus answer after ${FOCUS_WAIT_MS}ms - speaking anyway")
+        }
+        focusAnswer = null
+    }
+
+    /** Gives back what [askForSpeakers] took, so the other source comes back to full volume. */
+    fun handBackSpeakers() {
+        if (!holdsSpeakers) return
+        holdsSpeakers = false
+        answerDueBy = System.currentTimeMillis() + FOCUS_WAIT_MS
+        runCatching { sendControl(MSG_FOCUS_REQUEST, Protobuf.varintField(1, FOCUS_RELEASE.toLong())) }
+        GearslipLog.i("$tag: -> AudioFocusRequest(RELEASE)")
+    }
+
     fun opened(status: Int) {
         GearslipLog.i("$tag: <- ChannelOpenResponse: status=$status")
         if (status != 0) {
@@ -161,6 +207,12 @@ class AudioLink(
     fun onFocus(state: Int) {
         val name = FOCUS_STATES[state] ?: "unknown($state)"
         GearslipLog.i("$tag: <- AudioFocusResponse state=$name")
+        if (!asksFocus) {
+            // Directions speak whatever the answer: a lost turn is worse than a loud one.
+            answerDueBy = 0L
+            focusAnswer?.countDown()
+            return
+        }
         val had = focusGranted
         focusGranted = state == FOCUS_STATE_GAIN || state == FOCUS_STATE_GAIN_TRANSIENT ||
             state == FOCUS_STATE_GAIN_MEDIA_ONLY
@@ -181,7 +233,19 @@ class AudioLink(
         startStream()
     }
 
+    /**
+     * Guards starting and stopping. [start] starts the stream at once for head units that never
+     * answer the focus request, and the car's answer arrives on another thread and starts it
+     * too: without this both got through, so the car got Start twice and two AAC encoders, and a
+     * 2014 head unit dropped the connection on the first audio.
+     */
+    private val startLock = Any()
+
     private fun startStream() {
+        synchronized(startLock) { startStreamLocked() }
+    }
+
+    private fun startStreamLocked() {
         if (!ready || started) return
         sendOnChannel(
             MSG_START,
@@ -200,6 +264,10 @@ class AudioLink(
     }
 
     override fun stop() {
+        synchronized(startLock) { stopLocked() }
+    }
+
+    private fun stopLocked() {
         if (!started) return
         started = false
         synchronized(ackLock) { ackLock.notifyAll() }
@@ -286,6 +354,7 @@ class AudioLink(
         configTimer?.interrupt()
         configTimer = null
         stop()
+        handBackSpeakers()
         ready = false
         onClose(this)
     }
@@ -303,7 +372,9 @@ class AudioLink(
         private const val MSG_SETUP_ANSWER = 255
         private const val STATUS_READY = 2
         private const val FOCUS_GAIN = 1
+        private const val FOCUS_GAIN_TRANSIENT_MAY_DUCK = 3
         private const val FOCUS_RELEASE = 4
+        private const val FOCUS_WAIT_MS = 500L
         private const val FOCUS_STATE_GAIN = 1
         private const val FOCUS_STATE_GAIN_TRANSIENT = 2
         private const val FOCUS_STATE_GAIN_MEDIA_ONLY = 6

gearslip/src/main/java/app/seb3thehacker/gearslip/audio/CarAudio.kt

@@ -44,6 +44,9 @@ object CarAudio {
 
     @Volatile private var link: Link? = null
 
+    /** Opens the car's media channel, left closed while music went over Bluetooth; null once open. */
+    @Volatile var openSink: (() -> Unit)? = null
+
     /** Rate and channel count the capture should use: the car's, or a sensible default. */
     val sampleRate get() = link?.sampleRate ?: 48_000
     val channels get() = link?.channels ?: 2
@@ -71,6 +74,7 @@ object CarAudio {
         when (_capture.value) {
             Capture.ON, Capture.ASKING, Capture.DENIED -> return
             Capture.OFF -> if (link == null) {
+                openSink?.invoke()
                 GearslipLog.i("audio: waiting for the car to offer an audio sink")
             } else {
                 ask()

gearslip/src/main/java/app/seb3thehacker/gearslip/call/CarCalls.kt

@@ -23,19 +23,19 @@ data class Caller(val number: String, val name: String?) {
 sealed interface CallUiState {
     data object None : CallUiState
     data class Ringing(val caller: Caller, val canDecline: Boolean) : CallUiState
-    data class Active(val caller: Caller?) : CallUiState
+    /** [since] is the uptime the call went off-hook, for the timer. */
+    data class Active(val caller: Caller?, val since: Long) : CallUiState
 }
 
 /**
- * Tracks the phone's call state for the car screen, and answers or declines through the two
+ * Tracks the phone's call state for the car screen, and answers or declines through the
  * doors a sideloaded app can use: [android.telecom.TelecomManager.acceptRingingCall] to answer,
- * and [GearslipCallScreening]'s response to decline one that is still ringing.
+ * [GearslipCallScreening]'s response to decline one that is still ringing, and
+ * [android.telecom.TelecomManager.endCall] to hang up, which needs only ANSWER_PHONE_CALLS for an
+ * ordinary carrier call. Mute is the phone's microphone mute, put back when the call ends.
  *
- * Ending a call already answered needs MODIFY_PHONE_STATE, a privileged permission Gearslip
- * cannot hold, so a call taken here is finished the way it would be without Gearslip at all -
- * from the phone itself, a paired headset, or the car's own Bluetooth if it has any. Call audio
- * stays on the phone's normal voice path too; nothing here sends it over the USB link, which
- * only ever carries media playback.
+ * Call audio stays on the phone's normal voice path; nothing here sends it over the USB link,
+ * which only ever carries media playback.
  */
 object CarCalls {
 
@@ -47,9 +47,14 @@ object CarCalls {
     private var pendingRespond: ((allow: Boolean) -> Unit)? = null
     private var ringingCaller: Caller? = null
 
+    private val _muted = MutableStateFlow(false)
+    val muted: StateFlow<Boolean> = _muted.asStateFlow()
+    private var audio: android.media.AudioManager? = null
+
     fun start(context: Context) {
         if (watcher != null) return
         if (context.checkSelfPermission(Manifest.permission.READ_PHONE_STATE) != PackageManager.PERMISSION_GRANTED) return
+        audio = context.getSystemService(android.media.AudioManager::class.java)
         val manager = context.getSystemService(TelephonyManager::class.java) ?: return
         val callback = object : TelephonyCallback(), TelephonyCallback.CallStateListener {
             override fun onCallStateChanged(state: Int) = onPhoneState(state)
@@ -66,6 +71,7 @@ object CarCalls {
         watcher = null
         pendingRespond = null
         ringingCaller = null
+        unmute()
         _state.value = CallUiState.None
     }
 
@@ -74,11 +80,15 @@ object CarCalls {
             TelephonyManager.CALL_STATE_IDLE -> {
                 pendingRespond = null
                 ringingCaller = null
+                // A mute left on would silence the microphone for everything after the call.
+                unmute()
                 _state.value = CallUiState.None
             }
             TelephonyManager.CALL_STATE_OFFHOOK -> {
                 pendingRespond = null
-                _state.value = CallUiState.Active(ringingCaller)
+                if (_state.value !is CallUiState.Active) {
+                    _state.value = CallUiState.Active(ringingCaller, android.os.SystemClock.uptimeMillis())
+                }
             }
             TelephonyManager.CALL_STATE_RINGING -> {
                 // The number itself only ever arrives through the screening service; if this
@@ -109,6 +119,39 @@ object CarCalls {
         runCatching { respond(false) }.onFailure { GearslipLog.w("calls: decline failed: ${it.message}") }
     }
 
+    /** A call Gearslip itself is placing, so the call pill can say who it's to. */
+    fun outgoingCall(context: Context, number: String) {
+        ringingCaller = Caller(number, lookUpName(context, number))
+    }
+
+    fun end(context: Context) {
+        if (context.checkSelfPermission(Manifest.permission.ANSWER_PHONE_CALLS) != PackageManager.PERMISSION_GRANTED) {
+            GearslipLog.w("calls: ending a call needs ANSWER_PHONE_CALLS, which was never granted")
+            return
+        }
+        val telecom = context.getSystemService(TelecomManager::class.java) ?: return
+        @Suppress("DEPRECATION")
+        runCatching { telecom.endCall() }
+            .onSuccess { if (!it) GearslipLog.w("calls: the phone wouldn't end the call") }
+            .onFailure { GearslipLog.w("calls: end failed: ${it.message}") }
+    }
+
+    fun toggleMute() {
+        val manager = audio ?: return
+        val want = !_muted.value
+        runCatching { manager.isMicrophoneMute = want }
+            .onFailure { GearslipLog.w("calls: mute failed: ${it.message}") }
+        // Read back rather than trusted: some phones let the call app overrule it.
+        _muted.value = manager.isMicrophoneMute
+        if (_muted.value != want) GearslipLog.w("calls: the phone didn't take the mute change")
+    }
+
+    private fun unmute() {
+        if (!_muted.value) return
+        runCatching { audio?.isMicrophoneMute = false }
+        _muted.value = false
+    }
+
     fun answer(context: Context) {
         if (context.checkSelfPermission(Manifest.permission.ANSWER_PHONE_CALLS) != PackageManager.PERMISSION_GRANTED) {
             GearslipLog.w("calls: answer needs ANSWER_PHONE_CALLS, which was never granted")

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CallOverlay.kt

@@ -33,21 +33,17 @@ import app.seb3thehacker.gearslip.call.CallUiState
 import app.seb3thehacker.gearslip.call.CarCalls
 
 /**
- * Sits above whatever the car is showing while a call is ringing or under way. Ringing takes the
- * whole screen, because nothing else matters more right now; an active call is a thin band along
- * the top, since from here the driver can only see who it is, not end it - see [CarCalls].
+ * Takes the whole car screen while a call is ringing, because nothing else matters more right
+ * now. A call under way moves into the nav bar instead (see NavCallPill), so it covers nothing.
  */
 @Composable
-fun CallOverlay(modifier: Modifier = Modifier) {
+fun CallOverlay() {
     val state by CarCalls.state.collectAsState()
     val context = LocalContext.current.applicationContext
 
     when (val s = state) {
-        // Covers the box regardless of where the caller aligned it, so the alignment below is
-        // only ever felt by the active-call banner, which is the one that isn't full-screen.
         is CallUiState.Ringing -> IncomingCall(s, onAnswer = { CarCalls.answer(context) }, onDecline = CarCalls::decline)
-        is CallUiState.Active -> ActiveCallBanner(s, modifier)
-        CallUiState.None -> {}
+        else -> {}
     }
 }
 
@@ -110,25 +106,3 @@ private fun CallButton(icon: ImageVector, label: String, color: Color, enabled:
         Text(label, style = MaterialTheme.typography.labelLarge)
     }
 }
-
-@Composable
-private fun ActiveCallBanner(s: CallUiState.Active, modifier: Modifier = Modifier) {
-    Surface(
-        color = MaterialTheme.colorScheme.primaryContainer,
-        contentColor = MaterialTheme.colorScheme.onPrimaryContainer,
-        modifier = modifier.fillMaxWidth(),
-    ) {
-        Row(
-            Modifier.padding(horizontal = 20.dp, vertical = 10.dp),
-            horizontalArrangement = Arrangement.Center,
-        ) {
-            Icon(Icons.Filled.Call, contentDescription = null, modifier = Modifier.size(20.dp))
-            Spacer(Modifier.height(0.dp))
-            Text(
-                "  On a call" + (s.caller?.let { " with ${it.label}" } ?: ""),
-                style = MaterialTheme.typography.labelLarge,
-                fontWeight = FontWeight.SemiBold,
-            )
-        }
-    }
-}

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarAppStage.kt

@@ -34,6 +34,8 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.layout.boundsInWindow
+import androidx.compose.ui.layout.onGloballyPositioned
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.viewinterop.AndroidView
@@ -59,13 +61,22 @@ fun CarAppStage(
 ) {
     val template by connection.template.collectAsStateWithLifecycle()
 
+    val cover = remember { ChromeCover() }
+    val navBar = LocalNavBarInset.current
+
     Box(Modifier.fillMaxSize()) {
         // The app's own drawing goes underneath; everything else is the host's rendering of
         // the template it described, laid over the top.
-        if (status.surfaceRequested) {
-            AppSurface(connection, frame, template, Modifier.fillMaxSize())
+        androidx.compose.runtime.CompositionLocalProvider(LocalChromeCover provides cover) {
+            if (status.surfaceRequested) {
+                AppSurface(connection, frame, template, Modifier.fillMaxSize())
+            }
+            TemplateChrome(
+                template,
+                Modifier.fillMaxSize().padding(top = if (embedded) 0.dp else CHROME_BAR, bottom = navBar),
+            )
+            BottomCover(navBar, Modifier.align(Alignment.BottomCenter))
         }
-        TemplateChrome(template, Modifier.fillMaxSize().padding(top = if (embedded) 0.dp else CHROME_BAR))
         if (!embedded) ChromeBar(status, onDisconnect, Modifier.align(Alignment.TopCenter))
     }
 }
@@ -84,13 +95,16 @@ private fun AppSurface(
     modifier: Modifier = Modifier,
 ) {
     var size by remember { mutableStateOf(0 to 0) }
+    var bounds by remember { mutableStateOf<androidx.compose.ui.geometry.Rect?>(null) }
+    val cover = LocalChromeCover.current
 
-    // The app lays its map out around whatever the host covers, so a template change moves the
-    // visible area even though the surface itself hasn't changed.
-    LaunchedEffect(template, size) {
-        val (width, height) = size
+    // The app lays its map out around whatever the host covers, so a template change or a card
+    // changing size moves the visible area even though the surface itself hasn't changed.
+    val (width, height) = size
+    val measured = bounds?.takeIf { width > 0 && height > 0 }?.let { cover?.visibleWithin(it, width, height) }
+    LaunchedEffect(template, size, measured) {
         if (width > 0 && height > 0) {
-            val visible = visibleAreaFor(template, width, height)
+            val visible = visibleAreaFor(template, width, height, measured)
             connection.reportAreas(visible = visible, stable = visible)
         }
     }
@@ -101,7 +115,9 @@ private fun AppSurface(
     // new one on it before releasing the old: the old display's disconnect then takes the new one's
     // connection with it and the map freezes for good. The nav bar hiding for the search keyboard
     // and the lyrics pane opening both resize this area.
-    androidx.compose.foundation.layout.BoxWithConstraints(modifier) {
+    androidx.compose.foundation.layout.BoxWithConstraints(
+        modifier.onGloballyPositioned { bounds = it.boundsInWindow() },
+    ) {
         val epoch by connection.surfaceEpoch.collectAsState()
         androidx.compose.runtime.key(constraints.maxWidth, constraints.maxHeight, epoch) {
             SurfaceHost(connection, frame, onSize = { size = it }, Modifier.fillMaxSize())

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarFullscreen.kt

@@ -0,0 +1,51 @@
+package app.seb3thehacker.gearslip.car
+
+import android.os.SystemClock
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+
+/**
+ * Full screen for the screen that asks for it (the browser, or a video in it): no header and no
+ * nav bar. A swipe in from the top or bottom edge brings the nav bar back for a few seconds,
+ * with a button to leave full screen; [revealed] says when.
+ */
+object CarFullscreen {
+
+    var active by mutableStateOf(false)
+        private set
+
+    var revealed by mutableStateOf(false)
+        private set
+
+    private var lastTouch = 0L
+
+    fun enter() {
+        active = true
+        revealed = false
+    }
+
+    fun exit() {
+        active = false
+        revealed = false
+    }
+
+    /** A swipe in from an edge: show the nav bar and the way out. */
+    fun reveal() {
+        if (!active) return
+        lastTouch = SystemClock.uptimeMillis()
+        revealed = true
+    }
+
+    /** Any touch keeps a revealed bar up, so it doesn't slide away under a finger reaching for it. */
+    fun touch() {
+        if (revealed) lastTouch = SystemClock.uptimeMillis()
+    }
+
+    /** Called on a timer; hides the bar again after [REVEAL_MS] without a touch. */
+    fun tick() {
+        if (revealed && SystemClock.uptimeMillis() - lastTouch >= REVEAL_MS) revealed = false
+    }
+
+    private const val REVEAL_MS = 4_000L
+}

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarHomeScreen.kt

@@ -94,12 +94,8 @@ fun CarHome() {
     }
     val splitScreen = phase == CarMedia.Phase.READY && now.isActive && panel != SidePanel.NONE
 
-    // No outer padding on any side, split screen or not - only the gap between the two panes
-    // when the player is sharing the screen with the map.
-    Row(
-        Modifier.fillMaxSize(),
-        horizontalArrangement = Arrangement.spacedBy(8.dp),
-    ) {
+    // No padding anywhere, split screen or not: the player sits flush against the map.
+    Row(Modifier.fillMaxSize()) {
         Box(
             Modifier
                 .weight(if (splitScreen) 2.1f else 1f)
@@ -108,7 +104,7 @@ fun CarHome() {
             MapPane(navStatus, frame)
         }
         if (splitScreen) {
-            val side = Modifier.weight(1f).fillMaxHeight()
+            val side = Modifier.weight(1f).fillMaxHeight().padding(bottom = LocalNavBarInset.current)
             if (panel == SidePanel.LYRICS) SideLyrics(now, side) else DockedPlayer(now, side)
         }
     }

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarKeyboard.kt

@@ -44,6 +44,12 @@ object CarKeyboardVisibility {
     val state = mutableStateOf(false)
 }
 
+/**
+ * True for the car UI the phone's own car preview draws. The phone is in hand there, so a
+ * [CarKeyboard] draws nothing and the phone's keyboard does the typing instead (see [PhoneTyping]).
+ */
+val LocalCarPreview = compositionLocalOf { false }
+
 /**
  * A keyboard the host draws itself.
  *
@@ -73,10 +79,11 @@ fun CarKeyboard(
 ) {
     var symbols by remember { mutableStateOf(false) }
     var shifted by remember { mutableStateOf(false) }
+    val preview = LocalCarPreview.current
 
-    DisposableEffect(Unit) {
-        CarKeyboardVisibility.state.value = true
-        onDispose { CarKeyboardVisibility.state.value = false }
+    DisposableEffect(preview) {
+        if (!preview) CarKeyboardVisibility.state.value = true
+        onDispose { if (!preview) CarKeyboardVisibility.state.value = false }
     }
 
     // The same field on the phone, for typing on its own keyboard: see [PhoneTyping].
@@ -88,6 +95,7 @@ fun CarKeyboard(
     }
     DisposableEffect(phoneField) { onDispose { PhoneTyping.close(phoneField) } }
     LaunchedEffect(text) { PhoneTyping.carText(phoneField, text) }
+    if (preview) return
 
     val rows = if (symbols) SYMBOL_ROWS else LETTER_ROWS
     val keyHeight = keyHeight(LocalConfiguration.current.screenHeightDp)

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarSensors.kt

@@ -5,16 +5,7 @@ import app.seb3thehacker.gearslip.Wire
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 
-/**
- * Everything the head unit's sensor channel has offered and sent, for the "Vehicle data" screen.
- *
- * [ServiceDiscovery.findSensorService] tells us which numeric sensor types this head unit is
- * willing to stream; [SensorType] names the ones publicly documented by other AA reverse-engineering
- * projects (aasdk, openauto). That mapping is carried over from other projects, not verified
- * against this exact unit, so it's a label, not a guarantee - the raw field dump next to it is
- * the ground truth. Once [onEvent] starts decoding real traffic from the 2018 Uconnect, correct
- * any type that turns out to be mislabeled.
- */
+/** Raw sensor readings, keyed by SensorBatch field number, which matches the sensor type id. */
 object CarSensors {
 
     data class Reading(val typeId: Int, val typeName: String, val raw: String, val updatedAtMs: Long)
@@ -30,16 +21,10 @@ object CarSensors {
         }
     }
 
-    /**
-     * One SensorEventIndication. Every reverse-engineered version of this message multiplexes
-     * every sensor type into one shared set of message-level field numbers (field N = "the data
-     * for sensor type N", roughly) rather than tagging events with the type id from
-     * SensorType.type - so field number is read here as a best-effort type id, same as the
-     * other services in this file.
-     */
+    /** Each SensorBatch field contains repeated readings of one sensor type. */
     fun onEvent(body: ByteArray) {
         val now = System.currentTimeMillis()
-        val fields = Wire.fields(body)
+        val fields = Wire.fields(body).filter { it.wireType == 2 }
         val byType = fields.groupBy { it.number }
         val updated = byType.mapValues { (number, group) ->
             Reading(
@@ -61,10 +46,7 @@ object CarSensors {
     }
 }
 
-/**
- * Sensor type ids as named across public Android Auto reverse-engineering references. Treated as
- * a label, not a fact - see [CarSensors] doc.
- */
+/** Sensor type values shared by the discovery service and SensorBatch. */
 object SensorType {
     private val NAMES = mapOf(
         1 to "Location (GPS)",
@@ -89,6 +71,10 @@ object SensorType {
         20 to "Gyroscope",
         21 to "GPS satellites",
         22 to "Toll card",
+        23 to "Vehicle energy model",
+        24 to "Trailer",
+        25 to "Raw vehicle energy model",
+        26 to "Raw EV trip settings",
     )
 
     fun name(id: Int): String = NAMES[id]?.let { "$it (#$id)" } ?: "Sensor #$id"

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarSettings.kt

@@ -18,6 +18,33 @@ enum class Units { AUTO, IMPERIAL, METRIC }
 /** The car UI's own colours. Separate from [NightMode], which is about the light outside (the map). */
 enum class AppTheme { PHONE, LIGHT, DARK }
 
+/** A screen's width and height in pixels, as someone typed it: "1280x480". */
+data class ScreenSize(val width: Int, val height: Int) {
+    override fun toString() = "${width}x$height"
+
+    companion object {
+        fun parse(text: String?): ScreenSize? {
+            val parts = text?.lowercase()?.split('x', '×', ' ')?.filter { it.isNotBlank() } ?: return null
+            if (parts.size != 2) return null
+            val w = parts[0].trim().toIntOrNull() ?: return null
+            val h = parts[1].trim().toIntOrNull() ?: return null
+            return if (w in 100..8000 && h in 100..8000) ScreenSize(w, h) else null
+        }
+    }
+}
+
+/**
+ * How a head unit puts our frame on a screen of another shape. [CROP] cuts the edges off, as
+ * a car's own margins do; [SQUASH] shrinks the whole frame to fit, stretching everything.
+ */
+enum class ScreenFit { CROP, SQUASH }
+
+/** What size the phone's car preview draws: the last car's, this device's whole screen, or one typed in. */
+enum class PreviewSize { LAST_CAR, FILL, CUSTOM }
+
+/** When the nav bar gets out of the way: never, during a route, or whenever the map is up. */
+enum class NavBarMode { SHOW, HIDE_NAVIGATING, HIDE }
+
 /**
  * Settings changed from the car screen itself. Held as flows so the car UI reacts the moment a
  * button is tapped, and persisted through [AppSettings] so they survive the next connection.
@@ -45,6 +72,11 @@ private const val KEY_LOCATION_WARNING = "car_location_warning"
     private const val KEY_CAR_SENSORS = "car_sensors_enabled"
     private const val KEY_SEEN_SAFETY_WARNING = "car_seen_safety_warning"
     private const val KEY_UNITS = "car_units"
+    private const val KEY_NAV_BAR = "car_nav_bar"
+    private const val KEY_SCREEN_SIZE = "car_screen_size"
+    private const val KEY_SCREEN_FIT = "car_screen_fit"
+    private const val KEY_PREVIEW_SIZE = "preview_size"
+    private const val KEY_PREVIEW_CUSTOM = "preview_custom_size"
     private const val KEY_WHATS_NEW = "car_whats_new_after_updates"
     private const val KEY_WHATS_NEW_SEEN = "car_whats_new_seen_code"
 
@@ -84,6 +116,43 @@ private const val KEY_LOCATION_WARNING = "car_location_warning"
 
     val units: StateFlow<Units> = unitsFlow
 
+    private val screenSizeFlow = MutableStateFlow<ScreenSize?>(null)
+    private val screenFitFlow = MutableStateFlow(ScreenFit.CROP)
+    private val previewSizeFlow = MutableStateFlow(PreviewSize.LAST_CAR)
+    private val previewCustomFlow = MutableStateFlow<ScreenSize?>(null)
+
+    /** The car screen's real size, when the head unit gets it wrong; null trusts the head unit. */
+    val screenSize: StateFlow<ScreenSize?> = screenSizeFlow
+    val screenFit: StateFlow<ScreenFit> = screenFitFlow
+    val previewSize: StateFlow<PreviewSize> = previewSizeFlow
+    val previewCustom: StateFlow<ScreenSize?> = previewCustomFlow
+
+    /** Takes effect the next time the car connects: the video size is agreed at the start. */
+    fun setScreenSize(size: ScreenSize?) {
+        screenSizeFlow.value = size
+        AppSettings.putString(app, KEY_SCREEN_SIZE, size?.toString().orEmpty())
+    }
+
+    fun setScreenFit(fit: ScreenFit) {
+        screenFitFlow.value = fit
+        AppSettings.putString(app, KEY_SCREEN_FIT, fit.name)
+    }
+
+    fun setPreviewSize(size: PreviewSize, custom: ScreenSize? = previewCustomFlow.value) {
+        previewSizeFlow.value = size
+        previewCustomFlow.value = custom
+        AppSettings.putString(app, KEY_PREVIEW_SIZE, size.name)
+        AppSettings.putString(app, KEY_PREVIEW_CUSTOM, custom?.toString().orEmpty())
+    }
+
+    private val navBarFlow = MutableStateFlow(NavBarMode.SHOW)
+    val navBarMode: StateFlow<NavBarMode> = navBarFlow
+
+    fun setNavBarMode(mode: NavBarMode) {
+        navBarFlow.value = mode
+        AppSettings.putString(app, KEY_NAV_BAR, mode.name)
+    }
+
 
     private val whatsNewFlow = MutableStateFlow(true)
     private val whatsNewSeenFlow = MutableStateFlow(0)
@@ -243,6 +312,17 @@ private const val KEY_LOCATION_WARNING = "car_location_warning"
         unitsFlow.value = runCatching {
             Units.valueOf(AppSettings.getString(app, KEY_UNITS, Units.AUTO.name))
         }.getOrDefault(Units.AUTO)
+        screenSizeFlow.value = ScreenSize.parse(AppSettings.getString(app, KEY_SCREEN_SIZE, ""))
+        screenFitFlow.value = runCatching {
+            ScreenFit.valueOf(AppSettings.getString(app, KEY_SCREEN_FIT, ScreenFit.CROP.name))
+        }.getOrDefault(ScreenFit.CROP)
+        previewSizeFlow.value = runCatching {
+            PreviewSize.valueOf(AppSettings.getString(app, KEY_PREVIEW_SIZE, PreviewSize.LAST_CAR.name))
+        }.getOrDefault(PreviewSize.LAST_CAR)
+        previewCustomFlow.value = ScreenSize.parse(AppSettings.getString(app, KEY_PREVIEW_CUSTOM, ""))
+        navBarFlow.value = runCatching {
+            NavBarMode.valueOf(AppSettings.getString(app, KEY_NAV_BAR, NavBarMode.SHOW.name))
+        }.getOrDefault(NavBarMode.SHOW)
         whatsNewFlow.value = AppSettings.getString(app, KEY_WHATS_NEW, "true") == "true"
         whatsNewSeenFlow.value = AppSettings.getString(app, KEY_WHATS_NEW_SEEN, "0").toIntOrNull() ?: 0
     }

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarSettingsScreen.kt

@@ -5,6 +5,8 @@ import app.seb3thehacker.gearslip.car.theme.*
 import android.os.Build
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
@@ -51,6 +53,9 @@ fun CarSettingsScreen() {
     val open by CarSettings.openOnConnect.collectAsState()
     val night by CarSettings.nightMode.collectAsState()
     val units by CarSettings.units.collectAsState()
+    val navBar by CarSettings.navBarMode.collectAsState()
+    val screenSize by CarSettings.screenSize.collectAsState()
+    val screenFit by CarSettings.screenFit.collectAsState()
     val whatsNew by CarSettings.whatsNewAfterUpdates.collectAsState()
     val pipeAudio by CarSettings.pipeAudio.collectAsState()
     val speakDirections by CarSettings.speakDirections.collectAsState()
@@ -70,140 +75,215 @@ fun CarSettingsScreen() {
         value = withContext(Dispatchers.Default) { CertSummary.read(context) }
     }
 
-    Column(
-        Modifier
-            .fillMaxSize()
-            .verticalScroll(rememberScrollState())
-            .padding(horizontal = 24.dp, vertical = 16.dp),
+    LazyColumn(
+        Modifier.fillMaxSize(),
+        // Built as it scrolls into view rather than all at once: every row here is a set of
+        // buttons, and building the whole screen made opening Settings visibly slow.
+        contentPadding = PaddingValues(horizontal = 24.dp, vertical = 16.dp),
         verticalArrangement = Arrangement.spacedBy(20.dp),
     ) {
-        ScreenHeader("Settings")
+        item {
+            ScreenHeader("Settings")
+        }
 
-        ChoiceRow(
-            "Open on connect",
-            listOf(CarSettings.HOME to "Home") + CarApps.all.filter { it.id != "settings" }.map { it.id to it.label },
-            open,
-        ) { CarSettings.setOpenOnConnect(it) }
+        item {
+            ChoiceRow(
+                "Open on connect",
+                listOf(CarSettings.HOME to "Home") + CarApps.all.filter { it.id != "settings" }.map { it.id to it.label },
+                open,
+            ) { CarSettings.setOpenOnConnect(it) }
+        }
 
-        ChoiceRow(
-            "Size",
-            listOf(1f to "Normal", 1.25f to "Large", 1.5f to "Extra large"),
-            scale,
-        ) { CarSettings.setScale(it) }
+        item {
+            ChoiceRow(
+                "Size",
+                listOf(1f to "Normal", 1.25f to "Large", 1.5f to "Extra large"),
+                scale,
+            ) { CarSettings.setScale(it) }
+        }
 
-        ChoiceRow(
-            "App theme",
-            listOf(AppTheme.PHONE to "Follow phone", AppTheme.LIGHT to "Light", AppTheme.DARK to "Dark"),
-            theme,
-        ) { CarSettings.setAppTheme(it) }
+        item {
+            ChoiceRow(
+                "App theme",
+                listOf(AppTheme.PHONE to "Follow phone", AppTheme.LIGHT to "Light", AppTheme.DARK to "Dark"),
+                theme,
+            ) { CarSettings.setAppTheme(it) }
+        }
 
-        ChoiceRow(
-            "Theme",
-            GsThemes.builtIn.map { it.id to it.name },
-            uiTheme,
-        ) { CarSettings.setUiTheme(it) }
+        item {
+            ChoiceRow(
+                "Theme",
+                GsThemes.builtIn.map { it.id to it.name },
+                uiTheme,
+            ) { CarSettings.setUiTheme(it) }
+        }
 
-        ChoiceRow(
-            "Map day/night",
-            listOf(NightMode.AUTO to "Auto", NightMode.DAY to "Day", NightMode.NIGHT to "Night"),
-            night,
-        ) { CarSettings.setNightMode(it) }
+        item {
+            ChoiceRow(
+                "Map day/night",
+                listOf(NightMode.AUTO to "Auto", NightMode.DAY to "Day", NightMode.NIGHT to "Night"),
+                night,
+            ) { CarSettings.setNightMode(it) }
+        }
 
-        ChoiceRow(
-            "Units",
-            listOf(Units.AUTO to "Auto", Units.IMPERIAL to "Imperial (mi, ft, °F)", Units.METRIC to "Metric (km, m, °C)"),
-            units,
-        ) { CarSettings.setUnits(it) }
+        item {
+            ChoiceRow(
+                "Units",
+                listOf(Units.AUTO to "Auto", Units.IMPERIAL to "Imperial (mi, ft, °F)", Units.METRIC to "Metric (km, m, °C)"),
+                units,
+            ) { CarSettings.setUnits(it) }
+        }
 
-        ChoiceRow(
-            "Player in the nav bar",
-            listOf(false to "Skip buttons", true to "Song title"),
-            playerTitle,
-        ) { CarSettings.setPlayerTitle(it) }
+        // For a head unit that reports the wrong size and stretches the picture (issue #12).
+        item {
+            ChoiceRow(
+                "Screen size (next connection)",
+                listOf<ScreenSize?>(null).plus(SCREEN_PRESETS).plus(screenSize).distinct()
+                    .map { it to (it?.toString() ?: "From the car") },
+                screenSize,
+            ) { CarSettings.setScreenSize(it) }
+        }
 
-        ChoiceRow(
-            "Autoplay on connect",
-            listOf(false to "Off", true to "On"),
-            autoplay,
-        ) { CarSettings.setAutoplay(it) }
+        if (screenSize != null) item {
+            ChoiceRow(
+                "Fit to the screen",
+                listOf(ScreenFit.CROP to "Crop the edges", ScreenFit.SQUASH to "Squash to fit"),
+                screenFit,
+            ) { CarSettings.setScreenFit(it) }
+        }
 
-        ChoiceRow(
-            "Car audio",
-            listOf(false to "Bluetooth", true to "USB"),
-            pipeAudio,
-        ) { CarSettings.setPipeAudio(it) }
-        Text(
-            "USB sends the phone's sound through Gearslip. Android asks to share your screen each " +
-                "drive, and a few apps block it. Bluetooth plays as the phone normally would, and " +
-                "Android never asks.",
-            style = MaterialTheme.typography.bodySmall,
-            color = MaterialTheme.colorScheme.onSurfaceVariant,
-        )
-        if (!pipeAudio) {
+        item {
+            ChoiceRow(
+                "Nav bar",
+                listOf(
+                    NavBarMode.SHOW to "Always show",
+                    NavBarMode.HIDE_NAVIGATING to "Hide while navigating",
+                    NavBarMode.HIDE to "Hide until tapped",
+                ),
+                navBar,
+            ) { CarSettings.setNavBarMode(it) }
+        }
+
+        item {
+            ChoiceRow(
+                "Player in the nav bar",
+                listOf(false to "Skip buttons", true to "Song title"),
+                playerTitle,
+            ) { CarSettings.setPlayerTitle(it) }
+        }
+
+        item {
+            ChoiceRow(
+                "Autoplay on connect",
+                listOf(false to "Off", true to "On"),
+                autoplay,
+            ) { CarSettings.setAutoplay(it) }
+        }
+
+        item {
+            ChoiceRow(
+                "Car audio",
+                listOf(false to "Bluetooth", true to "USB"),
+                pipeAudio,
+            ) { CarSettings.setPipeAudio(it) }
+        }
+
+        item {
+            Text(
+                "USB sends the phone's sound through Gearslip. Android asks to share your screen each " +
+                    "drive, and a few apps block it. Bluetooth plays as the phone normally would, and " +
+                    "Android never asks.",
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+
+        if (!pipeAudio) item {
             ChoiceRow(
                 "Warn when Bluetooth isn't connected",
                 listOf(false to "Off", true to "On"),
                 bluetoothWarning,
             ) { CarSettings.setBluetoothWarning(it) }
         }
-        ChoiceRow(
-            "Warn when location is off",
-            listOf(false to "Off", true to "On"),
-            locationWarning,
-        ) { CarSettings.setLocationWarning(it) }
 
-        ChoiceRow(
-            "Spoken directions",
-            listOf(false to "Off", true to "On"),
-            speakDirections,
-        ) { CarSettings.setSpeakDirections(it) }
-        Text(
-            "Gearslip reads each turn aloud through the car's speakers, and the music dips while it " +
-                "speaks. Turn it off if your map app's own voice already plays in the car.",
-            style = MaterialTheme.typography.bodySmall,
-            color = MaterialTheme.colorScheme.onSurfaceVariant,
-        )
+        item {
+            ChoiceRow(
+                "Warn when location is off",
+                listOf(false to "Off", true to "On"),
+                locationWarning,
+            ) { CarSettings.setLocationWarning(it) }
+        }
 
-        ExperimentalFeatureRow(
-            title = "Use the phone's speech recognition",
-            description = "Listens through the phone's own speech service instead of Gearslip's. On " +
-                "most phones that's Google's, which may send your voice to Google. GrapheneOS has " +
-                "none, so Gearslip keeps using its own.",
-            checked = systemSpeech,
-        ) { CarSettings.setSystemSpeech(it) }
+        item {
+            ChoiceRow(
+                "Spoken directions",
+                listOf(false to "Off", true to "On"),
+                speakDirections,
+            ) { CarSettings.setSpeakDirections(it) }
+        }
 
-        WebPageSetting()
+        item {
+            Text(
+                "Gearslip reads each turn aloud through the car's speakers, and the music dips while it " +
+                    "speaks. Turn it off if your map app's own voice already plays in the car.",
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
 
-        ScreenFit(vehicle)
+        item {
+            ExperimentalFeatureRow(
+                title = "Use the phone's speech recognition",
+                description = "Listens through the phone's own speech service instead of Gearslip's. On " +
+                    "most phones that's Google's, which may send your voice to Google. GrapheneOS has " +
+                    "none, so Gearslip keeps using its own.",
+                checked = systemSpeech,
+            ) { CarSettings.setSystemSpeech(it) }
+        }
 
-        ChoiceRow(
-            "Experimental features",
-            listOf(false to "Hide", true to "Show"),
-            experimentalFeatures,
-        ) { CarSettings.setExperimentalFeaturesEnabled(it) }
-        if (experimentalFeatures) {
+        item {
+            WebPageSetting()
+        }
+
+        item {
+            ScreenFit(vehicle)
+        }
+
+        item {
+            ChoiceRow(
+                "Experimental features",
+                listOf(false to "Hide", true to "Show"),
+                experimentalFeatures,
+            ) { CarSettings.setExperimentalFeaturesEnabled(it) }
+        }
+
+        if (experimentalFeatures) item {
             ExperimentalFeaturesList(carSensors)
         }
 
-        Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-            Text("Connection", style = MaterialTheme.typography.titleMedium, color = MaterialTheme.colorScheme.primary)
-            Info("Phone", "${Build.MANUFACTURER} ${Build.MODEL}")
-            Info("Vehicle", vehicle.ifEmpty { "-" })
-            Info("Video", display.ifEmpty { "-" })
-            Info("Certificate", cert?.headline ?: "Checking…")
+        item {
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                Text("Connection", style = MaterialTheme.typography.titleMedium, color = MaterialTheme.colorScheme.primary)
+                Info("Phone", "${Build.MANUFACTURER} ${Build.MODEL}")
+                Info("Vehicle", vehicle.ifEmpty { "-" })
+                Info("Video", display.ifEmpty { "-" })
+                Info("Certificate", cert?.headline ?: "Checking…")
+            }
         }
 
-        Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
-            Text("About", style = MaterialTheme.typography.titleMedium, color = MaterialTheme.colorScheme.primary)
-            Info("Version", app.seb3thehacker.gearslip.BuildConfig.VERSION_NAME)
-            Info("Build", app.seb3thehacker.gearslip.BuildConfig.VERSION_CODE.toString())
-            ExperimentalFeatureRow(
-                "What's new after updates",
-                "Show the list of changes once, the first time the car connects after an update.",
-                whatsNew,
-            ) { CarSettings.setWhatsNewAfterUpdates(it) }
-            GsButton(onClick = CarSettings::openWhatsNew, tone = GsTone.Tonal, modifier = Modifier.height(56.dp)) {
-                Text("What's new", style = MaterialTheme.typography.titleMedium)
+        item {
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                Text("About", style = MaterialTheme.typography.titleMedium, color = MaterialTheme.colorScheme.primary)
+                Info("Version", app.seb3thehacker.gearslip.BuildConfig.VERSION_NAME)
+                Info("Build", app.seb3thehacker.gearslip.BuildConfig.VERSION_CODE.toString())
+                ExperimentalFeatureRow(
+                    "What's new after updates",
+                    "Show the list of changes once, the first time the car connects after an update.",
+                    whatsNew,
+                ) { CarSettings.setWhatsNewAfterUpdates(it) }
+                GsButton(onClick = CarSettings::openWhatsNew, tone = GsTone.Tonal, modifier = Modifier.height(56.dp)) {
+                    Text("What's new", style = MaterialTheme.typography.titleMedium)
+                }
             }
         }
     }
@@ -406,3 +486,8 @@ private fun StepButton(text: String, modifier: Modifier, onClick: () -> Unit) {
     }
 }
 
+/** Common car screen sizes; Settings on the phone takes any other. */
+private val SCREEN_PRESETS = listOf(
+    ScreenSize(800, 480), ScreenSize(1024, 600), ScreenSize(1280, 480), ScreenSize(1280, 720),
+    ScreenSize(1440, 540), ScreenSize(1920, 720), ScreenSize(1920, 1080),
+)

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarUi.kt

@@ -1,5 +1,8 @@
 package app.seb3thehacker.gearslip.car
 
+import androidx.compose.material.icons.filled.Call
+import app.seb3thehacker.gearslip.call.CarCalls
+import app.seb3thehacker.gearslip.call.CallUiState
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.LocalIndication
@@ -123,6 +126,7 @@ fun CarUi() {
         while (true) {
             delay(250)
             controlsWake.tick()
+            CarFullscreen.tick()
         }
     }
     // The knob counts as a touch: the map's buttons can't be found while they're faded out.
@@ -193,10 +197,25 @@ fun CarUi() {
                     .fillMaxSize()
                     // Watches every touch without taking any: first in line, consumes nothing.
                     .pointerInput(controlsWake) {
+                        // In full screen, a swipe that starts at the top or bottom edge brings the
+                        // nav bar back. Only from the very edge, so scrolling a page still scrolls.
+                        val edge = 32.dp.toPx()
+                        val slop = 24.dp.toPx()
+                        var startY = -1f
                         awaitPointerEventScope {
                             while (true) {
-                                awaitPointerEvent(PointerEventPass.Initial)
+                                val event = awaitPointerEvent(PointerEventPass.Initial)
                                 controlsWake.touch()
+                                CarFullscreen.touch()
+                                val change = event.changes.firstOrNull() ?: continue
+                                if (!CarFullscreen.active) continue
+                                if (change.pressed && !change.previousPressed) {
+                                    val y = change.position.y
+                                    startY = if (y < edge || y > size.height - edge) y else -1f
+                                } else if (startY >= 0f && change.pressed && kotlin.math.abs(change.position.y - startY) > slop) {
+                                    CarFullscreen.reveal()
+                                    startY = -1f
+                                }
                             }
                         }
                     },
@@ -211,6 +230,26 @@ fun CarUi() {
                 }
                 val screen = navigator.current
                 val safetyWarningSeen by CarSettings.hasSeenSafetyWarning.collectAsState()
+                val keyboardVisible by CarKeyboardVisibility.state
+                // Off "Always show", the bar floats over the map rather than taking a row of its
+                // own: hiding it then leaves the map's surface the size it was. Resizing it would
+                // hand the map app a new surface each time, and some go black on that.
+                val navBarMode by CarSettings.navBarMode.collectAsState()
+                val appTemplate by CarServices.nav.template.collectAsState()
+                val floatingBar = navBarMode != NavBarMode.SHOW
+                val barMayHide = screen == CarScreen.Home && when (navBarMode) {
+                    NavBarMode.SHOW -> false
+                    NavBarMode.HIDE_NAVIGATING -> appTemplate is androidx.car.app.navigation.model.NavigationTemplate
+                    NavBarMode.HIDE -> true
+                }
+                // A full wait from when hiding becomes possible, not from whenever the last touch was.
+                LaunchedEffect(barMayHide) { if (barMayHide) controlsWake.touch() }
+                // A call keeps the bar up whatever the setting: End and Mute live on it.
+                val onCall = CarCalls.state.collectAsState().value is CallUiState.Active
+                val barShown = !keyboardVisible && (!barMayHide || controlsWake.navBarAwake || onCall)
+                val homeInset = if (floatingBar && barShown) NAV_BAR_HEIGHT else 0.dp
+                // Only the screen that asked: going Home or anywhere else ends it.
+                val fullscreen = CarFullscreen.active && screen != CarScreen.Home
                 Box(Modifier.fillMaxSize().padding(pad)) {
                 Column(Modifier.fillMaxSize()) {
                     if (!safetyWarningSeen) {
@@ -223,12 +262,29 @@ fun CarUi() {
                         // Home never leaves the composition; other screens cover it. Dropping it
                         // would tear down the map's surface, and coming back would then show black
                         // while the nav app redrew on a new one.
-                        CarHome()
+                        CompositionLocalProvider(LocalNavBarInset provides homeInset) { CarHome() }
+                    }
+                    // The keyboard takes the nav bar's row instead of squeezing in above it -
+                    // nothing on the nav bar is useful mid-type, and the screen is too small to
+                    // show both.
+                    if (!floatingBar && !keyboardVisible) CarNavBar(navigator)
+                }
+                // Every other screen, and everything that pops up, in a layer over Home rather
+                // than inside its area: full screen grows this layer over the nav bar's row while
+                // Home, and the map's surface in it, keeps its size.
+                if (safetyWarningSeen) {
+                    Box(
+                        Modifier
+                            .fillMaxSize()
+                            .padding(bottom = if (!floatingBar && !keyboardVisible && !fullscreen) NAV_BAR_HEIGHT else 0.dp),
+                    ) {
                         if (screen != CarScreen.Home) {
                             Box(
                                 Modifier
                                     .fillMaxSize()
                                     .background(MaterialTheme.colorScheme.background)
+                                    // The floating bar never hides here, so keep the screen clear of it.
+                                    .padding(bottom = if (floatingBar && !keyboardVisible && !fullscreen) NAV_BAR_HEIGHT else 0.dp)
                                     // Keeps touches that miss this screen's controls off the map.
                                     .pointerInput(Unit) { detectTapGestures { } },
                             ) {
@@ -247,7 +303,7 @@ fun CarUi() {
                                 }
                             }
                         }
-                        CarToastOverlay(Modifier.align(Alignment.BottomCenter))
+                        CarToastOverlay(Modifier.align(Alignment.BottomCenter).padding(bottom = homeInset))
                         CallPromptOverlay()
                         BluetoothPairOverlay()
                         PopupTimer()
@@ -258,21 +314,38 @@ fun CarUi() {
                         )
                         // Above the popup: a call is more urgent than any notification.
                         VoiceHelpOverlay(Modifier.align(Alignment.Center))
-                        CallOverlay(Modifier.align(Alignment.TopCenter))
-                        AssistantOverlay(Modifier.align(Alignment.BottomCenter))
+                        CallOverlay()
+                        AssistantOverlay(Modifier.align(Alignment.BottomCenter).padding(bottom = homeInset))
                         if (app.seb3thehacker.gearslip.BuildConfig.DEBUG) {
                             // Bottom corner, not top: a screen's own header almost always puts
                             // something in the top-right (settings, search, a Liked Songs
                             // shortcut) and this badge used to sit right on top of it, hiding
                             // whatever the screen drew there.
-                            DebugBuildBadge(Modifier.align(Alignment.BottomEnd))
+                            DebugBuildBadge(Modifier.align(Alignment.BottomEnd).padding(bottom = homeInset))
+                        }
+                        if (floatingBar || fullscreen) {
+                            androidx.compose.animation.AnimatedVisibility(
+                                if (fullscreen) CarFullscreen.revealed || onCall else barShown,
+                                Modifier.align(Alignment.BottomCenter),
+                                enter = androidx.compose.animation.slideInVertically { it },
+                                exit = androidx.compose.animation.slideOutVertically { it },
+                            ) { CarNavBar(navigator) }
+                        }
+                        if (fullscreen) {
+                            androidx.compose.animation.AnimatedVisibility(
+                                CarFullscreen.revealed,
+                                Modifier.align(Alignment.TopCenter).padding(top = 12.dp),
+                                enter = androidx.compose.animation.slideInVertically { -it },
+                                exit = androidx.compose.animation.slideOutVertically { -it },
+                            ) {
+                                GsButton(onClick = CarFullscreen::exit, modifier = Modifier.height(48.dp)) {
+                                    Icon(MediaIcons.FullscreenExit, contentDescription = null, modifier = Modifier.size(22.dp))
+                                    Spacer(Modifier.width(8.dp))
+                                    Text("Exit full screen", style = MaterialTheme.typography.titleMedium)
+                                }
+                            }
                         }
                     }
-                    // The keyboard takes the nav bar's row instead of squeezing in above it -
-                    // nothing on the nav bar is useful mid-type, and the screen is too small to
-                    // show both.
-                    val keyboardVisible by CarKeyboardVisibility.state
-                    if (!keyboardVisible) CarNavBar(navigator)
                 }
                 // Over everything, nav bar included: a long press on an app, anywhere.
                 AppMenu(navigator, rememberRunningApps())
@@ -284,6 +357,14 @@ fun CarUi() {
     }
 }
 
+private val NAV_BAR_HEIGHT = 56.dp
+
+/**
+ * How much of the bottom of Home the floating nav bar covers right now: its height while it shows,
+ * zero while it's hidden or when it has a row of its own.
+ */
+internal val LocalNavBarInset = androidx.compose.runtime.compositionLocalOf { 0.dp }
+
 /**
  * A single blocking screen, shown once per install before anything else the car screen can show -
  * Home included. The phone's own setup guide carries the same warning, but a driver who plugs in
@@ -462,7 +543,7 @@ private fun CarNavBar(navigator: CarNavigator) {
     val running = rememberRunningApps()
 
     Surface(color = MaterialTheme.colorScheme.surfaceContainer) {
-        BoxWithConstraints(Modifier.fillMaxWidth().height(56.dp).padding(horizontal = 10.dp)) {
+        BoxWithConstraints(Modifier.fillMaxWidth().height(NAV_BAR_HEIGHT).padding(horizontal = 10.dp)) {
             Row(Modifier.fillMaxSize(), verticalAlignment = Alignment.CenterVertically) {
                 // Home and Apps are two different places now, not a toggle on one button - the
                 // breadcrumb trail is how you retrace your steps, but reaching for either of
@@ -488,12 +569,16 @@ private fun CarNavBar(navigator: CarNavigator) {
 
                 // Next turn first, off the map only; the player shares the space when it fits,
                 // and gives way to the turn when it doesn't.
+                // A call takes the player's place until it ends.
                 val turn = rememberNextTurn().takeIf { navigator.current != CarScreen.Home }
+                val call = CarCalls.state.collectAsState().value as? CallUiState.Active
                 BoxWithConstraints(Modifier.weight(1f).padding(horizontal = 16.dp), contentAlignment = Alignment.Center) {
                     val roomForBoth = maxWidth >= TURN_AND_PLAYER_MIN_WIDTH
                     Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(10.dp)) {
-                        turn?.let { NavTurnPill(it) { navigator.home() } }
-                        if (turn == null || roomForBoth) {
+                        if (call == null || roomForBoth) turn?.let { NavTurnPill(it) { navigator.home() } }
+                        if (call != null) {
+                            NavCallPill(call, Modifier.weight(1f, fill = false))
+                        } else if (turn == null || roomForBoth) {
                             NavNowPlaying(navigator, selected = navigator.current == CarScreen.Media, modifier = Modifier.weight(1f, fill = false))
                         }
                     }
@@ -760,6 +845,58 @@ private fun NavTurnPill(turn: NextTurn, onClick: () -> Unit) {
     }
 }
 
+/** The call under way: who, how long, and Mute and End right here. Ringing has its own screen. */
+@Composable
+private fun NavCallPill(call: CallUiState.Active, modifier: Modifier = Modifier) {
+    val context = LocalContext.current.applicationContext
+    val muted by CarCalls.muted.collectAsState()
+    val elapsed by produceState(0L, call.since) {
+        while (true) {
+            value = (android.os.SystemClock.uptimeMillis() - call.since) / 1000
+            delay(1000 - (android.os.SystemClock.uptimeMillis() - call.since) % 1000)
+        }
+    }
+    val scheme = MaterialTheme.colorScheme
+    Surface(
+        modifier = modifier.height(44.dp),
+        shape = RoundedCornerShape(14.dp),
+        color = scheme.secondaryContainer,
+        contentColor = scheme.onSecondaryContainer,
+    ) {
+        Row(
+            Modifier.fillMaxHeight().padding(start = 12.dp, end = 4.dp),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.spacedBy(6.dp),
+        ) {
+            Icon(Icons.Filled.Call, contentDescription = null, modifier = Modifier.size(20.dp))
+            Text(
+                call.caller?.label ?: "On a call",
+                style = MaterialTheme.typography.titleSmall,
+                fontWeight = FontWeight.SemiBold,
+                maxLines = 1,
+                overflow = TextOverflow.Ellipsis,
+                modifier = Modifier.weight(1f, fill = false),
+            )
+            Text(
+                "%d:%02d".format(elapsed / 60, elapsed % 60),
+                style = MaterialTheme.typography.titleSmall,
+                maxLines = 1,
+            )
+            Spacer(Modifier.width(2.dp))
+            GsIconButton(
+                if (muted) MediaIcons.MicOff else MediaIcons.Mic,
+                if (muted) "Unmute" else "Mute",
+                CarCalls::toggleMute,
+                tone = if (muted) GsTone.Primary else GsTone.Neutral, size = 36.dp, iconSize = 22.dp,
+            )
+            GsIconButton(
+                MediaIcons.CallEnd, "End call", { CarCalls.end(context) },
+                colors = GsColors(scheme.error, scheme.onError), size = 36.dp, iconSize = 22.dp,
+            )
+        }
+    }
+}
+
 /** "Title - Artist" on one line. The text itself cuts it off, and only where the pill runs out of room. */
 private fun nowPlayingLabel(title: String, artist: String): String =
     listOf(title.trim(), artist.trim()).filter { it.isNotEmpty() }.joinToString(" - ")

gearslip/src/main/java/app/seb3thehacker/gearslip/car/ClusterNav.kt

@@ -24,23 +24,36 @@ import app.seb3thehacker.gearslip.Protobuf
  */
 class ClusterNav(
     val channelId: Int,
+    minimumIntervalMs: Long = 0,
     private val sendOnChannel: (messageId: Int, body: ByteArray) -> Unit,
 ) {
+    private val updateIntervalMs = maxOf(TICK_MS, minimumIntervalMs)
     @Volatile private var running = false
+    private var worker: Thread? = null
+    private var updatesRequested = true
     private var sentStatus = -1
     private var sentTurn: String? = null
     private var sentDistance: String? = null
 
+    @Synchronized
     fun onMessage(messageId: Int, body: ByteArray) {
         when (messageId) {
             MSG_CHANNEL_OPEN_RESPONSE -> {
-                val status = Protobuf.readInt32Field(body, 1) ?: 0
+                val status = Protobuf.readInt32Field(body, 1)
                 GearslipLog.i("cluster: <- ChannelOpenResponse: status=$status")
                 if (status == 0) start()
             }
-            // The car saying when it wants turns. Sending all along is harmless, so these are only logged.
-            MSG_START -> GearslipLog.i("cluster: <- start")
-            MSG_STOP -> GearslipLog.i("cluster: <- stop")
+            MSG_START -> {
+                updatesRequested = true
+                sentStatus = -1
+                sentTurn = null
+                sentDistance = null
+                GearslipLog.i("cluster: <- start")
+            }
+            MSG_STOP -> {
+                updatesRequested = false
+                GearslipLog.i("cluster: <- stop")
+            }
             else -> GearslipLog.i("cluster: <- unhandled message id=$messageId (${body.size} bytes)")
         }
     }
@@ -48,19 +61,28 @@ class ClusterNav(
     private fun start() {
         if (running) return
         running = true
-        Thread({
+        worker = Thread({
             while (running) {
                 runCatching { tick() }.onFailure { GearslipLog.w("cluster: ${it.message}") }
-                Thread.sleep(TICK_MS)
+                try {
+                    Thread.sleep(updateIntervalMs)
+                } catch (_: InterruptedException) {
+                    return@Thread
+                }
             }
-        }, "gearslip-cluster").start()
+        }, "gearslip-cluster").also { it.start() }
     }
 
+    @Synchronized
     fun stop() {
         running = false
+        worker?.interrupt()
+        worker = null
     }
 
+    @Synchronized
     private fun tick() {
+        if (!running || !updatesRequested) return
         val turn = NavTurn.current()
         val status = when {
             turn == null -> STATUS_INACTIVE
@@ -82,7 +104,7 @@ class ClusterNav(
         val maneuver = step.maneuver
         val (event, side) = maneuver?.let { eventFor(it.type) } ?: (EVENT_UNKNOWN to SIDE_UNSPECIFIED)
         val road = step.road.text().ifBlank { step.cue.text() }
-        val key = "$road|$event|$side|${maneuver?.roundaboutExitNumber}"
+        val key = "$road|$event|$side|${maneuver?.roundaboutExitNumber}|${maneuver?.roundaboutExitAngle}"
         if (key == sentTurn) return
         sentTurn = key
         var body = Protobuf.stringField(1, road) +

gearslip/src/main/java/app/seb3thehacker/gearslip/car/DirectionsVoice.kt

@@ -27,7 +27,8 @@ import kotlin.math.roundToInt
  * same turn the instrument cluster gets ([NavTurn]) and says it itself: once when the turn comes
  * up, again a kilometre or so out on a long stretch, and once more just before it. The words are
  * rendered with the phone's text-to-speech to a file, never played on the phone, and streamed to
- * the car, which ducks the music under them the way it does for real Android Auto.
+ * the car, which ducks the music under them the way it does for real Android Auto. When the music
+ * isn't Gearslip's, each announcement first asks the car for its speakers, as Android Auto does.
  *
  * Nothing spoken is logged: road names are where the driver is going.
  */
@@ -42,7 +43,10 @@ object DirectionsVoice {
 
     @Volatile private var link: AudioLink? = null
     @Volatile private var running = false
-    private val speaker = Executors.newSingleThreadExecutor { Thread(it, "gearslip-directions").apply { isDaemon = true } }
+    @Volatile private var musicIsOurs: () -> Boolean = { false }
+    private val speaker = Executors.newSingleThreadScheduledExecutor { Thread(it, "gearslip-directions").apply { isDaemon = true } }
+    /** Counts announcements, so a hand-back scheduled after one is dropped if another has begun. */
+    private var spoken = 0
     @Volatile private var latest = 0
 
     private var turnKey: String? = null
@@ -62,8 +66,9 @@ object DirectionsVoice {
     }
 
     /** The car opened its directions sink: start following the map app's turns. */
-    fun attach(link: AudioLink) {
+    fun attach(link: AudioLink, musicIsOurs: () -> Boolean) {
         this.link = link
+        this.musicIsOurs = musicIsOurs
         GearslipLog.i("guidance: the car offered a directions sink at ${link.sampleRate}Hz x${link.channels}")
         if (running) return
         running = true
@@ -82,16 +87,26 @@ object DirectionsVoice {
         running = false
     }
 
+    /** Why the last turn wasn't spoken, so the log says it once rather than every tick. */
+    private var silentBecause: String? = null
+
+    private fun quiet(reason: String) {
+        if (silentBecause == reason) return
+        silentBecause = reason
+        GearslipLog.i("guidance: not speaking - $reason")
+    }
+
     private fun tick() {
-        if (!CarSettings.speakDirections.value) return
         val turn = NavTurn.current()
         if (turn == null) {
             turnKey = null
             return
         }
-        if (turn.rerouting) return
+        if (!CarSettings.speakDirections.value) return quiet("Spoken directions is off in the car's Settings")
+        if (turn.rerouting) return quiet("the map app is rerouting")
         val step = turn.step
-        val instruction = instruction(step) ?: return
+        val instruction = instruction(step) ?: return quiet("the map app gave this turn no words")
+        silentBecause = null
         val meters = turn.distance?.let(NavTurn::toMeters)
         val close = (turn.seconds != null && turn.seconds <= NEAR_SECONDS) || (meters != null && meters <= NEAR_METERS)
 
@@ -223,7 +238,16 @@ object DirectionsVoice {
             GearslipLog.w("guidance: text-to-speech gave audio Gearslip can't read")
             return
         }
-        stream(sink, pcm)
+        // Logged before speaking too, so a car that dies mid-announcement shows what it was doing.
+        GearslipLog.i("guidance: speaking a turn")
+        // Held through back-to-back prompts rather than asked for and given back each time.
+        if (!musicIsOurs()) sink.askForSpeakers()
+        val turn = ++spoken
+        try {
+            stream(sink, pcm)
+        } finally {
+            speaker.schedule({ if (turn == spoken) sink.handBackSpeakers() }, HOLD_MS, TimeUnit.MILLISECONDS)
+        }
         GearslipLog.i("guidance: spoke a turn (${pcm.size / (2 * sink.channels) * 1000 / sink.sampleRate} ms)")
     }
 
@@ -321,6 +345,7 @@ object DirectionsVoice {
     private const val PREPARE_FROM_METERS = 2_500
     private const val PREPARE_AT_METERS = 1_000
     private const val LEAD_MS = 100L
+    private const val HOLD_MS = 2_000L
     private const val SYNTH_TIMEOUT_S = 10L
     private val ORDINALS = listOf("first", "second", "third", "fourth", "fifth", "sixth", "seventh", "eighth")
 }

gearslip/src/main/java/app/seb3thehacker/gearslip/car/MapControlsWake.kt

@@ -11,27 +11,35 @@ import android.os.SystemClock
  *
  * They fade out after [IDLE_MS] with no touch anywhere on the car screen, to leave the map clear,
  * and any touch brings them back. [touch] is called for every pointer event and is cheap: it only
- * writes state when the buttons were actually hidden.
+ * writes state when the buttons were actually hidden. The nav bar, when set to hide, goes the
+ * same way but waits longer ([NAV_BAR_IDLE_MS]).
  */
 class MapControlsWake {
 
     var awake by mutableStateOf(true)
         private set
 
+    var navBarAwake by mutableStateOf(true)
+        private set
+
     private var lastTouch = SystemClock.uptimeMillis()
 
     fun touch() {
         lastTouch = SystemClock.uptimeMillis()
         if (!awake) awake = true
+        if (!navBarAwake) navBarAwake = true
     }
 
     /** Called on a timer; hides the buttons once nothing has touched the screen for [IDLE_MS]. */
     fun tick() {
-        if (awake && SystemClock.uptimeMillis() - lastTouch >= IDLE_MS) awake = false
+        val idle = SystemClock.uptimeMillis() - lastTouch
+        if (awake && idle >= IDLE_MS) awake = false
+        if (navBarAwake && idle >= NAV_BAR_IDLE_MS) navBarAwake = false
     }
 
     companion object {
         const val IDLE_MS = 4_000L
+        const val NAV_BAR_IDLE_MS = 8_000L
     }
 }
 

gearslip/src/main/java/app/seb3thehacker/gearslip/car/MediaScreen.kt

@@ -688,6 +688,12 @@ internal object MediaIcons {
     val RepeatOne = icon("RepeatOne", "M7,7h10v3l4,-4 -4,-4v3L5,5v6h2L7,7zM17,17L7,17v-3l-4,4 4,4v-3h12v-6h-2v4zM13,15L13,9h-1l-2,1v1h1.5v4L13,15z")
     /** A screen with a filled right-hand panel: "put the player beside the map". */
     val DockRight = icon("DockRight", "M2,4h20v16H2zM4,6h10v12H4z", PathFillType.EvenOdd)
+    val Fullscreen = icon("Fullscreen", "M7,14L5,14v5h5v-2L7,17v-3zM5,10h2L7,7h3L10,5L5,5v5zM17,17h-3v2h5v-5h-2v3zM14,5v2h3v3h2L19,5h-5z")
+    val FullscreenExit = icon("FullscreenExit", "M5,16h3v3h2v-5L5,14v2zM8,8L5,8v2h5L10,5L8,5v3zM14,19h2v-3h3v-2h-5v5zM16,8L16,5h-2v5h5L19,8h-3z")
+
+    val CallEnd = icon("CallEnd", "M12,9c-1.6,0 -3.15,0.25 -4.6,0.72v3.1c0,0.39 -0.23,0.74 -0.56,0.9 -0.98,0.49 -1.87,1.12 -2.66,1.85 -0.18,0.18 -0.43,0.28 -0.7,0.28 -0.28,0 -0.53,-0.11 -0.71,-0.29L0.29,13.08c-0.18,-0.17 -0.29,-0.42 -0.29,-0.7 0,-0.28 0.11,-0.53 0.29,-0.71C3.34,8.78 7.46,7 12,7s8.66,1.78 11.71,4.67c0.18,0.18 0.29,0.43 0.29,0.71 0,0.28 -0.11,0.53 -0.29,0.71l-2.48,2.48c-0.18,0.18 -0.43,0.29 -0.71,0.29 -0.27,0 -0.52,-0.11 -0.7,-0.28 -0.79,-0.74 -1.69,-1.36 -2.67,-1.85 -0.33,-0.16 -0.56,-0.5 -0.56,-0.9v-3.1C15.15,9.25 13.6,9 12,9z")
+    val Mic = icon("Mic", "M12,14c1.66,0 2.99,-1.34 2.99,-3L15,5c0,-1.66 -1.34,-3 -3,-3S9,3.34 9,5v6c0,1.66 1.34,3 3,3zM17.3,11c0,3 -2.54,5.1 -5.3,5.1S6.7,14 6.7,11L5,11c0,3.41 2.72,6.23 6,6.72L11,21h2v-3.28c3.28,-0.48 6,-3.3 6,-6.72h-1.7z")
+    val MicOff = icon("MicOff", "M19,11h-1.7c0,0.74 -0.16,1.43 -0.43,2.05l1.23,1.23c0.56,-0.98 0.9,-2.09 0.9,-3.28zM14.98,11.17c0,-0.06 0.02,-0.11 0.02,-0.17L15,5c0,-1.66 -1.34,-3 -3,-3S9,3.34 9,5v0.18l5.98,5.99zM4.27,3L3,4.27l6.01,6.01L9,11c0,1.66 1.33,3 2.99,3 0.22,0 0.44,-0.03 0.65,-0.08l1.66,1.66c-0.71,0.33 -1.5,0.52 -2.31,0.52 -2.76,0 -5.3,-2.1 -5.3,-5.1L5,11c0,3.41 2.72,6.23 6,6.72L11,21h2v-3.28c0.91,-0.13 1.77,-0.45 2.54,-0.9L19.73,21 21,19.73 4.27,3z")
 
     private fun icon(name: String, path: String, fillType: PathFillType = PathFillType.NonZero) = ImageVector.Builder(
         name, 24.dp, 24.dp, 24f, 24f,

gearslip/src/main/java/app/seb3thehacker/gearslip/car/PhoneDialerScreen.kt

@@ -8,6 +8,7 @@ import android.content.pm.PackageManager
 import android.net.Uri
 import android.provider.ContactsContract
 import android.provider.Settings
+import app.seb3thehacker.gearslip.GearslipLog
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.interaction.MutableInteractionSource
@@ -80,14 +81,24 @@ internal fun loadContacts(context: Context): List<Contact> {
     return out.distinctBy { it.number }
 }
 
+/**
+ * Places the call through Telecom directly. Starting ACTION_CALL from here launched the system's
+ * call activity onto the car's display, which Android refuses for another app's activity, and
+ * from the background, which it blocks too - so the call never went out.
+ */
 internal fun placeCall(context: Context, number: String) {
     if (number.isBlank()) return
-    if (context.checkSelfPermission(Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) return
-    runCatching {
-        context.startActivity(
-            Intent(Intent.ACTION_CALL, Uri.parse("tel:${Uri.encode(number)}")).addFlags(Intent.FLAG_ACTIVITY_NEW_TASK),
-        )
+    if (context.checkSelfPermission(Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) {
+        GearslipLog.w("calls: can't place a call without CALL_PHONE")
+        return
     }
+    val telecom = context.getSystemService(android.telecom.TelecomManager::class.java)
+    runCatching { telecom!!.placeCall(Uri.fromParts("tel", number, null), null) }
+        .onSuccess {
+            GearslipLog.i("calls: placing a call")
+            app.seb3thehacker.gearslip.call.CarCalls.outgoingCall(context, number)
+        }
+        .onFailure { GearslipLog.w("calls: placing a call failed: ${it.message}") }
 }
 
 /** A call another car screen wants to place - a number on a place page - waiting on the driver. */

gearslip/src/main/java/app/seb3thehacker/gearslip/car/TemplateChrome.kt

@@ -2,6 +2,13 @@ package app.seb3thehacker.gearslip.car
 
 import app.seb3thehacker.gearslip.car.theme.*
 import android.graphics.Rect
+import androidx.compose.foundation.layout.widthIn
+import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.compositionLocalOf
+import androidx.compose.runtime.mutableStateMapOf
+import androidx.compose.ui.layout.boundsInWindow
+import androidx.compose.ui.layout.onGloballyPositioned
+import androidx.compose.ui.geometry.Rect as ComposeRect
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
@@ -10,6 +17,7 @@ import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
@@ -86,89 +94,183 @@ fun TemplateChrome(template: Template?, modifier: Modifier = Modifier) {
  * How much of the surface Gearslip's chrome covers, so the app can keep what matters clear of
  * it. Expressed as the visible rectangle within a [width] x [height] surface.
  *
+ * Navigation's cards are measured where they land ([measured], from [ChromeCover]); an app
+ * centres its position marker in this rectangle, so a guess puts the marker under the card.
  * A template that isn't map-backed covers the surface completely, and reporting an empty
  * rectangle is how the app is told to stop bothering.
  */
-fun visibleAreaFor(template: Template?, width: Int, height: Int): Rect = when (template) {
-    is NavigationTemplate -> Rect(0, 0, width, (height * (1f - ESTIMATE_FRACTION)).toInt())
+fun visibleAreaFor(template: Template?, width: Int, height: Int, measured: Rect? = null): Rect = when (template) {
+    is NavigationTemplate -> measured ?: Rect(0, 0, width, height)
     is MapWithContentTemplate, is MapTemplate, is PlaceListNavigationTemplate,
     is RoutePreviewNavigationTemplate, is PlaceListMapTemplate,
-    -> Rect((width * CONTENT_PANE_FRACTION).toInt(), 0, width, height)
+    -> Rect((width * CONTENT_PANE_FRACTION).toInt(), 0, width, measured?.bottom ?: height)
     null -> Rect(0, 0, width, height)
     else -> Rect(0, 0, 0, 0)
 }
 
+/** The side of the map a piece of chrome sits against, and so the side it shrinks the visible area from. */
+internal enum class CoverEdge { TOP, BOTTOM, END }
+
+/**
+ * Where the chrome over the map actually landed, in window pixels. The map buttons count even
+ * while faded out, or whatever an app draws in a corner (Waze's speedometer) is under them the
+ * moment they come back.
+ */
+internal class ChromeCover {
+    private val pieces = mutableStateMapOf<String, Pair<CoverEdge, ComposeRect>>()
+
+    fun put(key: String, edge: CoverEdge, bounds: ComposeRect) {
+        val piece = edge to bounds
+        if (pieces[key] != piece) pieces[key] = piece
+    }
+
+    fun remove(key: String) {
+        pieces.remove(key)
+    }
+
+    /** What is left of a [width] x [height] surface at [surface] (window pixels), in surface pixels. */
+    fun visibleWithin(surface: ComposeRect, width: Int, height: Int): Rect {
+        var left = 0f
+        var top = 0f
+        var right = width.toFloat()
+        var bottom = height.toFloat()
+        pieces.values.forEach { (edge, b) ->
+            when (edge) {
+                CoverEdge.TOP -> top = maxOf(top, b.bottom - surface.top)
+                CoverEdge.BOTTOM -> bottom = minOf(bottom, b.top - surface.top)
+                CoverEdge.END -> right = minOf(right, b.left - surface.left)
+            }
+        }
+        // Never hand an app nothing to draw in, however the cards end up.
+        if (right - left < width / 4f) { left = 0f; right = width.toFloat() }
+        if (bottom - top < height / 4f) { top = 0f; bottom = height.toFloat() }
+        return Rect(left.toInt(), top.toInt(), right.toInt(), bottom.toInt())
+    }
+}
+
+internal val LocalChromeCover = compositionLocalOf<ChromeCover?> { null }
+
+/**
+ * The floating nav bar, as far as the app's map is concerned. Its full [height] at once rather
+ * than following the slide, so the app is told once instead of every frame.
+ */
+@Composable
+internal fun BottomCover(height: androidx.compose.ui.unit.Dp, modifier: Modifier = Modifier) {
+    Box(modifier.fillMaxWidth().height(height).covers("nav-bar", CoverEdge.BOTTOM))
+}
+
+/** Records where this lands, padding included, until it leaves the screen. */
+@Composable
+internal fun Modifier.covers(key: String, edge: CoverEdge): Modifier {
+    val cover = LocalChromeCover.current ?: return this
+    DisposableEffect(cover, key) { onDispose { cover.remove(key) } }
+    return onGloballyPositioned { cover.put(key, edge, it.boundsInWindow()) }
+}
+
 // --- navigation ------------------------------------------------------------------------------
 
 @Composable
 private fun NavigationChrome(template: NavigationTemplate, modifier: Modifier) {
     val pan by CarServices.nav.panMode.collectAsState()
-    Box(modifier.fillMaxWidth()) {
-        if (!pan) (template.navigationInfo as? RoutingInfo)?.let {
-            RoutingCard(it, Modifier.align(Alignment.TopStart).padding(12.dp).width(320.dp))
+    // Pan mode clears the map for looking around: only the buttons stay.
+    val routing = (template.navigationInfo as? RoutingInfo)?.takeUnless { pan }
+    val estimate = template.destinationTravelEstimate?.takeUnless { pan }
+    NavigationBars(template, routing, estimate, modifier)
+}
+
+/**
+ * The turn in one short bar across the top, the arrival time in another along the bottom, so the
+ * map keeps its full width. Neither grows past [NAV_BAR_MAX_WIDTH]. The bottom one is short and
+ * left out of the visible area on purpose, so a speedometer in the app's bottom corner sits level
+ * with it rather than stacked above it. The map buttons sit between them on the right.
+ */
+@Composable
+private fun NavigationBars(
+    template: NavigationTemplate,
+    routing: RoutingInfo?,
+    estimate: TravelEstimate?,
+    modifier: Modifier,
+) {
+    val pan by CarServices.nav.panMode.collectAsState()
+    Column(modifier.fillMaxSize()) {
+        routing?.let {
+            RoutingBar(
+                it,
+                Modifier.covers("nav-top", CoverEdge.TOP).padding(start = 12.dp, top = 12.dp, end = 12.dp)
+                    .widthIn(max = NAV_BAR_MAX_WIDTH).fillMaxWidth(),
+            )
         }
-        RightEdgeControls(
-            if (pan) null else template.actionStrip,
-            template.mapActionStrip,
-            Modifier.align(Alignment.TopEnd).padding(12.dp),
-        )
-        if (!pan) template.destinationTravelEstimate?.let {
-            TravelEstimateBar(it, Modifier.align(Alignment.BottomStart).padding(12.dp))
+        Row(Modifier.weight(1f).fillMaxWidth()) {
+            Box(Modifier.weight(1f).fillMaxHeight()) {
+                estimate?.let {
+                    TravelEstimateBar(
+                        it,
+                        Modifier.align(Alignment.BottomStart).padding(12.dp)
+                            .widthIn(max = NAV_BAR_MAX_WIDTH),
+                    )
+                }
+            }
+            RightEdgeControls(
+                if (pan) null else template.actionStrip,
+                template.mapActionStrip,
+                Modifier.padding(12.dp),
+                // Only the column: the app's own buttons are a wide row up top, over the map's
+                // edge rather than where a speedometer or the like would go.
+                mapActionsModifier = Modifier.covers("nav-buttons", CoverEdge.END),
+            )
         }
     }
 }
 
-/** The manoeuvre card: what to do next, how far away it is, and onto what road. */
+/** The manoeuvre in one row: arrow, distance, what to do, onto what road, and lanes or the next turn. */
 @Composable
-private fun RoutingCard(info: RoutingInfo, modifier: Modifier = Modifier) {
+private fun RoutingBar(info: RoutingInfo, modifier: Modifier = Modifier) {
     if (info.isLoading) {
         ChromeSurface(modifier) {
-            Text("Finding a route…", Modifier.padding(16.dp), style = ChromeType.title)
+            Text("Finding a route…", Modifier.padding(horizontal = 16.dp, vertical = 12.dp), style = ChromeType.title)
         }
         return
     }
 
     val step = info.currentStep ?: return
     ChromeSurface(modifier) {
-        Column(Modifier.padding(14.dp)) {
+        Column(Modifier.padding(horizontal = 14.dp, vertical = 10.dp)) {
             Row(verticalAlignment = Alignment.CenterVertically) {
-                CarGlyph(step.maneuver?.icon, Modifier.size(44.dp))
+                CarGlyph(step.maneuver?.icon, Modifier.size(40.dp))
                 Spacer(Modifier.width(12.dp))
-                Column(Modifier.weight(1f)) {
-                    val distance = info.currentDistance.display()
-                    if (distance.isNotEmpty()) {
-                        Text(distance, style = ChromeType.headline)
-                    }
-                    Text(step.cue.text(), style = ChromeType.title, maxLines = 2, overflow = TextOverflow.Ellipsis)
+                val distance = info.currentDistance.display()
+                if (distance.isNotEmpty()) {
+                    Text(distance, style = ChromeType.headline, maxLines = 1)
+                    Spacer(Modifier.width(14.dp))
                 }
-            }
-            val road = step.road.text()
-            if (road.isNotEmpty()) {
-                Text(
-                    road,
-                    style = ChromeType.body,
-                    color = MaterialTheme.colorScheme.onSurfaceVariant,
-                    maxLines = 1,
-                    overflow = TextOverflow.Ellipsis,
-                )
-            }
-            // Neither is sent by every app - most say only "turn left" and trust the driver to
-            // find the lane themselves - so both are drawn only when there is something to draw.
-            info.junctionImage?.let { junction ->
-                Spacer(Modifier.height(10.dp))
-                JunctionImage(junction)
-            }
-            LaneGuidance(step, Modifier.padding(top = 10.dp))
-            info.nextStep?.let { next ->
-                Spacer(Modifier.height(8.dp))
-                Row(verticalAlignment = Alignment.CenterVertically) {
+                Column(Modifier.weight(1f)) {
+                    Text(step.cue.text(), style = ChromeType.title, maxLines = 1, overflow = TextOverflow.Ellipsis)
+                    val road = step.road.text()
+                    if (road.isNotEmpty()) {
+                        Text(
+                            road,
+                            style = ChromeType.body,
+                            color = MaterialTheme.colorScheme.onSurfaceVariant,
+                            maxLines = 1,
+                            overflow = TextOverflow.Ellipsis,
+                        )
+                    }
+                }
+                val next = info.nextStep
+                if (step.lanesImage != null || step.lanes.orEmpty().isNotEmpty()) {
+                    LaneGuidance(step, Modifier.padding(start = 12.dp).widthIn(max = 200.dp).heightIn(max = 48.dp))
+                } else if (next != null) {
+                    Spacer(Modifier.width(12.dp))
                     Text("then", style = ChromeType.label, color = MaterialTheme.colorScheme.onSurfaceVariant)
                     Spacer(Modifier.width(8.dp))
-                    CarGlyph(next.maneuver?.icon, Modifier.size(20.dp))
-                    Spacer(Modifier.width(8.dp))
-                    Text(next.cue.text(), style = ChromeType.body, maxLines = 1, overflow = TextOverflow.Ellipsis)
+                    CarGlyph(next.maneuver?.icon, Modifier.size(24.dp))
                 }
             }
+            // Rare, and only where an arrow can't explain the junction: worth the bar growing for.
+            info.junctionImage?.let { junction ->
+                Spacer(Modifier.height(8.dp))
+                JunctionImage(junction)
+            }
         }
     }
 }
@@ -244,9 +346,8 @@ private fun LaneDirection?.turnDegrees(): Float = when (this?.shape) {
 
 /**
  * The trip at a glance: time and distance left, the clock time it ends at, and - beside them,
- * where a thumb reaches - the app's own way to stop navigating. A floating card rather than a
- * full-width bar, so it reads as one thing beside the manoeuvre card above it instead of a strip
- * that happens to hold three numbers. The close button is Gearslip's own, not the app's: an
+ * where a thumb reaches - the app's own way to stop navigating. One short line along the bottom,
+ * stopping short of the map buttons. The close button is Gearslip's own, not the app's: an
  * actionStrip's actions carry no flag saying which one (if any) means "stop navigating" - the
  * first button here turned out to be a mute toggle, not an exit - so this leaves the app the way
  * going Home already does, rather than guess at the app's own controls and risk getting it wrong.
@@ -265,7 +366,7 @@ private fun TravelEstimateBar(estimate: TravelEstimate, modifier: Modifier = Mod
         trip.takeIf { it.isNotEmpty() },
     ).joinToString("  •  ")
 
-    // The same solid card the manoeuvre card above it uses - one surface for the whole map
+    // The same solid card the manoeuvre bar above it uses - one surface for the whole map
     // chrome, rather than this one spot styled on its own as a bar over the map.
     ChromeSurface(modifier, shadowElevation = 8.dp) {
         val dark = MaterialTheme.colorScheme.surface.luminanceIsDark()
@@ -288,17 +389,23 @@ private fun TravelEstimateBar(estimate: TravelEstimate, modifier: Modifier = Mod
                 shape = CircleShape,
             )
             Spacer(Modifier.width(10.dp))
-            Column {
-                if (time.isNotEmpty()) {
-                    Text(
-                        time,
-                        style = ChromeType.headline,
-                        color = estimate.remainingTimeColor.color(dark, MaterialTheme.colorScheme.onSurface),
-                    )
-                }
-                if (detail.isNotEmpty()) {
-                    Text(detail, style = ChromeType.body, color = MaterialTheme.colorScheme.onSurfaceVariant)
-                }
+            if (time.isNotEmpty()) {
+                Text(
+                    time,
+                    style = ChromeType.headline,
+                    color = estimate.remainingTimeColor.color(dark, MaterialTheme.colorScheme.onSurface),
+                    maxLines = 1,
+                )
+            }
+            if (detail.isNotEmpty()) {
+                Spacer(Modifier.width(16.dp))
+                Text(
+                    detail,
+                    style = ChromeType.body,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    maxLines = 1,
+                    overflow = TextOverflow.Ellipsis,
+                )
             }
         }
     }
@@ -454,8 +561,9 @@ private fun ListPane(
 /** Fraction of the surface the content pane covers beside a map. */
 private const val CONTENT_PANE_FRACTION = 0.42f
 
-/** Fraction of the surface the travel-estimate bar covers along the bottom. */
-private const val ESTIMATE_FRACTION = 0.14f
+
+/** Past this the bars only spread the same words further apart, across a map left with no music beside it. */
+private val NAV_BAR_MAX_WIDTH = 460.dp
 
 /** Search, sign-in and the like are laid out for a whole column, so they keep one. */
 private fun Template?.needsFullHeight() =

gearslip/src/main/java/app/seb3thehacker/gearslip/car/TemplateParts.kt

@@ -222,6 +222,8 @@ internal fun RightEdgeControls(
     actionStrip: ActionStrip?,
     mapActionStrip: ActionStrip?,
     modifier: Modifier = Modifier,
+    /** For the stack of map buttons alone, without the row of the app's own above it. */
+    mapActionsModifier: Modifier = Modifier,
 ) {
     val actions = actionStrip?.actions.orEmpty().filter { it.isDrawable() }
     val mapActions = mapActionStrip?.actions.orEmpty().filter { it.isDrawable() }
@@ -263,7 +265,15 @@ internal fun RightEdgeControls(
                 actions.forEach { ActionButton(it) }
             }
         }
-        mapActions.forEach { ActionButton(it) }
+        if (mapActions.isNotEmpty()) {
+            Column(
+                mapActionsModifier,
+                horizontalAlignment = Alignment.End,
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+            ) {
+                mapActions.forEach { ActionButton(it) }
+            }
+        }
     }
 }
 

gearslip/src/main/java/app/seb3thehacker/gearslip/car/WebApp.kt

@@ -2,7 +2,14 @@ package app.seb3thehacker.gearslip.car
 
 import android.os.Handler
 import android.os.Looper
+import android.view.View
+import android.view.ViewGroup
 import android.webkit.JavascriptInterface
+import android.webkit.WebChromeClient
+import android.widget.FrameLayout
+import androidx.compose.foundation.layout.Box
+import androidx.compose.runtime.LaunchedEffect
+import app.seb3thehacker.gearslip.car.theme.GsIconButton
 import android.webkit.WebResourceError
 import android.webkit.WebResourceRequest
 import android.webkit.WebResourceResponse
@@ -43,11 +50,30 @@ fun WebApp(content: String) {
     val ring = String.format("#%06X", MaterialTheme.colorScheme.primary.toArgb() and 0xFFFFFF)
     var web by remember { mutableStateOf<WebView?>(null) }
     var fieldText by remember { mutableStateOf<String?>(null) }
+    // A page's own full screen, such as a video's: the view to show, and how to hand it back.
+    var pageFullscreen by remember { mutableStateOf<Pair<View, WebChromeClient.CustomViewCallback>?>(null) }
+    // Whether the video asked for full screen, rather than the driver from the header: ending
+    // the video's then leaves full screen too, instead of stranding them in it.
+    var videoMadeFullscreen by remember { mutableStateOf(false) }
+    val fullscreen = CarFullscreen.active
+
+    // Leaving the browser ends full screen, whoever started it.
+    DisposableEffect(Unit) { onDispose { CarFullscreen.exit() } }
+    // The way out of full screen also ends the page's.
+    LaunchedEffect(fullscreen) {
+        if (!fullscreen) pageFullscreen?.let { (_, callback) ->
+            pageFullscreen = null
+            callback.onCustomViewHidden()
+        }
+    }
 
     DisposableEffect(web) {
         navigator.backInterceptor = {
             val view = web
-            if (view != null && view.canGoBack()) {
+            if (CarFullscreen.active) {
+                CarFullscreen.exit()
+                true
+            } else if (view != null && view.canGoBack()) {
                 view.goBack()
                 true
             } else {
@@ -59,9 +85,14 @@ fun WebApp(content: String) {
 
     Column(Modifier.fillMaxSize()) {
         // Back steps through the page's history first (the interceptor above), then leaves.
-        ScreenHeader("Browser", Modifier.padding(horizontal = 16.dp, vertical = 8.dp))
+        if (!fullscreen) {
+            ScreenHeader("Browser", Modifier.padding(horizontal = 16.dp, vertical = 8.dp)) {
+                GsIconButton(MediaIcons.Fullscreen, "Full screen", CarFullscreen::enter)
+            }
+        }
+        Box(Modifier.weight(1f).fillMaxSize()) {
         AndroidView(
-            modifier = Modifier.weight(1f).fillMaxSize(),
+            modifier = Modifier.fillMaxSize(),
             factory = { context ->
                 WebView(context).apply {
                     settings.javaScriptEnabled = true
@@ -69,6 +100,19 @@ fun WebApp(content: String) {
                     settings.loadWithOverviewMode = true
                     settings.useWideViewPort = true
                     webViewClient = LoggingClient(ring)
+                    webChromeClient = object : WebChromeClient() {
+                        override fun onShowCustomView(view: View, callback: CustomViewCallback) {
+                            videoMadeFullscreen = !CarFullscreen.active
+                            pageFullscreen = view to callback
+                            CarFullscreen.enter()
+                        }
+
+                        override fun onHideCustomView() {
+                            if (pageFullscreen == null) return
+                            pageFullscreen = null
+                            if (videoMadeFullscreen) CarFullscreen.exit()
+                        }
+                    }
                     addJavascriptInterface(
                         FieldFocusBridge(onFocus = { fieldText = it }, onBlur = { fieldText = null }),
                         "GearslipField",
@@ -85,6 +129,22 @@ fun WebApp(content: String) {
             update = { it.settings.isAlgorithmicDarkeningAllowed = darkOutside },
             onRelease = { it.destroy() },
         )
+        pageFullscreen?.let { (view, _) ->
+            androidx.compose.runtime.key(view) {
+                AndroidView(
+                    factory = { context ->
+                        FrameLayout(context).apply {
+                            setBackgroundColor(android.graphics.Color.BLACK)
+                            (view.parent as? ViewGroup)?.removeView(view)
+                            addView(view, FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT))
+                        }
+                    },
+                    modifier = Modifier.fillMaxSize(),
+                    onRelease = { it.removeAllViews() },
+                )
+            }
+        }
+        }
         fieldText?.let { text ->
             CarKeyboard(
                 text = text,

gearslip/src/main/java/app/seb3thehacker/gearslip/host/CarAppConnection.kt

@@ -91,6 +91,9 @@ class CarAppConnection(private val context: Context) {
     private var navigationManager: INavigationManager? = null
     /** Main thread only, both of these - the handoff is a race between them either way round. */
     private var surfaceCallback: ISurfaceCallback? = null
+
+    /** Last visible and stable areas the UI reported, kept for the next surface. */
+    private var areas: Pair<Rect, Rect>? = null
     private var lent: Lent? = null
 
     private var binding: ServiceConnection? = null
@@ -223,6 +226,7 @@ class CarAppConnection(private val context: Context) {
     fun disconnect() = disconnect(keepLocation = false)
 
     private fun disconnect(keepLocation: Boolean) {
+        main.removeCallbacks(handshakeTimeout)
         clearToasts()
         lent?.let { sendSurfaceDestroyed(it) }
         lent = null
@@ -254,11 +258,24 @@ class CarAppConnection(private val context: Context) {
 
     // --- handshake ---------------------------------------------------------------------
 
+    /**
+     * An app that won't have Gearslip as its host never answers the first question. Car App
+     * Library 1.9 and later throw inside the app when a host that isn't Google's asks, and since
+     * the call is one-way the error never comes back, so without this the car would show
+     * "Starting..." for ever.
+     */
+    private val handshakeTimeout = Runnable {
+        if (_status.value.phase == Phase.HANDSHAKE) {
+            fail(Phase.REJECTED, "It didn't answer Gearslip. Apps built for newer versions of Android Auto only run on Google's.")
+        }
+    }
+
     private fun onBound(service: IBinder) {
         val app = ICarApp.Stub.asInterface(service)
         carApp = app
         update { it.copy(phase = Phase.HANDSHAKE, detail = "bound, asking for app info") }
         GearslipLog.i("host: bound; requesting app info")
+        main.postDelayed(handshakeTimeout, HANDSHAKE_TIMEOUT_MS)
 
         call("getAppInfo", onValue = { value ->
             val info = value as? AppInfo ?: return@call fail(Phase.FAILED, "app info was ${value?.javaClass?.simpleName}")
@@ -271,6 +288,7 @@ class CarAppConnection(private val context: Context) {
      * offers cannot be rendered correctly, so it is refused here rather than half-drawn.
      */
     private fun onAppInfo(info: AppInfo) {
+        main.removeCallbacks(handshakeTimeout)
         val negotiated = minOf(HOST_API_LEVEL, info.latestCarAppApiLevel)
         GearslipLog.i(
             "host: app api ${info.minCarAppApiLevel}..${info.latestCarAppApiLevel} " +
@@ -552,9 +570,11 @@ class CarAppConnection(private val context: Context) {
         // The app draws for the whole surface; the visible area is what isn't covered by host
         // chrome, and the stable area is the part that never gets covered. Both depend on the
         // template (see visibleAreaFor) and are reported by the UI via [reportAreas] once it
-        // has measured. Until then the whole surface is fair game.
+        // has measured. A fresh surface the same size keeps the last ones, since the UI only
+        // reports again when they change; until then the whole surface is fair game.
         val whole = Rect(0, 0, surface.width, surface.height)
-        reportAreas(whole, whole)
+        val last = areas?.takeIf { (visible, stable) -> whole.contains(visible) && whole.contains(stable) }
+        reportAreas(last?.first ?: whole, last?.second ?: whole)
 
         GearslipLog.i(
             "host: lent the app a ${surface.width}x${surface.height} @${surface.dpi}dpi surface"
@@ -575,6 +595,7 @@ class CarAppConnection(private val context: Context) {
 
     /** Tells the app which part of its surface the driver can actually see. */
     fun reportAreas(visible: Rect, stable: Rect) {
+        areas = visible to stable
         val callback = surfaceCallback ?: return
         runCatching { callback.onStableAreaChanged(stable, noop("onStableAreaChanged")) }
         runCatching { callback.onVisibleAreaChanged(visible, noop("onVisibleAreaChanged")) }
@@ -833,6 +854,9 @@ class CarAppConnection(private val context: Context) {
         /** How long a new destination waits for the old route to end; see [navigateTo]. */
         const val REROUTE_WAIT_MS = 1_500L
 
+        /** How long an app gets to answer the first question before it counts as refusing. */
+        const val HANDSHAKE_TIMEOUT_MS = 10_000L
+
         /** Context.BIND_FOREGROUND_SERVICE; the constant itself is hidden from the SDK. */
         const val BIND_FOREGROUND_SERVICE = 0x04000000
     }

gearslip/src/main/java/app/seb3thehacker/gearslip/media/CarMediaStatus.kt

@@ -31,7 +31,7 @@ class CarMediaStatus(
     fun onMessage(messageId: Int, body: ByteArray) {
         when (messageId) {
             MSG_CHANNEL_OPEN_RESPONSE -> {
-                val status = Protobuf.readInt32Field(body, 1) ?: 0
+                val status = Protobuf.readInt32Field(body, 1)
                 GearslipLog.i("media status: <- ChannelOpenResponse: status=$status")
                 if (status == 0) start()
             }

gearslip/src/main/java/app/seb3thehacker/gearslip/protocol/InputProtocol.kt

@@ -0,0 +1,36 @@
+package app.seb3thehacker.gearslip.protocol
+
+import app.seb3thehacker.gearslip.TouchPoint
+import app.seb3thehacker.gearslip.Wire
+
+/** Decodes the touch coordinates and pointer index carried by an InputReport. */
+internal object InputProtocol {
+    data class Touch(val action: Int, val actionIndex: Int, val points: List<TouchPoint>)
+
+    /** [shiftX] and [shiftY] move each point by the margin the car crops off before measuring. */
+    fun touch(body: ByteArray, size: Pair<Int, Int>?, shiftX: Int = 0, shiftY: Int = 0): Touch? {
+        val fields = Wire.fields(body)
+        val action = Wire.varint(fields, 3)?.toInt() ?: 0
+        if (action !in setOf(0, 1, 2, 5, 6)) return null
+        val pointers = Wire.allBytes(fields, 1)
+        if (pointers.isEmpty() || pointers.size > 32) return null
+        val actionIndex = Wire.varint(fields, 2)?.toInt() ?: 0
+        if (actionIndex !in pointers.indices) return null
+        val points = pointers.map { pointer ->
+            val values = Wire.fields(pointer)
+            val x = Wire.varint(values, 1)?.toInt() ?: return null
+            val y = Wire.varint(values, 2)?.toInt() ?: return null
+            val id = Wire.varint(values, 3) ?: return null
+            if (id !in 0L..31L) return null
+            TouchPoint(id.toInt(), clamp(x + shiftX, size?.first), clamp(y + shiftY, size?.second))
+        }
+        if (points.map { it.id }.toSet().size != points.size) return null
+        return Touch(action, actionIndex, points)
+    }
+
+    private fun clamp(value: Int, limit: Int?): Float = when {
+        limit == null -> value.toFloat()
+        limit <= 0 -> 0f
+        else -> value.coerceIn(0, limit - 1).toFloat()
+    }
+}

gearslip/src/main/java/app/seb3thehacker/gearslip/stats/UsageStats.kt

@@ -251,6 +251,17 @@ object UsageStats {
         if (c.phone) put("phone", "${Build.MANUFACTURER} ${Build.MODEL}")
     }
 
+    private var signerCache: String? = null
+
+    /** The first 16 hex digits of the SHA-256 of this APK's signing certificate. */
+    private fun signer(context: Context): String = signerCache ?: runCatching {
+        val cert = context.packageManager
+            .getPackageInfo(context.packageName, android.content.pm.PackageManager.GET_SIGNING_CERTIFICATES)
+            .signingInfo?.apkContentsSigners?.firstOrNull()?.toByteArray() ?: return@runCatching ""
+        java.security.MessageDigest.getInstance("SHA-256").digest(cert)
+            .take(8).joinToString("") { "%02x".format(it) }
+    }.getOrDefault("").also { signerCache = it }
+
     /**
      * What a note carries. With [everything], every field the driver shares, as Settings shows it;
      * otherwise exactly what the next note would send, which leaves out unchanged phone details.
@@ -263,6 +274,9 @@ object UsageStats {
             .put("version", BuildConfig.VERSION_NAME)
             .put("code", BuildConfig.VERSION_CODE)
             .put("build", if (BuildConfig.DEBUG) "debug" else "release")
+            // Who signed this copy, so a fork's builds can be told from Gearslip's own. Every copy
+            // from the same publisher sends the same value, so it says nothing about the phone.
+            .put("signer", signer(context))
             // Which boxes are ticked, so the server knows what this phone shares and can drop
             // anything it kept from a box since unticked.
             .put("shares", JSONArray().apply {

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/AboutLinks.kt

@@ -45,6 +45,9 @@ internal object GearslipLinks {
     const val SOURCE = "https://github.com/twinksoftware/gearslip"
     const val CARS = "$SOURCE/blob/main/CARS.md"
 
+    /** This version's release notes on GitHub; every release is tagged v plus its version name. */
+    val RELEASE_NOTES = "$SOURCE/releases/tag/v${app.seb3thehacker.gearslip.BuildConfig.VERSION_NAME}"
+
     fun open(context: Context, url: String) {
         runCatching {
             context.startActivity(Intent(Intent.ACTION_VIEW, Uri.parse(url)).addFlags(Intent.FLAG_ACTIVITY_NEW_TASK))

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/CarPreviewScreen.kt

@@ -4,15 +4,8 @@ import android.app.Activity
 import android.content.Context
 import android.content.ContextWrapper
 import android.content.res.Configuration
-import android.graphics.Bitmap
-import android.graphics.PixelFormat
-import android.hardware.HardwareBuffer
-import android.media.ImageReader
-import android.os.Handler
-import android.os.Looper
 import android.view.MotionEvent
 import androidx.activity.compose.BackHandler
-import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.BoxScope
@@ -39,9 +32,7 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.graphics.asImageBitmap
 import androidx.compose.ui.input.pointer.pointerInteropFilter
-import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.platform.LocalConfiguration
 import androidx.compose.ui.platform.LocalContext
@@ -59,7 +50,7 @@ import app.seb3thehacker.gearslip.car.CarUi
  * Runs the real car UI on the bench and shows it on the phone.
  *
  * This is the same pipeline the car gets - a VirtualDisplay hosting a Presentation, driven by
- * the same [ScreenProjector] and fed the same touches - with an ImageReader standing in for the
+ * the same [ScreenProjector] and fed the same touches - with a SurfaceView standing in for the
  * H.264 encoder. That matters for anything composited rather than drawn by Compose, such as the
  * SurfaceView a templated app draws its map into: if it appears here, it will reach the car.
  *
@@ -69,49 +60,26 @@ import app.seb3thehacker.gearslip.car.CarUi
 fun CarPreviewScreen(onBack: () -> Unit) {
     val context = LocalContext.current
     val frame by CarEnvironment.frame.collectAsStateWithLifecycle()
-    var bitmap by remember { mutableStateOf<Bitmap?>(null) }
     var viewSize by remember { mutableStateOf(0 to 0) }
     // Tied to how the phone itself is held, not a button: turn it sideways and the preview goes
     // fullscreen, turn it back and the phone's own chrome (the Back/title above the frame) returns.
     val fullscreen = LocalConfiguration.current.orientation == Configuration.ORIENTATION_LANDSCAPE
 
-    val width = frame.width
-    val height = frame.height
-    val density = frame.densityDpi
+    val previewSize by app.seb3thehacker.gearslip.car.CarSettings.previewSize.collectAsStateWithLifecycle()
+    val custom by app.seb3thehacker.gearslip.car.CarSettings.previewCustom.collectAsStateWithLifecycle()
+    val (width, height, density) = previewFrame(context, frame, previewSize, custom)
 
     val projector = remember { ScreenProjector(context) }
 
     DisposableEffect(width, height, density) {
         CarEnvironment.start(context)
-
-        // COMPOSER_OVERLAY is what makes SurfaceFlinger willing to composite into this reader;
-        // CPU_READ_OFTEN is what makes the resulting buffer lockable, which is how the frame
-        // gets copied into a Bitmap. Without both, frames arrive but every copy fails.
-        val reader = ImageReader.newInstance(
-            width, height, PixelFormat.RGBA_8888, 3,
-            HardwareBuffer.USAGE_COMPOSER_OVERLAY or
-                HardwareBuffer.USAGE_GPU_SAMPLED_IMAGE or
-                HardwareBuffer.USAGE_CPU_READ_OFTEN,
-        )
-        val handler = Handler(Looper.getMainLooper())
-        reader.setOnImageAvailableListener({ source ->
-            val image = runCatching { source.acquireLatestImage() }.getOrNull() ?: return@setOnImageAvailableListener
-            try {
-                bitmap = image.toBitmap(width, height)
-            } catch (t: Throwable) {
-                GearslipLog.e("preview: could not copy a frame", t)
-            } finally {
-                image.close()
-            }
-        }, handler)
-
-        projector.start(reader.surface, width, height, density, name = "gearslip-preview") { CarUi() }
-
-        onDispose {
-            projector.stop()
-            reader.close()
-            bitmap = null
+        // No surface yet: the SurfaceView below hands its own over once it exists, and the
+        // display draws straight into it. Copying each frame into a Bitmap instead cost two
+        // full-size allocations per frame on the main thread, and taps lagged with the size.
+        projector.start(null, width, height, density, name = "gearslip-preview") {
+            androidx.compose.runtime.CompositionLocalProvider(app.seb3thehacker.gearslip.car.LocalCarPreview provides true) { CarUi() }
         }
+        onDispose { projector.stop() }
     }
 
     // The frame is drawn the same way in both layouts; only what surrounds it differs.
@@ -140,19 +108,32 @@ fun CarPreviewScreen(onBack: () -> Unit) {
                 },
             contentAlignment = Alignment.Center,
         ) {
-            bitmap?.let {
-                Image(
-                    it.asImageBitmap(),
-                    contentDescription = "Car screen",
+            androidx.compose.runtime.key(width, height) {
+                androidx.compose.ui.viewinterop.AndroidView(
+                    factory = { viewContext ->
+                        android.view.SurfaceView(viewContext).apply {
+                            // The car's own size; the compositor scales it to the view.
+                            holder.setFixedSize(width, height)
+                            holder.addCallback(object : android.view.SurfaceHolder.Callback {
+                                override fun surfaceCreated(holder: android.view.SurfaceHolder) =
+                                    projector.setSurface(holder.surface)
+
+                                override fun surfaceChanged(holder: android.view.SurfaceHolder, format: Int, w: Int, h: Int) =
+                                    projector.setSurface(holder.surface)
+
+                                override fun surfaceDestroyed(holder: android.view.SurfaceHolder) =
+                                    projector.setSurface(null)
+                            })
+                        }
+                    },
                     modifier = Modifier.fillMaxSize(),
-                    contentScale = ContentScale.Fit,
                 )
-            } ?: Text("Waiting for a frame…", color = Color.White)
+            }
         }
     }
 
     if (fullscreen) {
-        Fullscreen(onBack) {
+        Fullscreen(width.toFloat() / height, onBack) {
             // No fillMax here: left to the bounds alone, aspectRatio takes the whole width or the
             // whole height, whichever the car's shape allows, and the rest stays black.
             frameContent(Modifier)
@@ -192,6 +173,7 @@ fun CarPreviewScreen(onBack: () -> Unit) {
  */
 @Composable
 private fun Fullscreen(
+    aspect: Float,
     onBack: () -> Unit,
     content: @Composable BoxScope.() -> Unit,
 ) {
@@ -213,19 +195,31 @@ private fun Fullscreen(
     // is on and turning it sideways/back isn't an option.
     BackHandler(onBack = onBack)
 
-    Box(
+    androidx.compose.foundation.layout.BoxWithConstraints(
         Modifier.fillMaxSize().background(Color.Black),
         contentAlignment = Alignment.Center,
     ) {
         content()
 
         // The frame swallows every touch inside it, so leaving needs either the back gesture or
-        // a button of its own. This one sits in the corner the car UI leaves emptiest.
-        FilledTonalIconButton(
-            onClick = onBack,
-            modifier = Modifier.align(Alignment.BottomStart).padding(8.dp),
-        ) {
-            Icon(Icons.Filled.Close, contentDescription = "Leave the car preview")
+        // a button of its own. The button goes in the black beside the frame, never on it: over
+        // the frame it covered the car's own buttons. A frame the screen's own shape leaves no
+        // room, and then the back gesture is the way out.
+        val frameWidth = minOf(maxWidth, maxHeight * aspect)
+        val frameHeight = minOf(maxHeight, maxWidth / aspect)
+        val room = 56.dp
+        val corner = when {
+            maxWidth - frameWidth >= room * 2 -> Alignment.BottomStart
+            maxHeight - frameHeight >= room * 2 -> Alignment.TopStart
+            else -> null
+        }
+        if (corner != null) {
+            FilledTonalIconButton(
+                onClick = onBack,
+                modifier = Modifier.align(corner).padding(8.dp),
+            ) {
+                Icon(Icons.Filled.Close, contentDescription = "Leave the car preview")
+            }
         }
     }
 }
@@ -250,14 +244,26 @@ private fun Int.toCarAction(): Int = when (this) {
  * Copies one frame out of the reader. The reader's rows are padded to a hardware-friendly
  * stride, so the copy is made at the padded width and then cropped back.
  */
-private fun android.media.Image.toBitmap(width: Int, height: Int): Bitmap {
-    val plane = planes[0]
-    val pixelStride = plane.pixelStride
-    val rowPadding = plane.rowStride - pixelStride * width
-    val padded = Bitmap.createBitmap(
-        width + rowPadding / pixelStride, height, Bitmap.Config.ARGB_8888,
-    )
-    padded.copyPixelsFromBuffer(plane.buffer)
-    return if (padded.width == width) padded
-    else Bitmap.createBitmap(padded, 0, 0, width, height).also { padded.recycle() }
+/**
+ * The size the preview draws at. The last car's frame by default; this device's whole screen,
+ * for a head unit running Gearslip on its own (issue #12); or a size typed into Settings. The
+ * two new ones get a car-like density: 160dpi for every 480 pixels of height.
+ */
+private fun previewFrame(
+    context: android.content.Context,
+    lastCar: CarEnvironment.Frame,
+    size: app.seb3thehacker.gearslip.car.PreviewSize,
+    custom: app.seb3thehacker.gearslip.car.ScreenSize?,
+): Triple<Int, Int, Int> {
+    fun carLike(w: Int, h: Int) = Triple(w, h, (160 * h / 480).coerceIn(120, 640))
+    return when (size) {
+        app.seb3thehacker.gearslip.car.PreviewSize.LAST_CAR -> Triple(lastCar.width, lastCar.height, lastCar.densityDpi)
+        app.seb3thehacker.gearslip.car.PreviewSize.CUSTOM ->
+            custom?.let { carLike(it.width, it.height) } ?: Triple(lastCar.width, lastCar.height, lastCar.densityDpi)
+        app.seb3thehacker.gearslip.car.PreviewSize.FILL -> {
+            val bounds = context.getSystemService(android.view.WindowManager::class.java).maximumWindowMetrics.bounds
+            // Landscape, whichever way the device is held right now.
+            carLike(maxOf(bounds.width(), bounds.height()) / 2 * 2, minOf(bounds.width(), bounds.height()) / 2 * 2)
+        }
+    }
 }

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/CarScreenSettings.kt

@@ -0,0 +1,158 @@
+package app.seb3thehacker.gearslip.ui
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.selection.selectable
+import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.RadioButton
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.semantics.Role
+import androidx.compose.ui.text.input.KeyboardType
+import androidx.compose.ui.unit.dp
+import app.seb3thehacker.gearslip.car.CarSettings
+import app.seb3thehacker.gearslip.car.PreviewSize
+import app.seb3thehacker.gearslip.car.ScreenFit
+import app.seb3thehacker.gearslip.car.ScreenSize
+
+/**
+ * The car screen's real size, for a head unit that reports the wrong one and stretches the
+ * picture, and the size the phone's car preview draws at. The same screen size and fit are in
+ * the car's own Settings; typing in any size is only here.
+ */
+@Composable
+internal fun CarScreenSection() {
+    val size by CarSettings.screenSize.collectAsState()
+    val fit by CarSettings.screenFit.collectAsState()
+    val preview by CarSettings.previewSize.collectAsState()
+    val previewCustom by CarSettings.previewCustom.collectAsState()
+    var editingCar by remember { mutableStateOf(false) }
+    var editingPreview by remember { mutableStateOf(false) }
+
+    if (editingCar) {
+        SizeDialog(
+            title = "Car screen size",
+            note = "Use this if the car's picture looks stretched. Enter the screen's real size, " +
+                "such as 1280x480. It takes effect the next time you connect.",
+            initial = size,
+            clearLabel = "Use the car's",
+            onDismiss = { editingCar = false },
+            onSave = { CarSettings.setScreenSize(it); editingCar = false },
+        )
+    }
+    if (editingPreview) {
+        SizeDialog(
+            title = "Preview size",
+            note = "The size the car preview draws at, such as 1920x720.",
+            initial = previewCustom,
+            clearLabel = null,
+            onDismiss = { editingPreview = false },
+            onSave = { custom ->
+                CarSettings.setPreviewSize(if (custom == null) PreviewSize.LAST_CAR else PreviewSize.CUSTOM, custom)
+                editingPreview = false
+            },
+        )
+    }
+
+    SettingsSection(
+        "Car screen",
+        footer = "Gearslip uses the size the car reports unless you set one.",
+    ) {
+        SettingsRow(
+            "Screen size",
+            Modifier.clickable { editingCar = true },
+            subtitle = size?.let { "$it, set by you" } ?: "From the car",
+        )
+        if (size != null) {
+            SettingsDivider()
+            SettingsRow(
+                "Crop the edges",
+                Modifier.selectable(fit == ScreenFit.CROP, role = Role.RadioButton) { CarSettings.setScreenFit(ScreenFit.CROP) },
+                subtitle = "For a car that cuts off the top and bottom, or the sides",
+                trailing = { RadioButton(selected = fit == ScreenFit.CROP, onClick = null) },
+            )
+            SettingsDivider()
+            SettingsRow(
+                "Squash to fit",
+                Modifier.selectable(fit == ScreenFit.SQUASH, role = Role.RadioButton) { CarSettings.setScreenFit(ScreenFit.SQUASH) },
+                subtitle = "For a car that squeezes the whole picture, so circles look like ovals",
+                trailing = { RadioButton(selected = fit == ScreenFit.SQUASH, onClick = null) },
+            )
+        }
+    }
+
+    SettingsSection("Car preview size") {
+        SettingsRow(
+            "Last car",
+            Modifier.selectable(preview == PreviewSize.LAST_CAR, role = Role.RadioButton) {
+                CarSettings.setPreviewSize(PreviewSize.LAST_CAR)
+            },
+            subtitle = "The size of the last car you connected to",
+            trailing = { RadioButton(selected = preview == PreviewSize.LAST_CAR, onClick = null) },
+        )
+        SettingsDivider()
+        SettingsRow(
+            "This screen",
+            Modifier.selectable(preview == PreviewSize.FILL, role = Role.RadioButton) {
+                CarSettings.setPreviewSize(PreviewSize.FILL)
+            },
+            subtitle = "Fills this device's screen, for a head unit running Gearslip itself",
+            trailing = { RadioButton(selected = preview == PreviewSize.FILL, onClick = null) },
+        )
+        SettingsDivider()
+        SettingsRow(
+            "Custom",
+            Modifier.selectable(preview == PreviewSize.CUSTOM, role = Role.RadioButton) {
+                if (previewCustom == null) editingPreview = true else CarSettings.setPreviewSize(PreviewSize.CUSTOM)
+            },
+            subtitle = previewCustom?.toString() ?: "Enter a size",
+            trailing = { RadioButton(selected = preview == PreviewSize.CUSTOM, onClick = null) },
+        )
+        if (preview == PreviewSize.CUSTOM) {
+            SettingsDivider()
+            SettingsRow("Change the custom size", Modifier.clickable { editingPreview = true })
+        }
+    }
+}
+
+/** Asks for a width and height; [clearLabel], when given, offers going back to no size at all. */
+@Composable
+private fun SizeDialog(
+    title: String,
+    note: String,
+    initial: ScreenSize?,
+    clearLabel: String?,
+    onDismiss: () -> Unit,
+    onSave: (ScreenSize?) -> Unit,
+) {
+    var width by remember { mutableStateOf(initial?.width?.toString().orEmpty()) }
+    var height by remember { mutableStateOf(initial?.height?.toString().orEmpty()) }
+    val parsed = ScreenSize.parse("${width}x$height")
+    val number = KeyboardOptions(keyboardType = KeyboardType.Number)
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(title) },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(12.dp)) {
+                Text(note)
+                OutlinedTextField(width, { width = it.filter(Char::isDigit) }, label = { Text("Width") }, singleLine = true, keyboardOptions = number)
+                OutlinedTextField(height, { height = it.filter(Char::isDigit) }, label = { Text("Height") }, singleLine = true, keyboardOptions = number)
+            }
+        },
+        confirmButton = { TextButton(onClick = { onSave(parsed) }, enabled = parsed != null) { Text("Save") } },
+        dismissButton = {
+            if (clearLabel != null) TextButton(onClick = { onSave(null) }) { Text(clearLabel) }
+            else TextButton(onClick = onDismiss) { Text("Cancel") }
+        },
+    )
+}

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/GearslipApp.kt

@@ -108,26 +108,22 @@ fun GearslipApp(onDisconnect: () -> Unit, onRequestCallScreening: () -> Unit) {
                 Screen.INTRO -> IntroScreen(onDone = { screen = introReturn })
                 Screen.HOME -> HomeScreen(
                     onOpenSettings = { settingsAtUsageNotes = false; screen = Screen.SETTINGS },
-                    onOpenWhatsNew = { backTo = Screen.HOME; screen = Screen.WHATS_NEW },
                     onOpenHelp = { backTo = Screen.HOME; screen = Screen.HELP },
                     onOpenUsageNotes = { settingsAtUsageNotes = true; screen = Screen.SETTINGS },
+                    onOpenCarPreview = { backTo = Screen.HOME; screen = Screen.CAR_PREVIEW },
+                    onOpenLogs = { backTo = Screen.HOME; screen = Screen.LOGS },
                     onDisconnect = onDisconnect,
                 )
                 Screen.WHATS_NEW -> WhatsNewScreen(onBack = { screen = backTo })
-                Screen.LOGS -> LogsScreen(onBack = { screen = Screen.SETTINGS })
+                Screen.LOGS -> LogsScreen(onBack = { screen = backTo })
                 Screen.SETTINGS -> SettingsScreen(
                     onBack = { screen = Screen.HOME },
                     onOpenRecommendedApps = { settingsAtUsageNotes = false; screen = Screen.RECOMMENDED_APPS },
-                    onOpenWhatsNew = { settingsAtUsageNotes = false; backTo = Screen.SETTINGS; screen = Screen.WHATS_NEW },
-                    onOpenHelp = { settingsAtUsageNotes = false; backTo = Screen.SETTINGS; screen = Screen.HELP },
-                    onOpenCarPreview = { settingsAtUsageNotes = false; screen = Screen.CAR_PREVIEW },
-                    onOpenLogs = { settingsAtUsageNotes = false; screen = Screen.LOGS },
                     onReplayTutorial = { screen = Screen.SETUP_GUIDE },
-                    onReplayIntro = { Intro.replay(context); introReturn = Screen.SETTINGS; screen = Screen.INTRO },
                     atUsageNotes = settingsAtUsageNotes,
                 )
                 Screen.RECOMMENDED_APPS -> RecommendedAppsScreen(onBack = { screen = Screen.SETTINGS })
-                Screen.CAR_PREVIEW -> CarPreviewScreen(onBack = { screen = Screen.SETTINGS })
+                Screen.CAR_PREVIEW -> CarPreviewScreen(onBack = { screen = backTo })
                 Screen.HELP -> HelpScreen(
                     onBack = { screen = backTo },
                     onRequestCallScreening = onRequestCallScreening,
@@ -148,8 +144,9 @@ fun GearslipApp(onDisconnect: () -> Unit, onRequestCallScreening: () -> Unit) {
                 )
             }
         }
-        // A car keyboard is open: offer the phone's own, for a passenger.
-        if (screen != Screen.CAR_PREVIEW) PhoneTypingBar()
+        // A car keyboard is open: offer the phone's own, for a passenger. In the car preview it is
+        // the only keyboard, since the preview draws none of its own.
+        PhoneTypingBar()
     }
 }
 

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/HomeScreen.kt

@@ -5,6 +5,7 @@ import app.seb3thehacker.gearslip.speech.SpeechModels
 import androidx.compose.material3.LinearProgressIndicator
 
 import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.heightIn
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -27,6 +28,8 @@ import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.filled.KeyboardArrowRight
+import androidx.compose.material.icons.automirrored.filled.List
+import androidx.compose.material.icons.automirrored.filled.Send
 import androidx.compose.material.icons.filled.Info
 import androidx.compose.material.icons.filled.Send
 import androidx.compose.material.icons.filled.List
@@ -60,9 +63,10 @@ import app.seb3thehacker.gearslip.stats.WorkedPrompt
 @Composable
 fun HomeScreen(
     onOpenSettings: () -> Unit,
-    onOpenWhatsNew: () -> Unit,
     onOpenHelp: () -> Unit,
     onOpenUsageNotes: () -> Unit,
+    onOpenCarPreview: () -> Unit,
+    onOpenLogs: () -> Unit,
     onDisconnect: () -> Unit,
 ) {
     val status by SessionStatus.state.collectAsStateWithLifecycle()
@@ -125,21 +129,11 @@ fun HomeScreen(
 
                 // Sits at the bottom, where a thumb reaches it.
                 Column(Modifier.padding(vertical = 16.dp)) {
-                    SettingsCard {
-                        SettingsRow(
-                            "What's new in ${Intro.release}",
-                            Modifier.clickable(onClick = onOpenWhatsNew),
-                            icon = Icons.Filled.Star,
-                            trailing = { Arrow() },
-                        )
-                        SettingsDivider()
-                        SettingsRow(
-                            "Which cars work",
-                            Modifier.clickable(onClick = onOpenHelp),
-                            subtitle = "Most do. See which ones, and what to set up first",
-                            icon = Icons.Filled.Info,
-                            trailing = { Arrow() },
-                        )
+                    Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                        HomeShortcut(Icons.Filled.Info, "Help", onOpenHelp, Modifier.weight(1f))
+                        // The preview draws the car screen on the phone, so it waits until no car is using it.
+                        if (!live) HomeShortcut(Icons.Filled.PlayArrow, "Preview", onOpenCarPreview, Modifier.weight(1f))
+                        HomeShortcut(Icons.AutoMirrored.Filled.List, "Logs", onOpenLogs, Modifier.weight(1f))
                     }
                     if (live) {
                         Spacer(Modifier.height(16.dp))
@@ -157,6 +151,27 @@ fun HomeScreen(
     }
 }
 
+/** One of Home's shortcuts at the bottom: an icon over a one-word label, small enough that all fit in a row. */
+@Composable
+private fun HomeShortcut(icon: androidx.compose.ui.graphics.vector.ImageVector, label: String, onClick: () -> Unit, modifier: Modifier = Modifier) {
+    Surface(
+        onClick = onClick,
+        modifier = modifier.heightIn(min = 64.dp),
+        shape = MaterialTheme.shapes.large,
+        color = MaterialTheme.colorScheme.secondaryContainer,
+        contentColor = MaterialTheme.colorScheme.onSecondaryContainer,
+    ) {
+        Column(
+            Modifier.padding(vertical = 10.dp, horizontal = 4.dp),
+            horizontalAlignment = Alignment.CenterHorizontally,
+            verticalArrangement = Arrangement.spacedBy(4.dp),
+        ) {
+            Icon(icon, contentDescription = null, modifier = Modifier.size(22.dp))
+            Text(label, style = MaterialTheme.typography.labelMedium, maxLines = 1)
+        }
+    }
+}
+
 /** Bluetooth audio is chosen, but the phone isn't connected to the car. See [BluetoothAudioCheck]. */
 @Composable
 private fun BluetoothMissingCard() {

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/IntroScreen.kt

@@ -135,11 +135,6 @@ object Intro {
             .apply()
     }
 
-    /** A replay from Settings starts at the first page. */
-    fun replay(context: Context) {
-        context.getSharedPreferences(PREFS, Context.MODE_PRIVATE).edit().remove(KEY_STEP).apply()
-    }
-
     /** The page the intro was on, so an app restart part-way through resumes there. */
     internal fun savedStep(context: Context): String? =
         context.getSharedPreferences(PREFS, Context.MODE_PRIVATE).getString(KEY_STEP, null)

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/LogsScreen.kt

@@ -8,6 +8,7 @@ import androidx.compose.foundation.layout.navigationBarsPadding
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.fillMaxSize
@@ -55,6 +56,9 @@ fun LogsScreen(onBack: () -> Unit) {
     val version by GearslipLog.version.collectAsStateWithLifecycle()
     val lines = remember(version) { GearslipLog.snapshot() }
 
+    var pastOpen by remember { mutableStateOf(false) }
+    if (pastOpen) PastLogsDialog(onDismiss = { pastOpen = false })
+
     val listState = rememberLazyListState()
     val atEnd by remember {
         derivedStateOf {
@@ -96,17 +100,16 @@ fun LogsScreen(onBack: () -> Unit) {
                     Button(
                         onClick = {
                             scope.launch {
-                            val uri = withContext(Dispatchers.IO) { GearslipLog.shareableFile(context) }
-                            val send = Intent(Intent.ACTION_SEND)
-                                .setType("text/plain")
-                                .putExtra(Intent.EXTRA_SUBJECT, "Gearslip log")
-                                .putExtra(Intent.EXTRA_STREAM, uri)
-                                .addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
-                            context.startActivity(Intent.createChooser(send, "Share log"))
-                        }
+                                val uri = withContext(Dispatchers.IO) { GearslipLog.shareableFile(context) }
+                                shareLog(context, uri)
+                            }
                         },
                         modifier = Modifier.weight(1f).height(56.dp),
                     ) { Text("Share") }
+                    OutlinedButton(
+                        onClick = { pastOpen = true },
+                        modifier = Modifier.weight(1f).height(56.dp),
+                    ) { Text("Earlier") }
                     OutlinedButton(
                         onClick = { GearslipLog.clearLive() },
                         modifier = Modifier.weight(1f).height(56.dp),
@@ -153,6 +156,68 @@ fun LogsScreen(onBack: () -> Unit) {
     }
 }
 
+private fun shareLog(context: android.content.Context, uri: android.net.Uri) {
+    val send = Intent(Intent.ACTION_SEND)
+        .setType("text/plain")
+        .putExtra(Intent.EXTRA_SUBJECT, "Gearslip log")
+        .putExtra(Intent.EXTRA_STREAM, uri)
+        .addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+    context.startActivity(Intent.createChooser(send, "Share log"))
+}
+
+/**
+ * Logs from earlier launches. Opening the app after a crash starts a new log, so the one that
+ * saw the crash is only reachable here.
+ */
+@Composable
+private fun PastLogsDialog(onDismiss: () -> Unit) {
+    val context = LocalContext.current
+    val scope = rememberCoroutineScope()
+    val logs by androidx.compose.runtime.produceState<List<GearslipLog.PastLog>?>(null) {
+        value = withContext(Dispatchers.IO) { GearslipLog.pastLogs(context) }
+    }
+    val format = remember { java.text.SimpleDateFormat("EEE d MMM, h:mm a", java.util.Locale.getDefault()) }
+    androidx.compose.material3.AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text("Earlier logs") },
+        text = {
+            val list = logs
+            when {
+                list == null -> Text("Loading…")
+                list.isEmpty() -> Text("No earlier logs yet. Each time Gearslip starts, it begins a new one.")
+                else -> LazyColumn {
+                    itemsIndexed(list) { _, log ->
+                        androidx.compose.foundation.layout.Column(
+                            Modifier
+                                .fillMaxWidth()
+                                .clickable {
+                                    scope.launch {
+                                        val uri = withContext(Dispatchers.IO) { GearslipLog.shareableFile(context, log.file) }
+                                        shareLog(context, uri)
+                                    }
+                                }
+                                .padding(vertical = 12.dp),
+                        ) {
+                            Text(log.started?.let(format::format) ?: log.file.name, style = MaterialTheme.typography.titleMedium)
+                            val detail = listOfNotNull(
+                                "Crashed".takeIf { log.crashed },
+                                log.car,
+                                "${(log.file.length() + 1023) / 1024} KB",
+                            ).joinToString(" · ")
+                            Text(
+                                detail,
+                                style = MaterialTheme.typography.bodyMedium,
+                                color = if (log.crashed) MaterialTheme.colorScheme.error else MaterialTheme.colorScheme.onSurfaceVariant,
+                            )
+                        }
+                    }
+                }
+            }
+        },
+        confirmButton = { androidx.compose.material3.TextButton(onClick = onDismiss) { Text("Close") } },
+    )
+}
+
 /** Lines look like "HH:mm:ss.SSS L message"; the level letter sits at index 13. */
 @Composable
 private fun colorFor(line: String): Color = when (line.getOrNull(13)) {

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/SettingsScreen.kt

@@ -79,12 +79,7 @@ import kotlinx.coroutines.withContext
 fun SettingsScreen(
     onBack: () -> Unit,
     onOpenRecommendedApps: () -> Unit,
-    onOpenWhatsNew: () -> Unit,
-    onOpenHelp: () -> Unit,
-    onOpenCarPreview: () -> Unit,
-    onOpenLogs: () -> Unit,
     onReplayTutorial: () -> Unit,
-    onReplayIntro: () -> Unit,
     atUsageNotes: Boolean = false,
 ) {
     val scroll = rememberScrollState()
@@ -119,13 +114,23 @@ fun SettingsScreen(
             verticalArrangement = Arrangement.spacedBy(24.dp),
         ) {
             Spacer(Modifier.height(0.dp))
+            SettingsSection {
+                val context = LocalContext.current
+                SettingsRow(
+                    "What's new",
+                    Modifier.clickable { GearslipLinks.open(context, GearslipLinks.RELEASE_NOTES) },
+                    subtitle = "Read the ${BuildConfig.VERSION_NAME} release notes on GitHub",
+                    icon = Icons.Filled.Star,
+                    trailing = { Arrow() },
+                )
+            }
             SettingsSection(
                 "Support Gearslip",
                 footer = "Gearslip is free, with no ads and no tracking. Your support keeps it going.",
             ) { DonateRows() }
             ConnectionSection()
-            HelpSection(onOpenHelp, onOpenCarPreview, onOpenLogs)
             CarAudioSection()
+            CarScreenSection()
             VoiceModelSection()
             if (SHOW_RECOMMENDED_APPS) AppsSection(onOpenRecommendedApps)
             SettingsSection(
@@ -135,7 +140,8 @@ fun SettingsScreen(
             ) { UsageStatsRows() }
             SettingsSection("Updates") { UpdateRow() }
             CertificateSection()
-            AboutSection(onOpenWhatsNew, onReplayTutorial, onReplayIntro)
+            AboutSection(onReplayTutorial)
+            if (BuildConfig.DEBUG) DebugSection()
             Spacer(Modifier.height(16.dp))
         }
     }
@@ -148,26 +154,10 @@ private fun Arrow() = Icon(
     tint = MaterialTheme.colorScheme.onSurfaceVariant,
 )
 
-/** What's new, the replays, and where Gearslip lives outside the app. */
+/** The setup guide replay, and where Gearslip lives outside the app. */
 @Composable
-private fun AboutSection(onOpenWhatsNew: () -> Unit, onReplayTutorial: () -> Unit, onReplayIntro: () -> Unit) {
+private fun AboutSection(onReplayTutorial: () -> Unit) {
     SettingsSection("About") {
-        SettingsRow(
-            "What's new",
-            Modifier.clickable(onClick = onOpenWhatsNew),
-            subtitle = "Version ${BuildConfig.VERSION_NAME}",
-            icon = Icons.Filled.Star,
-            trailing = { Arrow() },
-        )
-        SettingsDivider()
-        SettingsRow(
-            "Replay the ${Intro.release} intro",
-            Modifier.clickable(onClick = onReplayIntro),
-            subtitle = "What's in this release, in a few taps",
-            icon = Icons.Filled.Star,
-            trailing = { Arrow() },
-        )
-        SettingsDivider()
         SettingsRow(
             "Replay the setup guide",
             Modifier.clickable(onClick = onReplayTutorial),
@@ -199,48 +189,17 @@ private fun ConnectionSection() {
     }
 }
 
-/** Connection help, and the tools for checking what Gearslip does. */
+/** Tools for testing a debug build; release builds never show this section. */
 @Composable
-private fun HelpSection(onOpenHelp: () -> Unit, onOpenCarPreview: () -> Unit, onOpenLogs: () -> Unit) {
+private fun DebugSection() {
     val context = LocalContext.current
-    val status by SessionStatus.state.collectAsState()
-    val live = status.phase == SessionStatus.Phase.CONNECTING || status.phase == SessionStatus.Phase.PROJECTING
-    SettingsSection("Help and tools") {
+    SettingsSection("Debug build") {
         SettingsRow(
-            "Connection help",
-            Modifier.clickable(onClick = onOpenHelp),
-            subtitle = "Which cars work, and what to set up first",
-            icon = Icons.Filled.Info,
-            trailing = { Arrow() },
+            "Send a test message",
+            Modifier.clickable { TestMessage.post(context) },
+            subtitle = "Posts a message notification to read on the car",
+            icon = Icons.AutoMirrored.Filled.Send,
         )
-        // The preview draws the car screen on the phone, so it waits until no car is using it.
-        if (!live) {
-            SettingsDivider()
-            SettingsRow(
-                "Car preview",
-                Modifier.clickable(onClick = onOpenCarPreview),
-                subtitle = "See the car screen on your phone",
-                icon = Icons.Filled.PlayArrow,
-                trailing = { Arrow() },
-            )
-        }
-        SettingsDivider()
-        SettingsRow(
-            "Live logs",
-            Modifier.clickable(onClick = onOpenLogs),
-            subtitle = "What Gearslip and the car are saying to each other",
-            icon = Icons.AutoMirrored.Filled.List,
-            trailing = { Arrow() },
-        )
-        if (BuildConfig.DEBUG) {
-            SettingsDivider()
-            SettingsRow(
-                "Send a test message",
-                Modifier.clickable { TestMessage.post(context) },
-                subtitle = "Debug builds only. Posts a message notification to read on the car",
-                icon = Icons.AutoMirrored.Filled.Send,
-            )
-        }
     }
 }
 

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/WirelessButton.kt

@@ -109,6 +109,8 @@ internal fun WirelessButton() {
                                 .clickable {
                                     devices = null
                                     WirelessLink.start(context, device)
+                                    // Next time this car connects, Gearslip does this by itself.
+                                    app.seb3thehacker.gearslip.wireless.WirelessAuto.connectedByHand(context, device)
                                 }
                                 .padding(vertical = 14.dp),
                         )

gearslip/src/main/java/app/seb3thehacker/gearslip/wireless/CarPresenceService.kt

@@ -0,0 +1,15 @@
+package app.seb3thehacker.gearslip.wireless
+
+import android.companion.CompanionDeviceService
+
+/** Android calls this when a car approved in [WirelessAuto] connects over Bluetooth. */
+class CarPresenceService : CompanionDeviceService() {
+
+    @Deprecated("Deprecated in Java")
+    override fun onDeviceAppeared(address: String) {
+        WirelessAuto.carAppeared(applicationContext, address)
+    }
+
+    @Deprecated("Deprecated in Java")
+    override fun onDeviceDisappeared(address: String) {}
+}

gearslip/src/main/java/app/seb3thehacker/gearslip/wireless/WirelessAuto.kt

@@ -0,0 +1,116 @@
+package app.seb3thehacker.gearslip.wireless
+
+import android.annotation.SuppressLint
+import android.bluetooth.BluetoothDevice
+import android.companion.AssociationRequest
+import android.companion.BluetoothDeviceFilter
+import android.companion.CompanionDeviceManager
+import android.content.Context
+import android.content.Intent
+import android.content.IntentSender
+import android.os.Handler
+import android.os.Looper
+import app.seb3thehacker.gearslip.GearslipLog
+import app.seb3thehacker.gearslip.GearslipActivity
+
+/**
+ * Starts wireless Android Auto by itself when a car Gearslip has connected to before comes up
+ * over Bluetooth.
+ *
+ * Android only lets an app wake up and open its screen from the background for a device it
+ * manages as a companion, so the first wireless connection to a car also asks Android to make
+ * that car Gearslip's companion. Android shows its own one-time "Allow" for it; after that it
+ * tells [CarPresenceService] whenever the car connects, and Gearslip connects to it.
+ */
+object WirelessAuto {
+
+    /** Action on the activity's intent when the car came up on its own. */
+    const val ACTION_CAR_NEARBY = "app.seb3thehacker.gearslip.CAR_NEARBY"
+    const val EXTRA_ADDRESS = "address"
+
+    private const val PREFS = "gearslip_wireless_auto"
+
+    private val log = GearslipLog.tagged("AAW")
+
+    /** Set by the activity: shows Android's companion dialog, which only an activity can do. */
+    @Volatile var showApproval: ((IntentSender, String) -> Unit)? = null
+
+    /**
+     * Called whenever the driver connects to [device] by hand. Asks Android once per car; a car
+     * already approved only has its presence watched again, in case Android forgot. A car only
+     * counts as asked once the driver has answered the dialog: if it never showed, the next
+     * connection by hand asks again.
+     */
+    @SuppressLint("MissingPermission")
+    fun connectedByHand(context: Context, device: BluetoothDevice) {
+        val manager = context.getSystemService(CompanionDeviceManager::class.java) ?: return
+        val address = device.address
+        if (isCompanion(manager, address)) {
+            watch(context, address)
+            return
+        }
+        if (context.getSharedPreferences(PREFS, Context.MODE_PRIVATE).getBoolean(address, false)) {
+            log.i("auto-connect: already asked about this car and it was declined; connect by hand")
+            return
+        }
+
+        val request = AssociationRequest.Builder()
+            .addDeviceFilter(BluetoothDeviceFilter.Builder().setAddress(address).build())
+            .setSingleDevice(true)
+            .build()
+        log.i("auto-connect: asking Android to let Gearslip watch for ${WirelessLink.name(device)}")
+        @Suppress("DEPRECATION")
+        manager.associate(request, object : CompanionDeviceManager.Callback() {
+            @Deprecated("Deprecated in Java")
+            override fun onDeviceFound(chooser: IntentSender) {
+                showApproval?.invoke(chooser, address) ?: log.w("auto-connect: no screen to ask on")
+            }
+
+            override fun onFailure(error: CharSequence?) {
+                log.w("auto-connect: Android wouldn't ask ($error)")
+            }
+        }, Handler(Looper.getMainLooper()))
+    }
+
+    /** The driver allowed it in Android's dialog. */
+    fun approved(context: Context, address: String) {
+        log.i("auto-connect: allowed")
+        answered(context, address)
+        watch(context, address)
+    }
+
+    /** The driver said no in Android's dialog: this car isn't asked about again. */
+    fun declined(context: Context, address: String) {
+        log.w("auto-connect: declined in Android's dialog")
+        answered(context, address)
+    }
+
+    private fun answered(context: Context, address: String) {
+        context.getSharedPreferences(PREFS, Context.MODE_PRIVATE).edit().putBoolean(address, true).apply()
+    }
+
+    @SuppressLint("MissingPermission")
+    private fun watch(context: Context, address: String) {
+        val manager = context.getSystemService(CompanionDeviceManager::class.java) ?: return
+        @Suppress("DEPRECATION")
+        runCatching { manager.startObservingDevicePresence(address) }
+            .onFailure { log.w("auto-connect: couldn't watch for the car (${it.message})") }
+    }
+
+    @Suppress("DEPRECATION")
+    private fun isCompanion(manager: CompanionDeviceManager, address: String): Boolean =
+        runCatching { manager.associations.any { it.equals(address, ignoreCase = true) } }.getOrDefault(false)
+
+    /** From [CarPresenceService]: the car is here, so bring Gearslip up to connect to it. */
+    fun carAppeared(context: Context, address: String) {
+        log.i("auto-connect: a car Gearslip knows connected over Bluetooth")
+        runCatching {
+            context.startActivity(
+                Intent(context, GearslipActivity::class.java)
+                    .setAction(ACTION_CAR_NEARBY)
+                    .putExtra(EXTRA_ADDRESS, address)
+                    .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK),
+            )
+        }.onFailure { log.w("auto-connect: couldn't open Gearslip (${it.message})") }
+    }
+}

gearslip/src/main/java/app/seb3thehacker/gearslip/wireless/WirelessLink.kt

@@ -82,6 +82,9 @@ object WirelessLink {
     @Volatile private var tcp: Socket? = null
     @Volatile private var network: ConnectivityManager.NetworkCallback? = null
     @Volatile private var worker: Thread? = null
+
+    /** A start-up or a session's Bluetooth channel is under way. */
+    val busy: Boolean get() = worker?.isAlive == true
     /** Set when Android drops the car's network mid-try, so the rest don't bind to a dead one. */
     @Volatile private var lostNetwork: Network? = null
     /** Bumped on each Wi-Fi join and on stop, so an older run of TCP tries ends instead of racing the new one. */

gearslip/src/test/java/app/seb3thehacker/gearslip/ConnectionLifecycleTest.kt

@@ -1,5 +1,6 @@
 package app.seb3thehacker.gearslip
 
+import android.view.Surface
 import java.io.ByteArrayInputStream
 import java.io.ByteArrayOutputStream
 import java.io.IOException
@@ -7,17 +8,20 @@ import java.io.InputStream
 import java.nio.ByteBuffer
 import java.util.concurrent.CountDownLatch
 import java.util.concurrent.ExecutorService
+import java.util.concurrent.FutureTask
 import java.util.concurrent.TimeUnit
 import javax.net.ssl.SSLContext
+import org.junit.Assert.assertArrayEquals
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertTrue
+import org.junit.Assert.assertFalse
 import org.junit.Test
 
 class ConnectionLifecycleTest {
     private val version = message(1, byteArrayOf(0, 1, 0, 3))
 
     private fun message(id: Int, body: ByteArray = byteArrayOf()) = Frames.build(
-        Frames.CHANNEL_CONTROL, false, byteArrayOf(0, id.toByte()) + body,
+        Frames.CHANNEL_CONTROL, false, byteArrayOf((id ushr 8).toByte(), id.toByte()) + body,
     )
 
     private fun hello(): ByteArray {
@@ -41,13 +45,13 @@ class ConnectionLifecycleTest {
     private fun runner(input: InputStream) = GearslipRunner(input, ByteArrayOutputStream(), ::identity)
 
     @Test fun `rejected authentication ignores subsequent success and service discovery in the same read`() {
-        for (status in listOf(-2, -3)) {
+        for (status in listOf(-2, -3, -23, -24)) {
             runner(ByteArrayInputStream(
                 version + hello() + message(4, Protobuf.varintField(1, status.toLong())) +
                     message(4, Protobuf.varintField(1, 0)) + message(6) + version,
             )).run()
             assertEquals(
-                if (status == -2) SessionReport.Category.CERTIFICATE else SessionReport.Category.AUTH,
+                if (status == -3) SessionReport.Category.AUTH else SessionReport.Category.CERTIFICATE,
                 SessionReport.category,
             )
             assertEquals(SessionStatus.Phase.FAILED, SessionStatus.state.value.phase)
@@ -56,14 +60,70 @@ class ConnectionLifecycleTest {
         }
     }
 
+    @Test fun `protocol error terminates setup and ignores later messages`() {
+        for (error in listOf(255, 65535)) {
+            val runner = runner(ByteArrayInputStream(version + message(error) + version + message(6)))
+            runner.run()
+            assertFalse(getField(runner, "running") as Boolean)
+            assertEquals(SessionReport.Category.UNKNOWN, SessionReport.category)
+            assertEquals("Protocol error", SessionStatus.state.value.headline)
+            assertEquals(SessionReport.Stage.VERSIONS, SessionReport.stage)
+        }
+    }
+
+    @Test fun `head unit can end the session before authentication`() {
+        val output = ByteArrayOutputStream()
+        val runner = GearslipRunner(ByteArrayInputStream(version + message(15, Protobuf.varintField(1, 7))), output, ::identity)
+        runner.run()
+        val parser = Frames.Parser()
+        parser.append(output.toByteArray(), output.size())
+        assertEquals(2, requireNotNull(parser.next()).payload[1].toInt())
+        val reply = requireNotNull(parser.next())
+        assertFalse(reply.encrypted)
+        assertArrayEquals(byteArrayOf(0, 16), reply.payload)
+        assertEquals(SessionReport.Category.BYEBYE, SessionReport.category)
+        assertEquals(SessionStatus.Phase.DISCONNECTED, SessionStatus.state.value.phase)
+    }
+
     @Test fun `TLS failure ignores later protocol messages`() {
         val fatalAlert = message(3, byteArrayOf(21, 3, 3, 0, 2, 2, 42))
         runner(ByteArrayInputStream(version + hello() + fatalAlert + version + message(6))).run()
         assertEquals(SessionReport.Category.TLS, SessionReport.category)
-        assertEquals("Head unit rejected the certificate", SessionStatus.state.value.headline)
+        assertEquals("Secure connection failed", SessionStatus.state.value.headline)
         assertTrue(SessionReport.stage < SessionReport.Stage.ACCEPTED)
     }
 
+    @Test fun `local TLS failure ends the session without waiting for peer EOF`() {
+        val input = CountingInput(version + hello())
+        val runner = GearslipRunner(input, ByteArrayOutputStream(), { error("identity unavailable") })
+        runner.run()
+        assertEquals(1, input.reads)
+        assertEquals(SessionReport.Category.TLS, SessionReport.category)
+        assertEquals("Secure connection failed", SessionStatus.state.value.headline)
+        assertTrue((getField(runner, "writer") as ExecutorService).isShutdown)
+    }
+
+    @Test fun `unsupported version sends rejection and ends without waiting for peer EOF`() {
+        val input = CountingInput(message(1, byteArrayOf(0, 0, 0, 9)))
+        val output = ByteArrayOutputStream()
+        val runner = GearslipRunner(input, output, ::identity)
+        runner.run()
+        assertEquals(1, input.reads)
+        val parser = Frames.Parser()
+        parser.append(output.toByteArray(), output.size())
+        val response = requireNotNull(parser.next())
+        assertArrayEquals(byteArrayOf(0, 2) + ProtocolVersion.respond(0, 9).bytes, response.payload)
+        assertEquals("Unsupported protocol", SessionStatus.state.value.headline)
+    }
+
+    private class CountingInput(bytes: ByteArray) : ByteArrayInputStream(bytes) {
+        var reads = 0
+        override fun read(bytes: ByteArray, offset: Int, length: Int): Int {
+            reads++
+            return super.read(bytes, offset, length)
+        }
+    }
+
     @Test fun `authentication success before TLS completes is ignored`() {
         runner(ByteArrayInputStream(version + message(4, Protobuf.varintField(1, 0)))).run()
         assertEquals(SessionReport.Category.TLS, SessionReport.category)
@@ -133,4 +193,64 @@ class ConnectionLifecycleTest {
             assertTrue((field.get(runner) as ExecutorService).isShutdown)
         }
     }
+    @Test fun `ping echoes the full timestamp and optional payload`() {
+        for (payload in listOf(null, byteArrayOf(), byteArrayOf(0, -1, 42))) {
+            val output = ByteArrayOutputStream()
+            val runner = GearslipRunner(ByteArrayInputStream(byteArrayOf()), output, ::identity)
+            val identity = identity()
+            val tls = FutureTask { PhoneTls(identity.keyStore, identity.password) }.apply { run() }
+            setField(runner, "identityTask", tls)
+            val timestamp = 0x1234_5678_9abcL
+            val request = Protobuf.varintField(1, timestamp) + Protobuf.varintField(2, 1) +
+                (payload?.let { Protobuf.bytesField(3, it) } ?: byteArrayOf())
+            val ping = GearslipRunner::class.java.getDeclaredMethod("onPingRequest", ByteArray::class.java)
+                .apply { isAccessible = true }
+            try {
+                ping.invoke(runner, request)
+                val writer = getField(runner, "writer") as ExecutorService
+                writer.shutdown()
+                assertTrue(writer.awaitTermination(2, TimeUnit.SECONDS))
+                val parser = Frames.Parser()
+                parser.append(output.toByteArray(), output.size())
+                val response = requireNotNull(parser.next()).payload
+                assertEquals(12, response[1].toInt())
+                val fields = Wire.fields(response.copyOfRange(2, response.size))
+                assertEquals(timestamp, Wire.varint(fields, 1))
+                assertArrayEquals(payload, Wire.bytes(fields, 2))
+            } finally {
+                runner.stop()
+            }
+        }
+    }
+
+    private fun getField(runner: GearslipRunner, name: String): Any? =
+        GearslipRunner::class.java.getDeclaredField(name).apply { isAccessible = true }.get(runner)
+
+    private fun setField(runner: GearslipRunner, name: String, value: Any) {
+        GearslipRunner::class.java.getDeclaredField(name).apply { isAccessible = true }.set(runner, value)
+    }
+
+
+    @Test fun `touchpad reports are not injected as touchscreen taps`() {
+        var touches = 0
+        val projection = object : Projection {
+            override fun onSurfaceReady(surface: Surface, width: Int, height: Int, densityDpi: Int) = Unit
+            override fun onTouch(action: Int, actionIndex: Int, points: List<TouchPoint>) { touches++ }
+            override fun onProjectionStopped() = Unit
+        }
+        val runner = GearslipRunner(ByteArrayInputStream(byteArrayOf()), ByteArrayOutputStream(), ::identity, projection)
+        val input = GearslipRunner::class.java.getDeclaredMethod("onInputReport", ByteArray::class.java)
+            .apply { isAccessible = true }
+        val touch = Protobuf.bytesField(1, Protobuf.varintField(1, 100) +
+            Protobuf.varintField(2, 200) + Protobuf.varintField(3, 0))
+        try {
+            input.invoke(runner, Protobuf.varintField(1, 1000) + Protobuf.bytesField(7, touch))
+            assertEquals(0, touches)
+            input.invoke(runner, Protobuf.varintField(1, 1000) + Protobuf.bytesField(3, touch))
+            assertEquals(1, touches)
+        } finally {
+            runner.stop()
+        }
+    }
+
 }

gearslip/src/test/java/app/seb3thehacker/gearslip/CryptoTest.kt

@@ -1,5 +1,6 @@
 package app.seb3thehacker.gearslip
 
+import org.junit.Assert.assertFalse
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertTrue
 import org.junit.Test
@@ -42,6 +43,14 @@ class CryptoTest {
         assertTrue(TlsSelfTest.run(identity))
     }
 
+    @Test
+    fun `TLS still connects a head unit that presents no certificate, as homemade ones may`() {
+        val generated = SelfSignedCert.generate()
+        val identity = CertProvider.Identity(generated.keyStore, generated.certificate,
+            SelfSignedCert.PASSWORD, "test")
+        assertTrue(TlsSelfTest.run(identity, withClientCertificate = false))
+    }
+
     @Test
     fun `frames round-trip through the parser`() {
         val payload = ByteArray(300) { it.toByte() }

gearslip/src/test/java/app/seb3thehacker/gearslip/FramingTest.kt

@@ -0,0 +1,94 @@
+package app.seb3thehacker.gearslip
+
+import java.io.ByteArrayOutputStream
+import java.io.IOException
+import org.junit.Assert.*
+import org.junit.Test
+
+class FramingTest {
+    @Test fun `fragmentation survives every byte arriving separately`() {
+        val message = ByteArray(40_000) { it.toByte() }
+        val output = ByteArrayOutputStream()
+        assertEquals(3, Frames.writeMessage(output, 5, false, Frames.MESSAGE_SPECIFIC, message) { error("plaintext") })
+        val parser = Frames.Parser()
+        val assembler = Frames.Assembler()
+        var received: ByteArray? = null
+        for (byte in output.toByteArray()) {
+            parser.append(byteArrayOf(byte), 1)
+            parser.next()?.let { received = assembler.offer(it, it.payload) }
+        }
+        assertArrayEquals(message, received)
+    }
+
+    @Test fun `encrypted fragments count plaintext length and encrypt each chunk`() {
+        val output = ByteArrayOutputStream()
+        val message = ByteArray(20_000) { 42 }
+        Frames.writeMessage(output, 1, true, Frames.MESSAGE_SPECIFIC, message) { byteArrayOf(99) + it }
+        val parser = Frames.Parser()
+        parser.append(output.toByteArray(), output.size())
+        val first = parser.next()!!
+        val last = parser.next()!!
+        assertEquals(20_000, first.totalSize)
+        assertEquals(16_121, first.payload.size)
+        assertEquals(Frames.TYPE_LAST, last.frameType)
+        val assembler = Frames.Assembler()
+        assertNull(assembler.offer(first, first.payload.drop(1).toByteArray()))
+        assertArrayEquals(message, assembler.offer(last, last.payload.drop(1).toByteArray()))
+    }
+
+    @Test fun `fragment budget includes the short or extended header`() {
+        for (size in listOf(16_124, 16_125, 32_245)) {
+            val output = ByteArrayOutputStream()
+            Frames.writeMessage(output, 1, false, Frames.MESSAGE_SPECIFIC, ByteArray(size)) { error("plaintext") }
+            val parser = Frames.Parser()
+            parser.append(output.toByteArray(), output.size())
+            val first = parser.next()!!
+            if (size == 16_124) {
+                assertEquals(Frames.TYPE_BULK, first.frameType)
+                assertEquals(16_124, first.payload.size)
+            } else {
+                assertEquals(Frames.TYPE_FIRST, first.frameType)
+                assertEquals(size, first.totalSize)
+                assertEquals(16_120, first.payload.size)
+                val next = parser.next()!!
+                if (size == 32_245) {
+                    assertEquals(Frames.TYPE_MIDDLE, next.frameType)
+                    assertEquals(16_124, next.payload.size)
+                    val last = parser.next()!!
+                    assertEquals(Frames.TYPE_LAST, last.frameType)
+                    assertEquals(1, last.payload.size)
+                } else {
+                    assertEquals(Frames.TYPE_LAST, next.frameType)
+                    assertEquals(5, next.payload.size)
+                }
+            }
+            assertNull(parser.next())
+        }
+    }
+
+    @Test fun `channel control messages cannot be fragmented`() {
+        assertThrows(IllegalArgumentException::class.java) {
+            Frames.writeMessage(ByteArrayOutputStream(), 1, false, Frames.MESSAGE_CONTROL, ByteArray(16_125)) { it }
+        }
+    }
+
+    @Test fun `malformed and mismatched fragment runs are rejected`() {
+        val first = Frames.Frame(1, Frames.TYPE_FIRST, true, 0, byteArrayOf(), 4)
+        val last = Frames.Frame(1, Frames.TYPE_LAST, true, 0, byteArrayOf())
+        assertThrows(IOException::class.java) { Frames.Assembler().offer(last, byteArrayOf(1)) }
+        val assembler = Frames.Assembler()
+        assembler.offer(first, byteArrayOf(1, 2))
+        assertThrows(IOException::class.java) { assembler.offer(last, byteArrayOf(3)) }
+        assembler.offer(first, byteArrayOf(1, 2))
+        assertThrows(IOException::class.java) { assembler.offer(last, byteArrayOf(3, 4, 5)) }
+        assembler.offer(first, byteArrayOf(1, 2))
+        assertThrows(IOException::class.java) { assembler.offer(first, byteArrayOf(1, 2)) }
+    }
+
+    @Test fun `oversized declared message is rejected before allocation`() {
+        val parser = Frames.Parser()
+        val frame = byteArrayOf(1, 1, 0, 1, 0x7f, -1, -1, -1, 0)
+        parser.append(frame, frame.size)
+        assertThrows(IOException::class.java) { parser.next() }
+    }
+}

gearslip/src/test/java/app/seb3thehacker/gearslip/ProtobufTest.kt

@@ -0,0 +1,24 @@
+package app.seb3thehacker.gearslip
+
+import org.junit.Assert.*
+import org.junit.Test
+
+class ProtobufTest {
+    @Test fun `malformed suffix invalidates the whole message`() {
+        for (suffix in listOf(byteArrayOf(0), byteArrayOf(18, -1), byteArrayOf(13, 1), byteArrayOf(17, 1))) {
+            assertTrue(Wire.fields(byteArrayOf(8, 2) + suffix).isEmpty())
+            assertNull(Protobuf.readInt32Field(byteArrayOf(8, 2) + suffix, 1))
+        }
+    }
+
+    @Test fun `lengths cannot wrap when narrowed to int`() {
+        val huge = byteArrayOf(18) + Protobuf.varint(0x1_0000_0001) + byteArrayOf(42)
+        assertTrue(Wire.fields(huge).isEmpty())
+    }
+
+    @Test fun `last singular field wins and negative int32 keeps its sign`() {
+        assertEquals(2, Protobuf.readInt32Field(byteArrayOf(8, 1, 8, 2), 1))
+        assertEquals(-3, Protobuf.readInt32Field(Protobuf.varintField(1, -3), 1))
+        assertEquals(8_803_621_255L, Protobuf.readInt64Field(Protobuf.varintField(1, 8_803_621_255L), 1))
+    }
+}

gearslip/src/test/java/app/seb3thehacker/gearslip/ProtocolVersionTest.kt

@@ -0,0 +1,23 @@
+package app.seb3thehacker.gearslip
+
+import org.junit.Assert.*
+import org.junit.Test
+
+class ProtocolVersionTest {
+    @Test fun `advertises supported version to older and newer 1x peers`() {
+        assertArrayEquals(byteArrayOf(0, 1, 0, 7, 0, 0), ProtocolVersion.respond(1, 3).bytes)
+        assertArrayEquals(byteArrayOf(0, 1, 0, 7, 0, 0), ProtocolVersion.respond(1, 7).bytes)
+        assertArrayEquals(byteArrayOf(0, 1, 0, 7, 0, 0), ProtocolVersion.respond(1, 9).bytes)
+    }
+
+    @Test fun `newer head units get the 1x answer they accept`() {
+        assertArrayEquals(byteArrayOf(0, 1, 0, 7, 0, 0), ProtocolVersion.respond(4, 2).bytes)
+        assertArrayEquals(byteArrayOf(0, 1, 0, 7, 0, 0), ProtocolVersion.respond(6, 1).bytes)
+    }
+
+    @Test fun `major version 0 is refused`() {
+        val response = ProtocolVersion.respond(0, 9)
+        assertFalse(response.supported)
+        assertArrayEquals(byteArrayOf(0, 1, 0, 7, -1, -1), response.bytes)
+    }
+}

gearslip/src/test/java/app/seb3thehacker/gearslip/ServiceDiscoveryChannelTest.kt

@@ -0,0 +1,36 @@
+package app.seb3thehacker.gearslip
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class ServiceDiscoveryChannelTest {
+    private fun service(id: Long, field: Int, payload: ByteArray = byteArrayOf()) =
+        Protobuf.bytesField(1, Protobuf.varintField(1, id) + Protobuf.bytesField(field, payload))
+
+    @Test fun `invalid channel IDs cannot alias the control or another service channel`() {
+        val config = Protobuf.varintField(1, 16000) + Protobuf.varintField(2, 16) + Protobuf.varintField(3, 1)
+        val audio = Protobuf.bytesField(3, config)
+        val microphone = Protobuf.bytesField(2, config)
+        val sensor = Protobuf.bytesField(1, Protobuf.varintField(1, 1))
+        for (id in listOf(-1L, 0L, 256L, 0x1_0000_0001L)) {
+            assertNull(ServiceDiscovery.findMediaStatusChannel(service(id, 9)))
+            assertNull(ServiceDiscovery.findNavStatusService(service(id, 8, Protobuf.varintField(1, 1000))))
+            assertNull(ServiceDiscovery.findVideoService(service(id, 3, Protobuf.bytesField(4, byteArrayOf()))))
+            assertNull(ServiceDiscovery.findInputService(service(id, 4)))
+            assertNull(ServiceDiscovery.findMicService(service(id, 5, microphone)))
+            assertNull(ServiceDiscovery.findSensorService(service(id, 2, sensor)))
+            assertTrue(ServiceDiscovery.findAudioServices(service(id, 3, audio)).isEmpty())
+        }
+        assertEquals(255, ServiceDiscovery.findMediaStatusChannel(service(255, 9)))
+    }
+
+    @Test fun `navigation discovery preserves the requested update interval`() {
+        val navigation = requireNotNull(ServiceDiscovery.findNavStatusService(service(6, 8, Protobuf.varintField(1, 1500))))
+        assertEquals(6, navigation.serviceId)
+        assertEquals(1500, navigation.minimumIntervalMs)
+        assertNull(ServiceDiscovery.findNavStatusService(service(6, 8)))
+        assertNull(ServiceDiscovery.findNavStatusService(service(6, 8, Protobuf.varintField(1, -1))))
+    }
+}

gearslip/src/test/java/app/seb3thehacker/gearslip/car/ClusterNavTest.kt

@@ -0,0 +1,61 @@
+package app.seb3thehacker.gearslip.car
+
+import app.seb3thehacker.gearslip.Protobuf
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.atomic.AtomicInteger
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class ClusterNavTest {
+    @Test fun `head unit minimum interval limits repeated navigation updates`() {
+        val first = CountDownLatch(1)
+        val next = CountDownLatch(1)
+        val count = AtomicInteger()
+        val nav = ClusterNav(6, 1000) { _, _ ->
+            if (count.incrementAndGet() == 1) first.countDown() else next.countDown()
+        }
+        try {
+            nav.onMessage(8, Protobuf.varintField(1, 0))
+            assertTrue(first.await(2, TimeUnit.SECONDS))
+            nav.onMessage(32769, byteArrayOf())
+            assertFalse("the fixed 500ms timer must not override the head unit", next.await(700, TimeUnit.MILLISECONDS))
+            assertTrue(next.await(2, TimeUnit.SECONDS))
+        } finally {
+            nav.stop()
+        }
+    }
+
+    @Test fun `head unit stop pauses updates and start resends current status`() {
+        val messages = mutableListOf<Int>()
+        val nav = ClusterNav(6) { id, _ -> messages += id }
+        // Drive polling synchronously so the test does not depend on a background timer.
+        val running = ClusterNav::class.java.getDeclaredField("running").apply { isAccessible = true }
+        val tick = ClusterNav::class.java.getDeclaredMethod("tick").apply { isAccessible = true }
+        running.set(nav, true)
+        try {
+            tick.invoke(nav)
+            assertEquals(listOf(32771), messages)
+            nav.onMessage(32770, byteArrayOf())
+            tick.invoke(nav)
+            assertEquals(1, messages.size)
+            nav.onMessage(32769, byteArrayOf())
+            tick.invoke(nav)
+            assertEquals(listOf(32771, 32771), messages)
+            nav.stop()
+            tick.invoke(nav)
+            assertEquals(2, messages.size)
+        } finally {
+            nav.stop()
+        }
+    }
+
+    @Test fun `missing channel open status does not start publishing`() {
+        val nav = ClusterNav(6) { _, _ -> error("channel was not accepted") }
+        nav.onMessage(8, byteArrayOf())
+        val running = ClusterNav::class.java.getDeclaredField("running").apply { isAccessible = true }
+        assertFalse(running.getBoolean(nav))
+    }
+}

gearslip/src/test/java/app/seb3thehacker/gearslip/protocol/InputProtocolTest.kt

@@ -0,0 +1,52 @@
+package app.seb3thehacker.gearslip.protocol
+
+import app.seb3thehacker.gearslip.Protobuf
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Test
+
+class InputProtocolTest {
+    private fun pointer(id: Int) = Protobuf.bytesField(1,
+        Protobuf.varintField(1, 100) + Protobuf.varintField(2, 200) + Protobuf.varintField(3, id.toLong()))
+
+    @Test fun `multitouch preserves pointer IDs and action index`() {
+        val body = pointer(7) + pointer(3) + Protobuf.varintField(2, 1) + Protobuf.varintField(3, 5)
+        val touch = requireNotNull(InputProtocol.touch(body, 800 to 480))
+        assertEquals(5, touch.action)
+        assertEquals(1, touch.actionIndex)
+        assertEquals(listOf(7, 3), touch.points.map { it.id })
+        assertEquals(100f, touch.points[1].x)
+    }
+
+    @Test fun `invalid pointer index is rejected instead of targeting a different finger`() {
+        assertNull(InputProtocol.touch(pointer(0) + Protobuf.varintField(2, 1), null))
+        assertNull(InputProtocol.touch(pointer(0) + Protobuf.varintField(2, -1), null))
+    }
+
+    @Test fun `missing required pointer fields and duplicate IDs are rejected`() {
+        assertNull(InputProtocol.touch(Protobuf.bytesField(1, Protobuf.varintField(1, 20)), null))
+        assertNull(InputProtocol.touch(pointer(1) + pointer(1), null))
+    }
+
+    @Test fun `pointer IDs must fit the Android motion event range`() {
+        for (id in listOf(-1L, 32L, 0x1_0000_0000L)) {
+            val body = Protobuf.bytesField(1, Protobuf.varintField(1, 100) +
+                Protobuf.varintField(2, 200) + Protobuf.varintField(3, id))
+            assertNull(InputProtocol.touch(body, null))
+        }
+        assertEquals(31, requireNotNull(InputProtocol.touch(pointer(31), null)).points.single().id)
+    }
+
+    @Test fun `oversized pointer sets are rejected before constructing motion events`() {
+        val body = (0..32).fold(byteArrayOf()) { bytes, id -> bytes + pointer(id) }
+        assertNull(InputProtocol.touch(body, null))
+    }
+
+    @Test fun `optional touch fields use down and first pointer defaults`() {
+        val touch = requireNotNull(InputProtocol.touch(pointer(0), 50 to 60))
+        assertEquals(0, touch.action)
+        assertEquals(0, touch.actionIndex)
+        assertEquals(49f, touch.points.single().x)
+        assertEquals(59f, touch.points.single().y)
+    }
+}