protocol: service discovery sends Gearslip's icon at three sizes and a session ID, like a real phone

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

@@ -401,6 +401,7 @@ class GearslipActivity : ComponentActivity(), Projection {
             identityProvider = { CertProvider.load(this) },
             projection = this,
             vehicleProfileFor = { info -> VehicleProfiles.find(VehicleProfiles.load(this), info) },
+            phoneIcons = { PhoneIcons.pngs(this) },
         )
         this.runner = runner
         worker = Thread { runner.run() }.apply { name = "gearslip"; start() }
@@ -423,6 +424,7 @@ class GearslipActivity : ComponentActivity(), Projection {
             projection = this,
             vehicleProfileFor = { info -> VehicleProfiles.find(VehicleProfiles.load(this), info) },
             wireless = true,
+            phoneIcons = { PhoneIcons.pngs(this) },
         )
         this.runner = runner
         worker = Thread { runner.run() }.apply { name = "gearslip"; start() }

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

@@ -48,6 +48,8 @@ class GearslipRunner(
     private val vehicleProfileFor: (ServiceDiscovery.HeadUnitInfo) -> VehicleProfile? = { null },
     /** Over Wi-Fi rather than USB: the video is sent smaller so the link keeps up. */
     private val wireless: Boolean = false,
+    /** Gearslip's icon as 32, 64 and 128 px PNGs, for the car's phone tile. See [PhoneIcons]. */
+    private val phoneIcons: () -> List<ByteArray> = { emptyList() },
 ) {
     private val log = GearslipLog.tagged("PROTO")
 
@@ -446,11 +448,20 @@ class GearslipRunner(
         if (authenticationFailed) running = false
     }
 
+    /**
+     * What a real phone sends here: its icon at three sizes (fields 1 to 3), a label, its model,
+     * and a session ID that's new each connection (field 6). A 2017 Hyundai on protocol 1.0
+     * never answered the request when it had only the label and model (issue #47).
+     */
     private fun sendServiceDiscoveryRequest() {
-        val body = Protobuf.stringField(4, "Gearslip") + // label_text
+        val icons = runCatching(phoneIcons).getOrDefault(emptyList())
-            Protobuf.stringField(5, Build.MODEL)        // device_name
+        var body = ByteArray(0)
+        icons.take(3).forEachIndexed { i, png -> body += Protobuf.bytesField(i + 1, png) } // small, medium, large icon
+        body += Protobuf.stringField(4, "Gearslip") + // label_text
+            Protobuf.stringField(5, Build.MODEL) + // device_name
+            Protobuf.bytesField(6, Protobuf.stringField(1, java.util.UUID.randomUUID().toString())) // session ID
         send(MSG_SERVICE_DISCOVERY_REQUEST, body, encrypted = true)
-        log.i("-> ServiceDiscoveryRequest (encrypted)")
+        log.i("-> ServiceDiscoveryRequest (encrypted, ${icons.size} icons, ${body.size} bytes)")
     }
 
     private fun onServiceDiscoveryResponse(body: ByteArray) {

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

@@ -0,0 +1,34 @@
+package app.seb3thehacker.gearslip
+
+import android.content.Context
+import android.graphics.Bitmap
+import android.graphics.Canvas
+import java.io.ByteArrayOutputStream
+
+/**
+ * Gearslip's own icon as the PNGs a phone hands the car in its ServiceDiscoveryRequest, at the
+ * 32, 64 and 128 px a real phone sends. Cars draw the phone's tile on their home screen from
+ * them, and older head units may wait for them before answering at all.
+ */
+object PhoneIcons {
+
+    private val SIZES = intArrayOf(32, 64, 128)
+
+    @Volatile private var cached: List<ByteArray>? = null
+
+    /** The three PNGs, smallest first; empty if the icon can't be drawn. */
+    fun pngs(context: Context): List<ByteArray> = cached ?: runCatching {
+        val icon = context.packageManager.getApplicationIcon(context.applicationInfo).mutate()
+        SIZES.map { size ->
+            val bitmap = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888)
+            icon.setBounds(0, 0, size, size)
+            icon.draw(Canvas(bitmap))
+            val png = ByteArrayOutputStream()
+            bitmap.compress(Bitmap.CompressFormat.PNG, 100, png)
+            bitmap.recycle()
+            png.toByteArray()
+        }
+    }.onFailure { GearslipLog.w("phone icons: couldn't draw them (${it.message})") }
+        .getOrDefault(emptyList())
+        .also { if (it.isNotEmpty()) cached = it }
+}