Merge #63: a display density setting for car apps

# Conflicts:
#	gearslip/src/main/java/app/seb3thehacker/gearslip/ui/CarPreviewScreen.kt

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

@@ -310,7 +310,8 @@ class GearslipActivity : ComponentActivity(), Projection {
         val target = surface ?: return
         if (screenProjector != null) return
         val projector = ScreenProjector(this).also { screenProjector = it }
-        projector.start(target, frameWidth, frameHeight, frameDensity) { CarUi() }
+        // The frame's density, not frameDensity: that stays the car's own, for the phone mirror.
+        projector.start(target, frameWidth, frameHeight, CarEnvironment.frame.value.densityDpi) { CarUi() }
     }
 
     /**

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

@@ -22,6 +22,7 @@ import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalDensity
@@ -113,7 +114,11 @@ private fun LauncherScreen(onOpenGearslip: () -> Unit) {
         val (width, height) = px
         if (width <= 0 || height <= 0) return@BoxWithConstraints
         // Car-like text and buttons: 160dpi for every 480 pixels of height, as the car preview uses.
-        val density = (160 * height / 480).coerceIn(120, 640)
+        // This screen stands in for the car's, so hosted apps size to it and the density setting applies.
+        val density = remember(width, height) {
+            CarEnvironment.setDisplay(width, height, (160 * height / 480).coerceIn(120, 640))
+            CarEnvironment.frame.value.densityDpi
+        }
         // Before the projector starts, so the car UI's first screen already knows what to hide.
         DisposableEffect(Unit) {
             LauncherMode.setActive(true)

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

@@ -37,6 +37,9 @@ object CarEnvironment {
     private val frameFlow = MutableStateFlow(Frame(800, 480, 160))
     val frame: StateFlow<Frame> = frameFlow
 
+    /** The density the car reported; [frame] carries the one the car UI and its apps draw at. */
+    private var carDensityDpi = 160
+
     val phoneDark: StateFlow<Boolean> = phoneDarkFlow
     val darkOutside: StateFlow<Boolean> = darkOutsideFlow
     val battery: StateFlow<Battery> = batteryFlow
@@ -95,8 +98,18 @@ object CarEnvironment {
     }
 
     fun setDisplay(width: Int, height: Int, densityDpi: Int) {
-        displayFlow.value = "${width}x$height @ ${densityDpi}dpi"
+        carDensityDpi = densityDpi
-        frameFlow.value = Frame(width, height, densityDpi)
+        val dpi = CarSettings.effectiveDensity(densityDpi)
+        displayFlow.value = "${width}x$height @ ${dpi}dpi"
+        frameFlow.value = Frame(width, height, dpi)
+    }
+
+    /**
+     * Takes up the density setting. It's read only as a session starts, so the display and the
+     * apps on it can't disagree mid-drive; a session with no car behind it, the preview, asks here.
+     */
+    fun applyDensity() {
+        frameFlow.value = frameFlow.value.copy(densityDpi = CarSettings.effectiveDensity(carDensityDpi))
     }
 
     fun start(context: Context) {

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

@@ -53,6 +53,7 @@ enum class NavBarMode { SHOW, HIDE_NAVIGATING, HIDE }
 object CarSettings {
 
     private const val KEY_SCALE = "car_scale"
+    private const val KEY_DENSITY = "car_density"
     private const val KEY_OPEN = "car_open_on_connect"
     private const val KEY_NIGHT = "car_night_mode"
     private const val KEY_PIPE_AUDIO = "car_pipe_audio"
@@ -99,6 +100,7 @@ private const val KEY_CLUSTER_VIDEO = "cluster_video_enabled"
     private lateinit var app: Context
 
     private val scaleFlow = MutableStateFlow(1f)
+    private val carDensityFlow = MutableStateFlow(DENSITY_FROM_CAR)
     private val openFlow = MutableStateFlow(HOME)
     private val nightFlow = MutableStateFlow(NightMode.AUTO)
     private val pipeAudioFlow = MutableStateFlow(true)
@@ -245,6 +247,16 @@ private const val KEY_CLUSTER_VIDEO = "cluster_video_enabled"
     val moreLyrics: StateFlow<Boolean> = moreLyricsFlow
 
     val scale: StateFlow<Float> = scaleFlow
+
+    /** [carDensity] when it leaves the choice to the car. */
+    const val DENSITY_FROM_CAR = 0
+    val DENSITIES = listOf(160, 180, 200, 220, 240)
+
+    /** An absolute DPI for the car UI and its apps; the video's resolution doesn't change with it. */
+    val carDensity: StateFlow<Int> = carDensityFlow
+
+    /** The density to draw at, for a car or preview that would otherwise use [carDpi]. */
+    fun effectiveDensity(carDpi: Int) = carDensityFlow.value.takeIf { it != DENSITY_FROM_CAR } ?: carDpi
     val openOnConnect: StateFlow<String> = openFlow
     val nightMode: StateFlow<NightMode> = nightFlow
 
@@ -336,6 +348,7 @@ private const val KEY_CLUSTER_VIDEO = "cluster_video_enabled"
     fun init(context: Context) {
         app = context.applicationContext
         scaleFlow.value = AppSettings.getString(app, KEY_SCALE, "1.0").toFloatOrNull() ?: 1f
+        carDensityFlow.value = AppSettings.getString(app, KEY_DENSITY, "").toIntOrNull()?.takeIf { it in DENSITIES } ?: DENSITY_FROM_CAR
         openFlow.value = AppSettings.getString(app, KEY_OPEN, HOME)
         lastNavFlow.value = AppSettings.getString(app, KEY_LAST_NAV, "").ifEmpty { null }
         lastMediaFlow.value = AppSettings.getString(app, KEY_LAST_MEDIA, "").ifEmpty { null }
@@ -396,6 +409,11 @@ private const val KEY_CLUSTER_VIDEO = "cluster_video_enabled"
         AppSettings.putString(app, KEY_SCALE, value.toString())
     }
 
+    fun setCarDensity(dpi: Int) {
+        carDensityFlow.value = dpi
+        AppSettings.putString(app, KEY_DENSITY, dpi.toString())
+    }
+
     fun setOpenOnConnect(id: String) {
         openFlow.value = id
         AppSettings.putString(app, KEY_OPEN, id)

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

@@ -60,7 +60,7 @@ import app.seb3thehacker.gearslip.car.CarUi
 @Composable
 fun CarPreviewScreen(onBack: () -> Unit) {
     val context = LocalContext.current
-    val frame by CarEnvironment.frame.collectAsStateWithLifecycle()
+    val frame by remember { CarEnvironment.frame.also { CarEnvironment.applyDensity() } }.collectAsStateWithLifecycle()
     // 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
@@ -291,7 +291,7 @@ private fun previewFrame(
     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))
+    fun carLike(w: Int, h: Int) = Triple(w, h, app.seb3thehacker.gearslip.car.CarSettings.effectiveDensity((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 ->

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

@@ -66,6 +66,8 @@ enum class CarGroup(@param:StringRes val title: Int) {
 @Composable
 private fun sizeChoices() = listOf(1f to stringResource(R.string.choice_size_normal), 1.25f to stringResource(R.string.choice_size_large), 1.5f to stringResource(R.string.choice_size_xlarge))
 @Composable
+private fun densityChoices() = listOf(CarSettings.DENSITY_FROM_CAR to stringResource(R.string.choice_density_car)) + CarSettings.DENSITIES.map { it to stringResource(R.string.choice_density_dpi, it) }
+@Composable
 private fun themeChoices() = listOf(AppTheme.PHONE to stringResource(R.string.choice_theme_phone), AppTheme.LIGHT to stringResource(R.string.choice_theme_light), AppTheme.DARK to stringResource(R.string.choice_theme_dark))
 @Composable
 private fun darkChoices() = listOf(
@@ -212,6 +214,7 @@ internal fun CarGroupScreen(group: CarGroup, onBack: () -> Unit) {
 @Composable
 private fun GroupRows(group: CarGroup) {
     val scale by CarSettings.scale.collectAsState()
+    val density by CarSettings.carDensity.collectAsState()
     val open by CarSettings.openOnConnect.collectAsState()
     val night by CarSettings.nightMode.collectAsState()
     val units by CarSettings.units.collectAsState()
@@ -241,6 +244,8 @@ private fun GroupRows(group: CarGroup) {
             SettingsDivider()
             Choice(stringResource(R.string.car_size), sizeChoices(), scale, CarSettings::setScale)
             SettingsDivider()
+            Choice(stringResource(R.string.car_density), densityChoices(), density, CarSettings::setCarDensity, note = stringResource(R.string.car_density_note))
+            SettingsDivider()
             Choice(stringResource(R.string.car_app_theme), themeChoices(), theme, CarSettings::setAppTheme)
             SettingsDivider()
             if (theme != AppTheme.LIGHT) {
@@ -358,11 +363,12 @@ private fun <T> List<Pair<T, String>>.label(value: T): String = firstOrNull { it
 
 /** A setting with a few named choices: its current one shown, the rest a tap away. */
 @Composable
-private fun <T> Choice(title: String, choices: List<Pair<T, String>>, selected: T, onSelect: (T) -> Unit) {
+private fun <T> Choice(title: String, choices: List<Pair<T, String>>, selected: T, onSelect: (T) -> Unit, note: String? = null) {
     var menu by remember { mutableStateOf(false) }
     SettingsRow(
         title,
         Modifier.clickable { menu = true },
+        subtitle = note,
         trailing = {
             // The menu hangs from the value it changes, at the row's end.
             Box {

gearslip/src/main/res/values/strings.xml

@@ -192,6 +192,10 @@
     <string name="car_group_same">These are the same settings as Settings in the car. A change here shows there too.</string>
     <string name="car_open_on_connect">Open on connect</string>
     <string name="car_size">Size</string>
+    <string name="car_density">Car display density</string>
+    <string name="car_density_note">Larger text and controls, including in apps. Try 200 DPI with Size on Normal. Reconnect the car or reopen the preview to apply it. If controls clip, choose a lower DPI or From car.</string>
+    <string name="choice_density_car">From car</string>
+    <string name="choice_density_dpi">%1$d DPI</string>
     <string name="car_app_theme">App theme</string>
     <string name="car_dark_mode">Dark mode</string>
     <string name="car_buttons">Buttons</string>

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

@@ -0,0 +1,91 @@
+package app.seb3thehacker.gearslip.car
+
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+
+class CarDensityTest {
+    private val context = InMemoryContext()
+
+    private fun density() = CarEnvironment.frame.value.densityDpi
+
+    @Before
+    fun startFromTheCar() {
+        CarSettings.init(context)
+        CarEnvironment.setDisplay(800, 480, 160)
+    }
+
+    @Test
+    fun fromCarKeepsEachCarsOwnDensity() {
+        assertEquals(CarSettings.DENSITY_FROM_CAR, CarSettings.carDensity.value)
+        for (dpi in listOf(120, 180, 213)) {
+            CarEnvironment.setDisplay(800, 480, dpi)
+            assertEquals(dpi, density())
+        }
+    }
+
+    @Test
+    fun aChosenDensityReachesEverythingThatReadsTheFrame() {
+        for (dpi in CarSettings.DENSITIES) {
+            CarSettings.setCarDensity(dpi)
+            CarEnvironment.setDisplay(800, 480, 160)
+            assertEquals(dpi, density())
+        }
+    }
+
+    @Test
+    fun aChosenDensityLeavesTheResolutionAlone() {
+        CarSettings.setCarDensity(240)
+        CarEnvironment.setDisplay(1280, 720, 160)
+        assertEquals(CarEnvironment.Frame(1280, 720, 240), CarEnvironment.frame.value)
+    }
+
+    @Test
+    fun aNewChoiceWaitsForTheNextSession() {
+        CarSettings.setCarDensity(200)
+        CarEnvironment.setDisplay(800, 480, 160)
+        CarSettings.setCarDensity(240)
+        assertEquals(200, density())
+        CarEnvironment.setDisplay(800, 480, 160)
+        assertEquals(240, density())
+    }
+
+    @Test
+    fun thePreviewTakesUpANewChoiceWhenItOpens() {
+        CarSettings.setCarDensity(200)
+        CarEnvironment.applyDensity()
+        assertEquals(200, density())
+    }
+
+    @Test
+    fun goingBackToFromCarRestoresTheCarsOwnDensity() {
+        CarSettings.setCarDensity(240)
+        CarEnvironment.setDisplay(800, 480, 180)
+        CarSettings.setCarDensity(CarSettings.DENSITY_FROM_CAR)
+        CarEnvironment.applyDensity()
+        assertEquals(180, density())
+    }
+
+    @Test
+    fun aPreviewSizedForThePhoneFollowsTheChoiceToo() {
+        assertEquals(213, CarSettings.effectiveDensity(213))
+        CarSettings.setCarDensity(200)
+        assertEquals(200, CarSettings.effectiveDensity(213))
+    }
+
+    @Test
+    fun theChoiceSurvivesARestart() {
+        CarSettings.setCarDensity(220)
+        CarSettings.init(context)
+        assertEquals(220, CarSettings.carDensity.value)
+    }
+
+    @Test
+    fun aSavedDensityGearslipDoesNotOfferFallsBackToTheCar() {
+        for (saved in listOf("201", "-1", "broken", "")) {
+            context.stored["car_density"] = saved
+            CarSettings.init(context)
+            assertEquals(CarSettings.DENSITY_FROM_CAR, CarSettings.carDensity.value)
+        }
+    }
+}