feat: add a keep-screen-on toggle for now playing

A screen timeout mid-album is a common complaint for a music player: the
phone lies on a table while art or lyrics are on screen and the display
sleeps. Add a Settings toggle under Playback, off by default, that holds
the screen awake while now playing is open. The flag rides on the now
playing overlay through Compose's keepScreenOn modifier, and since the
overlay is only composed while expanded, collapsing it releases the flag
without any window-flag lifecycle handling.

Closes austinried/subtracks#201

app/src/main/kotlin/com/subtracks/data/prefs/UserPreferences.kt

@@ -174,6 +174,14 @@ class UserPreferences(
 
     private val replayGainPreampKey = floatPreferencesKey("replay_gain_preamp_db")
 
+    fun keepScreenOn(): Flow<Boolean> = store.data.map { prefs -> prefs[keepScreenOnKey] ?: false }
+
+    suspend fun setKeepScreenOn(enabled: Boolean) {
+        store.edit { prefs -> prefs[keepScreenOnKey] = enabled }
+    }
+
+    private val keepScreenOnKey = booleanPreferencesKey("keep_screen_on")
+
     fun offlineMode(): Flow<Boolean> = store.data.map { prefs -> prefs[offlineModeKey] ?: false }
 
     suspend fun setOfflineMode(enabled: Boolean) {

app/src/main/kotlin/com/subtracks/ui/playback/NowPlayingScreen.kt

@@ -60,6 +60,7 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.keepScreenOn
 import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.platform.testTag
@@ -76,6 +77,7 @@ import com.subtracks.R
 import com.subtracks.data.model.CoverArtRef
 import com.subtracks.data.model.QueueKind
 import com.subtracks.data.model.Song
+import com.subtracks.data.prefs.UserPreferences
 import com.subtracks.data.repo.DownloadRepository
 import com.subtracks.data.repo.LibraryRepository
 import com.subtracks.data.source.StarType
@@ -191,8 +193,10 @@ fun NowPlayingRoute(
     controller: PlaybackController = koinInject(),
     libraryRepository: LibraryRepository = koinInject(),
     downloadRepository: DownloadRepository = koinInject(),
+    userPreferences: UserPreferences = koinInject(),
 ) {
     val state by controller.state.collectAsStateWithLifecycle()
+    val keepScreenOn by userPreferences.keepScreenOn().collectAsStateWithLifecycle(initialValue = false)
     val positionMs by controller.positionMs.collectAsStateWithLifecycle()
     val sourceId = state.context?.sourceId
     val songId = state.item?.id
@@ -272,6 +276,7 @@ fun NowPlayingRoute(
         starred = song?.starred != null,
         onToggleStar = song?.let { s -> { setStar(StarType.Song, s.id, s.starred == null) } },
         onSeek = controller::seekTo,
+        keepScreenOn = keepScreenOn,
         modifier = modifier,
     )
 }
@@ -290,6 +295,7 @@ fun NowPlayingScreen(
     onNext: () -> Unit,
     onPrevious: () -> Unit,
     modifier: Modifier = Modifier,
+    keepScreenOn: Boolean = false,
     onSkipPrevious: () -> Unit = onPrevious,
     onShuffle: () -> Unit = {},
     onRepeat: () -> Unit = {},
@@ -366,7 +372,12 @@ fun NowPlayingScreen(
 
     CompositionLocalProvider(LocalContentColor provides MaterialTheme.colorScheme.onBackground) {
         ArtworkTheme(artwork) {
-            Box(modifier.fillMaxSize().background(MaterialTheme.colorScheme.background)) {
+            Box(
+                modifier
+                    .fillMaxSize()
+                    .background(MaterialTheme.colorScheme.background)
+                    .then(if (keepScreenOn) Modifier.keepScreenOn() else Modifier),
+            ) {
                 HeroGradient(
                     colors = artwork,
                     scrollPx = { 0f },

app/src/main/kotlin/com/subtracks/ui/settings/SettingsScreen.kt

@@ -123,6 +123,7 @@ fun SettingsRoute(
     val downloadQuality by viewModel.downloadQuality.collectAsStateWithLifecycle()
     val downloadOverMetered by viewModel.downloadOverMetered.collectAsStateWithLifecycle()
     val scrobbling by viewModel.scrobbling.collectAsStateWithLifecycle()
+    val keepScreenOn by viewModel.keepScreenOn.collectAsStateWithLifecycle()
     val offline by viewModel.offline.collectAsStateWithLifecycle()
     val verboseLogging by viewModel.verboseLogging.collectAsStateWithLifecycle()
     val replayGainMode by viewModel.replayGainMode.collectAsStateWithLifecycle()
@@ -142,6 +143,7 @@ fun SettingsRoute(
         scrobbling = scrobbling,
         replayGainMode = replayGainMode,
         replayGainPreamp = replayGainPreamp,
+        keepScreenOn = keepScreenOn,
         offline = offline,
         verboseLogging = verboseLogging,
         onSelectSource = viewModel::selectSource,
@@ -156,6 +158,7 @@ fun SettingsRoute(
         onScrobblingChange = viewModel::setScrobbling,
         onReplayGainModeChange = viewModel::setReplayGainMode,
         onReplayGainPreampChange = viewModel::setReplayGainPreamp,
+        onKeepScreenOnChange = viewModel::setKeepScreenOn,
         onOfflineChange = viewModel::setOfflineMode,
         onVerboseLoggingChange = viewModel::setVerboseLogging,
         onAddServer = onAddServer,
@@ -195,6 +198,7 @@ fun SettingsScreen(
     downloadOverMetered: Boolean,
     scrobbling: Boolean,
     modifier: Modifier = Modifier,
+    keepScreenOn: Boolean = false,
     offline: Boolean = false,
     verboseLogging: Boolean = false,
     syncMode: SyncMode = SyncMode.WifiOnly,
@@ -213,6 +217,7 @@ fun SettingsScreen(
     onScrobblingChange: (Boolean) -> Unit,
     onReplayGainModeChange: (ReplayGainMode) -> Unit = {},
     onReplayGainPreampChange: (Float) -> Unit = {},
+    onKeepScreenOnChange: (Boolean) -> Unit = {},
     onOfflineChange: (Boolean) -> Unit = {},
     onVerboseLoggingChange: (Boolean) -> Unit = {},
     onAddServer: () -> Unit,
@@ -380,6 +385,26 @@ fun SettingsScreen(
                     colors = ListItemDefaults.colors(containerColor = Color.Transparent),
                 )
             }
+            item {
+                ListItem(
+                    headlineContent = { Text(stringResource(R.string.settings_music_options_keep_screen_on_title)) },
+                    supportingContent = { Text(stringResource(R.string.settings_music_options_keep_screen_on_description)) },
+                    trailingContent = {
+                        Switch(
+                            checked = keepScreenOn,
+                            onCheckedChange = onKeepScreenOnChange,
+                            colors =
+                                SwitchDefaults.colors(
+                                    uncheckedThumbColor = MaterialTheme.colorScheme.onSurfaceVariant,
+                                    uncheckedTrackColor = MaterialTheme.colorScheme.surfaceVariant,
+                                    uncheckedBorderColor = MaterialTheme.colorScheme.outline,
+                                ),
+                        )
+                    },
+                    modifier = Modifier.clickable { onKeepScreenOnChange(!keepScreenOn) },
+                    colors = ListItemDefaults.colors(containerColor = Color.Transparent),
+                )
+            }
             item { SectionHeader(stringResource(R.string.downloads_title)) }
             item {
                 ListItem(

app/src/main/kotlin/com/subtracks/ui/settings/SettingsViewModel.kt

@@ -76,6 +76,11 @@ class SettingsViewModel(
             .replayGainPreampDb()
             .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), 0f)
 
+    val keepScreenOn: StateFlow<Boolean> =
+        userPreferences
+            .keepScreenOn()
+            .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), false)
+
     val offline: StateFlow<Boolean> = sourceRepository.offline
 
     val verboseLogging: StateFlow<Boolean> =
@@ -134,4 +139,8 @@ class SettingsViewModel(
     fun setReplayGainPreamp(value: Float) {
         viewModelScope.launch { userPreferences.setReplayGainPreampDb(value) }
     }
+
+    fun setKeepScreenOn(enabled: Boolean) {
+        viewModelScope.launch { userPreferences.setKeepScreenOn(enabled) }
+    }
 }