ui(android): drop snackbar + hardware volume keys when UPnP route active

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/player/PlayerController.kt

@@ -20,6 +20,7 @@ import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.receiveAsFlow
@@ -59,7 +60,15 @@ class PlayerController @Inject constructor(
     @ApplicationContext private val context: Context,
     @ApplicationScope private val scope: CoroutineScope,
     private val radio: RadioController,
+    private val playerFactory: PlayerFactory,
 ) {
+
+    /**
+     * UPnP drop events surfaced from [PlayerFactory.dropEvents]. NowPlaying
+     * collects this into its snackbar host so a transport / poll failure
+     * during UPnP playback shows "Disconnected from <name>" to the user.
+     */
+    val dropEvents: SharedFlow<String> = playerFactory.dropEvents
     private val sessionToken =
         SessionToken(context, ComponentName(context, MinstrelPlayerService::class.java))
 

android/app/src/main/java/com/fabledsword/minstrel/player/output/OutputPickerViewModel.kt

@@ -24,6 +24,7 @@ import javax.inject.Inject
 @HiltViewModel
 class OutputPickerViewModel @Inject constructor(
     private val controller: OutputPickerController,
+    private val activeUpnpHolder: ActiveUpnpHolder,
 ) : ViewModel() {
 
     val routes: StateFlow<RouteSnapshot> = controller.routesState
@@ -33,6 +34,9 @@ class OutputPickerViewModel @Inject constructor(
             initialValue = controller.routesState.value,
         )
 
+    val activeUpnp: StateFlow<ActiveUpnp?> = activeUpnpHolder.active
+        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(STOP_TIMEOUT_MS), null)
+
     private val sheetVisibleInternal = MutableStateFlow(false)
     val sheetVisible: StateFlow<Boolean> = sheetVisibleInternal.asStateFlow()
 

android/app/src/main/java/com/fabledsword/minstrel/player/ui/NowPlayingScreen.kt

@@ -8,6 +8,7 @@ import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.animation.ExperimentalSharedTransitionApi
 import androidx.compose.foundation.background
+import androidx.compose.foundation.focusable
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.foundation.layout.Arrangement
@@ -50,10 +51,19 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
+import androidx.compose.ui.focus.FocusRequester
+import androidx.compose.ui.focus.focusRequester
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
+import androidx.compose.ui.input.key.Key
+import androidx.compose.ui.input.key.KeyEvent
+import androidx.compose.ui.input.key.KeyEventType
+import androidx.compose.ui.input.key.key
+import androidx.compose.ui.input.key.onKeyEvent
+import androidx.compose.ui.input.key.type
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextOverflow
@@ -74,11 +84,13 @@ import com.composables.icons.lucide.Shuffle
 import com.composables.icons.lucide.SkipBack
 import com.composables.icons.lucide.SkipForward
 import com.fabledsword.minstrel.player.RepeatMode
+import com.fabledsword.minstrel.player.output.ActiveUpnp
 import com.fabledsword.minstrel.player.output.DeviceChip
 import com.fabledsword.minstrel.player.output.OutputPickerSheet
 import com.fabledsword.minstrel.player.output.OutputPickerViewModel
 import com.fabledsword.minstrel.player.output.OutputRoute
 import com.fabledsword.minstrel.player.output.RouteSnapshot
+import kotlinx.coroutines.launch
 import com.fabledsword.minstrel.nav.AlbumDetail
 import com.fabledsword.minstrel.nav.ArtistDetail
 import com.fabledsword.minstrel.nav.HERO_KEY_NOW_PLAYING_COVER
@@ -129,27 +141,30 @@ fun NowPlayingScreen(
             snackbarHostState.showSnackbar(msg)
         }
     }
+    LaunchedEffect(Unit) {
+        viewModel.dropEvents.collect { snackbarHostState.showSnackbar("Disconnected from $it") }
+    }
     val track = state.currentTrack
     if (track == null) {
-        // Session torn down (queue finished + auto-stop, or user cleared
+        NowPlayingNullTrackGuard(navController, viewModel)
-        // the queue from elsewhere). Pop back to whichever shell screen
-        // launched NowPlaying rather than stranding the user on an
-        // EmptyState with no escape. A short delay swallows the
-        // momentary null during MediaController IPC bind on cold-mount.
-        LaunchedEffect(Unit) {
-            kotlinx.coroutines.delay(POP_GRACE_MS)
-            if (viewModel.uiState.value.currentTrack == null) {
-                navController.popBackStack()
-            }
-        }
         return
     }
+    val outputViewModel: OutputPickerViewModel = hiltViewModel()
+    val activeUpnp by outputViewModel.activeUpnp.collectAsStateWithLifecycle()
+    val onKeyEvent = rememberUpnpVolumeKeyHandler(activeUpnp)
+    val focusRequester = remember { FocusRequester() }
+    LaunchedEffect(activeUpnp) { if (activeUpnp != null) focusRequester.requestFocus() }
     val dominant = rememberDominantColor(track.coverUrl)
     val dismissConnection = rememberDragDismissConnection(
         onDismiss = { navController.popBackStack() },
     )
     Scaffold(
-        modifier = Modifier.fillMaxSize().nestedScroll(dismissConnection),
+        modifier = Modifier
+            .fillMaxSize()
+            .nestedScroll(dismissConnection)
+            .focusRequester(focusRequester)
+            .focusable()
+            .onKeyEvent(onKeyEvent),
         topBar = { NowPlayingTopBar(onClose = { navController.popBackStack() }) },
         snackbarHost = { SnackbarHost(snackbarHostState) },
         containerColor = Color.Transparent,
@@ -166,11 +181,32 @@ fun NowPlayingScreen(
                 navController = navController,
                 viewModel = viewModel,
                 trackActionsViewModel = trackActionsViewModel,
+                outputViewModel = outputViewModel,
             )
         }
     }
 }
 
+/**
+ * Null-track guard extracted from [NowPlayingScreen] to keep that
+ * function under detekt's LongMethod ceiling. Session torn down
+ * (queue finished + auto-stop, or user cleared the queue from
+ * elsewhere). Pops back after a short grace delay so a momentary
+ * null during MediaController IPC bind on cold-mount doesn't flash.
+ */
+@Composable
+private fun NowPlayingNullTrackGuard(
+    navController: NavHostController,
+    viewModel: PlayerViewModel,
+) {
+    LaunchedEffect(Unit) {
+        kotlinx.coroutines.delay(POP_GRACE_MS)
+        if (viewModel.uiState.value.currentTrack == null) {
+            navController.popBackStack()
+        }
+    }
+}
+
 @Composable
 private fun dominantGradient(top: Color): Brush {
     val base = MaterialTheme.colorScheme.background
@@ -270,6 +306,7 @@ private fun NowPlayingTopBar(onClose: () -> Unit) {
     )
 }
 
+@Suppress("LongParameterList") // Compose screen wiring — layout args, not logic
 @Composable
 private fun NowPlayingBody(
     inner: androidx.compose.foundation.layout.PaddingValues,
@@ -278,10 +315,10 @@ private fun NowPlayingBody(
     navController: NavHostController,
     viewModel: PlayerViewModel,
     trackActionsViewModel: TrackActionsViewModel,
+    outputViewModel: OutputPickerViewModel,
 ) {
     val isLiked by trackActionsViewModel.isLikedFlow(track.id)
         .collectAsStateWithLifecycle(initialValue = false)
-    val outputViewModel: OutputPickerViewModel = hiltViewModel()
     val routes by outputViewModel.routes.collectAsStateWithLifecycle()
     val sheetVisible by outputViewModel.sheetVisible.collectAsStateWithLifecycle()
     val permissionDenied = rememberBluetoothPermissionState(sheetVisible)
@@ -703,3 +740,40 @@ private fun TransportRow(
         }
     }
 }
+
+/**
+ * Returns a key-event handler that intercepts volume-up/down when a UPnP
+ * route is active and routes the step through [ActiveUpnp.rendering].
+ * Volume is cached locally so rapid key presses don't each wait on a
+ * getVolume() round-trip. Returns false (not consumed) for every event
+ * when no UPnP route is active so the system handles volume normally.
+ */
+@Composable
+private fun rememberUpnpVolumeKeyHandler(activeUpnp: ActiveUpnp?): (KeyEvent) -> Boolean {
+    val scope = rememberCoroutineScope()
+    val cache = remember { VolumeCache() }
+    return remember(activeUpnp) {
+        handler@{ event: KeyEvent ->
+            val rc = activeUpnp?.rendering ?: return@handler false
+            if (event.type != KeyEventType.KeyDown) return@handler false
+            val delta = when (event.key) {
+                Key.VolumeUp -> VOLUME_KEY_STEP
+                Key.VolumeDown -> -VOLUME_KEY_STEP
+                else -> return@handler false
+            }
+            scope.launch {
+                val current = cache.value ?: runCatching { rc.getVolume() }.getOrNull() ?: 0
+                val next = (current + delta).coerceIn(VOLUME_MIN_PERCENT, VOLUME_MAX_PERCENT)
+                cache.value = next
+                runCatching { rc.setVolume(next) }
+            }
+            true
+        }
+    }
+}
+
+private class VolumeCache(var value: Int? = null)
+
+private const val VOLUME_KEY_STEP = 5
+private const val VOLUME_MIN_PERCENT = 0
+private const val VOLUME_MAX_PERCENT = 100

android/app/src/main/java/com/fabledsword/minstrel/player/ui/PlayerViewModel.kt

@@ -4,6 +4,7 @@ import androidx.lifecycle.ViewModel
 import com.fabledsword.minstrel.player.PlayerController
 import com.fabledsword.minstrel.player.PlayerUiState
 import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.StateFlow
 import javax.inject.Inject
 
@@ -24,6 +25,7 @@ class PlayerViewModel @Inject constructor(
 ) : ViewModel() {
 
     val uiState: StateFlow<PlayerUiState> = controller.uiState
+    val dropEvents: SharedFlow<String> = controller.dropEvents
 
     fun play() = controller.play()
     fun pause() = controller.pause()