Fix state flow of mute UI updates on Android

android/core/src/main/java/com/stadiamaps/ferrostar/core/NavigationViewModel.kt

@@ -8,8 +8,10 @@ import com.stadiamaps.ferrostar.core.extensions.deviation
 import com.stadiamaps.ferrostar.core.extensions.progress
 import com.stadiamaps.ferrostar.core.extensions.remainingSteps
 import com.stadiamaps.ferrostar.core.extensions.visualInstruction
+import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
 import uniffi.ferrostar.GeographicCoordinate
@@ -99,18 +101,20 @@ class DefaultNavigationViewModel(
 ) : ViewModel(), NavigationViewModel {
 
   private var userLocation: UserLocation? = locationProvider.lastLocation
+  private val muteState: StateFlow<Boolean?> =
+      spokenInstructionObserver?.muteState ?: MutableStateFlow(null)
 
   override val uiState =
-      ferrostarCore.state
-          .map { coreState ->
+      combine(ferrostarCore.state, muteState) { a, b -> a to b }
+          .map { (coreState, muteState) ->
             val location = locationProvider.lastLocation
             userLocation =
                 when (coreState.tripState) {
                   is TripState.Navigating -> coreState.tripState.snappedUserLocation
                   is TripState.Complete,
                   TripState.Idle -> locationProvider.lastLocation
                 }
-            uiState(coreState, spokenInstructionObserver?.isMuted, location, userLocation)
+            uiState(coreState, muteState, location, userLocation)
             // This awkward dance is required because Kotlin doesn't have a way to map over
             // StateFlows
             // without converting to a generic Flow in the process.
@@ -134,7 +138,7 @@ class DefaultNavigationViewModel(
       Log.d("NavigationViewModel", "Spoken instruction observer is null, mute operation ignored.")
       return
     }
-    spokenInstructionObserver.isMuted = !spokenInstructionObserver.isMuted
+    spokenInstructionObserver.setMuted(!spokenInstructionObserver.isMuted)
   }
 
   // TODO: We can add a hook here to override the current road name.

android/core/src/main/java/com/stadiamaps/ferrostar/core/Speech.kt

@@ -3,6 +3,10 @@ package com.stadiamaps.ferrostar.core
 import android.content.Context
 import android.speech.tts.TextToSpeech
 import android.speech.tts.TextToSpeech.OnInitListener
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.update
 import uniffi.ferrostar.SpokenInstruction
 
 interface SpokenInstructionObserver {
@@ -17,7 +21,12 @@ interface SpokenInstructionObserver {
   /** Stops speech and clears the queue of spoken utterances. */
   fun stopAndClearQueue()
 
-  var isMuted: Boolean
+  fun setMuted(isMuted: Boolean)
+
+  val muteState: StateFlow<Boolean>
+
+  val isMuted: Boolean
+    get() = muteState.value
 }
 
 /** Observes the status of an [AndroidTtsObserver]. */
@@ -62,14 +71,18 @@ class AndroidTtsObserver(
     private const val TAG = "AndroidTtsObserver"
   }
 
-  override var isMuted: Boolean = false
-    set(value) {
-      field = value
+  private var _muteState: MutableStateFlow<Boolean> = MutableStateFlow(false)
 
-      if (value && tts?.isSpeaking == true) {
+  override fun setMuted(isMuted: Boolean) {
+    _muteState.update { _ ->
+      if (isMuted && tts?.isSpeaking == true) {
         tts?.stop()
       }
+      isMuted
     }
+  }
+
+  override val muteState: StateFlow<Boolean> = _muteState.asStateFlow()
 
   var tts: TextToSpeech?
     private set