make onBackPress action adhere to the ui flow

new-player/src/main/java/net/newpipe/newplayer/model/UIModeState.kt

@@ -153,6 +153,16 @@ enum class UIModeState {
         FULLSCREEN_VIDEO_STREAM_SELECT -> PlayMode.FULLSCREEN_VIDEO
     }
 
+    fun getNextModeWhenBackPressed() = when(this) {
+        EMBEDDED_VIDEO_CHAPTER_SELECT -> EMBEDDED_VIDEO
+        EMBEDDED_VIDEO_STREAM_SELECT -> EMBEDDED_VIDEO
+        FULLSCREEN_VIDEO -> EMBEDDED_VIDEO
+        FULLSCREEN_VIDEO_STREAM_SELECT -> FULLSCREEN_VIDEO
+        FULLSCREEN_VIDEO_CHAPTER_SELECT -> FULLSCREEN_VIDEO
+        FULLSCREEN_VIDEO_CONTROLLER_UI -> EMBEDDED_VIDEO
+        else -> null
+    }
+
     companion object {
         fun fromPlayMode(playMode: PlayMode?) =
             if (playMode != null)

new-player/src/main/java/net/newpipe/newplayer/model/VideoPlayerViewModel.kt

@@ -37,6 +37,7 @@ interface VideoPlayerViewModel {
     var maxContentRatio: Float
     var contentFitMode: ContentScale
     val embeddedPlayerDraggedDownBy: SharedFlow<Float>
+    val onBackPressed: SharedFlow<Unit>
 
     fun initUIState(instanceState: Bundle)
     fun play()
@@ -45,6 +46,7 @@ interface VideoPlayerViewModel {
     fun nextStream()
     fun switchToFullscreen(embeddedUiConfig: EmbeddedUiConfig)
     fun switchToEmbeddedView()
+    fun onBackPressed()
     fun showUi()
     fun hideUi()
     fun seekPositionChanged(newValue: Float)

new-player/src/main/java/net/newpipe/newplayer/model/VideoPlayerViewModelImpl.kt

@@ -37,6 +37,7 @@ import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.asSharedFlow
 import javax.inject.Inject
 import kotlinx.coroutines.flow.asStateFlow
@@ -127,6 +128,9 @@ class VideoPlayerViewModelImpl @Inject constructor(
     private var mutableEmbeddedPlayerDraggedDownBy = MutableSharedFlow<Float>()
     override val embeddedPlayerDraggedDownBy = mutableEmbeddedPlayerDraggedDownBy.asSharedFlow()
 
+    private var mutableOnBackPressed = MutableSharedFlow<Unit>()
+    override val onBackPressed: SharedFlow<Unit> = mutableOnBackPressed.asSharedFlow()
+
     private fun installNewPlayer() {
         internalPlayer?.let { player ->
             Log.d(TAG, "Install player: ${player.videoSize.width}")
@@ -298,9 +302,7 @@ class VideoPlayerViewModelImpl @Inject constructor(
     }
 
     override fun embeddedDraggedDown(offset: Float) {
-        viewModelScope.launch {
+        saveTryEmit(mutableEmbeddedPlayerDraggedDownBy, offset)
-            mutableEmbeddedPlayerDraggedDownBy.emit(offset)
-        }
     }
 
     override fun fastSeek(count: Int) {
@@ -328,7 +330,6 @@ class VideoPlayerViewModelImpl @Inject constructor(
     }
 
     override fun brightnessChange(changeRate: Float, systemBrightness: Float) {
-
         if (mutableUiState.value.uiMode.fullscreen) {
             val currentBrightness = mutableUiState.value.brightness
                 ?: if (systemBrightness < 0f) 0.5f else systemBrightness
@@ -381,8 +382,16 @@ class VideoPlayerViewModelImpl @Inject constructor(
         updateUiMode(UIModeState.EMBEDDED_VIDEO)
     }
 
+    override fun onBackPressed() {
+        val nextMode = uiState.value.uiMode.getNextModeWhenBackPressed()
+        if (nextMode != null) {
+            updateUiMode(nextMode)
+        } else {
+            saveTryEmit(mutableOnBackPressed, Unit)
+        }
+    }
+
     override fun switchToFullscreen(embeddedUiConfig: EmbeddedUiConfig) {
-        println("gurken fullscreen: ${embeddedUiConfig}")
         uiVisibilityJob?.cancel()
         finishFastSeek()
 
@@ -422,4 +431,12 @@ class VideoPlayerViewModelImpl @Inject constructor(
             }
         }
     }
+
+    private fun <T> saveTryEmit(sharedFlow: MutableSharedFlow<T>, value: T) {
+        if(sharedFlow.tryEmit(value)) {
+            viewModelScope.launch {
+                sharedFlow.emit(value)
+            }
+        }
+    }
 }

new-player/src/main/java/net/newpipe/newplayer/model/ViewoPlayerViewModelDummy.kt

@@ -4,6 +4,7 @@ import android.os.Bundle
 import androidx.media3.common.Player
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.asSharedFlow
 import net.newpipe.newplayer.NewPlayer
 import net.newpipe.newplayer.ui.ContentScale
@@ -16,6 +17,7 @@ open class VideoPlayerViewModelDummy : VideoPlayerViewModel {
     override var maxContentRatio = 16F / 9F
     override var contentFitMode = ContentScale.FIT_INSIDE
     override val embeddedPlayerDraggedDownBy = MutableSharedFlow<Float>().asSharedFlow()
+    override val onBackPressed: SharedFlow<Unit> = MutableSharedFlow<Unit>().asSharedFlow()
 
     override fun initUIState(instanceState: Bundle) {
         println("dummy impl")
@@ -29,6 +31,10 @@ open class VideoPlayerViewModelDummy : VideoPlayerViewModel {
         println("dummy impl")
     }
 
+    override fun onBackPressed() {
+        println("dummy impl")
+    }
+
     override fun switchToFullscreen(embeddedUiConfig: EmbeddedUiConfig) {
         println("dummy impl")
     }

new-player/src/main/java/net/newpipe/newplayer/ui/VideoPlayerControllerUI.kt

@@ -64,19 +64,6 @@ fun VideoPlayerControllerUI(
     viewModel: VideoPlayerViewModel, uiState: VideoPlayerUIState
 ) {
 
-    val context = LocalContext.current
-
-    if (uiState.uiMode.fullscreen) {
-        BackHandler {
-            viewModel.switchToEmbeddedView()
-        }
-    }
-
-    val internalBrightnessChange = { rateChange: Float ->
-        val systemBrightness = getDefaultBrightness(context as Activity)
-        viewModel.brightnessChange(rateChange, systemBrightness)
-    }
-
     val insets = getInsets()
 
     AnimatedVisibility(uiState.uiMode.controllerUiVisible) {

new-player/src/main/java/net/newpipe/newplayer/ui/VideoPlayerUI.kt

@@ -24,6 +24,7 @@ import android.app.Activity
 import android.content.pm.ActivityInfo
 import android.util.Log
 import android.view.SurfaceView
+import androidx.activity.compose.BackHandler
 import androidx.compose.animation.AnimatedVisibility
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.aspectRatio
@@ -105,6 +106,12 @@ fun VideoPlayerUI(
             }
         }
 
+        if (uiState.uiMode.fullscreen) {
+            BackHandler {
+                viewModel.onBackPressed()
+            }
+        }
+
         // setup immersive mode
         LaunchedEffect(
             key1 = uiState.uiMode.systemInsetsVisible,