Handle desync messages

Show them in the chat window and also in a toast during game play.

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/features/netplay/NetplaySession.kt

@@ -95,6 +95,12 @@ class NetplaySession(
     )
     val padBuffer = _padBuffer.asSharedFlow()
 
+    private val _desyncMessages = MutableSharedFlow<NetplayMessage.Desync>(
+        extraBufferCapacity = 32,
+        onBufferOverflow = BufferOverflow.DROP_OLDEST
+    )
+    val desyncMessages = _desyncMessages.asSharedFlow()
+
     private val _saveTransferProgress = MutableStateFlow<SaveTransferProgress?>(null)
     val saveTransferProgress = _saveTransferProgress.asStateFlow()
 
@@ -148,6 +154,7 @@ class NetplaySession(
         game.map { NetplayMessage.GameChanged(it) },
         hostInputAuthorityEnabled.map { NetplayMessage.HostInputAuthorityChanged(it) },
         padBuffer.map { NetplayMessage.BufferChanged(it) },
+        desyncMessages,
     )
 
     private fun releaseNativeResources() {
@@ -236,6 +243,11 @@ class NetplaySession(
         _padBuffer.tryEmit(buffer)
     }
 
+    @Keep
+    fun onDesync(frame: Int, player: String) {
+        _desyncMessages.tryEmit(NetplayMessage.Desync(player, frame))
+    }
+
     @Keep
     fun onShowChunkedProgressDialog(title: String, dataSize: Long, playerIds: IntArray) {
         val players = _players.replayCache.firstOrNull()

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/features/netplay/model/NetplayMessage.kt

@@ -26,4 +26,9 @@ sealed class NetplayMessage {
         override fun message(context: Context) =
             context.getString(R.string.netplay_message_buffer_changed, buffer)
     }
+
+    class Desync(private val player: String, private val frame: Int) : NetplayMessage() {
+        override fun message(context: Context) =
+            context.getString(R.string.netplay_message_desync, player, frame)
+    }
 }

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/fragments/EmulationFragment.kt

@@ -9,9 +9,12 @@ import android.view.LayoutInflater
 import android.view.SurfaceHolder
 import android.view.View
 import android.view.ViewGroup
+import android.widget.Toast
 import androidx.fragment.app.Fragment
 import androidx.lifecycle.lifecycleScope
 import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
 import org.dolphinemu.dolphinemu.NativeLibrary
 import org.dolphinemu.dolphinemu.activities.EmulationActivity
@@ -231,6 +234,10 @@ class EmulationFragment : Fragment(), SurfaceHolder.Callback {
                         netplaySession.stopGame.first()
                         stopEmulation()
                     }
+                    netplaySession
+                        .desyncMessages
+                        .onEach { Toast.makeText(requireContext(), it.message(requireContext()), Toast.LENGTH_SHORT).show() }
+                        .launchIn(lifecycleScope)
                     NativeLibrary.RunNetPlay(
                         paths,
                         riivolution,

Source/Android/app/src/main/res/values/strings.xml

@@ -1002,6 +1002,7 @@ It can efficiently compress both junk data and encrypted Wii data.
     <string name="netplay_message_game_changed">Game changed to %1$s</string>
     <string name="netplay_message_buffer_changed">Buffer size changed to %1$d</string>
     <string name="netplay_message_host_input_authority_changed">"Host input authority %1$s"</string>
+    <string name="netplay_message_desync">Possible desync detected: %1$s might have desynced at frame %2$d</string>
     <string name="netplay_game_label">Game</string>
     <string name="netplay_players_label">Players</string>
     <string name="netplay_players_name">Name</string>