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()
 
@@ -146,6 +152,7 @@ class NetplaySession(
         game.map { NetplayMessage.GameChanged(it) },
         hostInputAuthorityEnabled.map { NetplayMessage.HostInputAuthorityChanged(it) },
         padBuffer.map { NetplayMessage.BufferChanged(it) },
+        desyncMessages,
     )
 
     private fun releaseNativeResources() {
@@ -234,6 +241,11 @@ 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>

Source/Android/jni/AndroidCommon/IDCache.cpp

@@ -43,6 +43,7 @@ static jmethodID s_netplay_update;
 static jmethodID s_netplay_on_show_chunked_progress_dialog;
 static jmethodID s_netplay_on_set_chunked_progress;
 static jmethodID s_netplay_on_hide_chunked_progress_dialog;
+static jmethodID s_netplay_on_desync;
 
 static jclass s_netplay_player_class;
 static jmethodID s_netplay_player_constructor;
@@ -327,6 +328,11 @@ jmethodID GetNetplayOnHideChunkedProgressDialog()
   return s_netplay_on_hide_chunked_progress_dialog;
 }
 
+jmethodID GetNetplayOnDesync()
+{
+  return s_netplay_on_desync;
+}
+
 jclass GetNetplayPlayerClass()
 {
   return s_netplay_player_class;
@@ -766,6 +772,8 @@ JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved)
       env->GetMethodID(netplay_class, "onSetChunkedProgress", "(IJ)V");
   s_netplay_on_hide_chunked_progress_dialog =
       env->GetMethodID(netplay_class, "onHideChunkedProgressDialog", "()V");
+  s_netplay_on_desync =
+      env->GetMethodID(netplay_class, "onDesync", "(ILjava/lang/String;)V");
   env->DeleteLocalRef(netplay_class);
 
   const jclass netplay_player_class =

Source/Android/jni/AndroidCommon/IDCache.h

@@ -46,6 +46,7 @@ jmethodID GetNetplayUpdate();
 jmethodID GetNetplayOnShowChunkedProgressDialog();
 jmethodID GetNetplayOnSetChunkedProgress();
 jmethodID GetNetplayOnHideChunkedProgressDialog();
+jmethodID GetNetplayOnDesync();
 
 jclass GetNetplayPlayerClass();
 jmethodID GetNetplayPlayerConstructor();

Source/Android/jni/NetPlay/NetPlayUICallbacks.cpp

@@ -197,7 +197,17 @@ void NetPlayUICallbacks::OnHostInputAuthorityChanged(bool enabled)
   env->DeleteLocalRef(netplay_session);
 }
 
-void NetPlayUICallbacks::OnDesync(u32, const std::string&) {}
+void NetPlayUICallbacks::OnDesync(u32 frame, const std::string& player)
+{
+  JNIEnv* env = IDCache::GetEnvForThread();
+  jobject netplay_session = GetNetplaySessionLocalRef(env);
+  if (!netplay_session)
+    return;
+
+  env->CallVoidMethod(netplay_session, IDCache::GetNetplayOnDesync(),
+                      static_cast<jint>(frame), ToJString(env, player));
+  env->DeleteLocalRef(netplay_session);
+}
 
 void NetPlayUICallbacks::OnConnectionLost()
 {