Android: Fix emulation stopping on app switch and UI covering display

android/app/src/cpp/android_host_interface.cpp

@@ -162,6 +162,11 @@ void AndroidHostInterface::UpdateInputMap()
   CommonHostInterface::UpdateInputMap(m_settings_interface);
 }
 
+bool AndroidHostInterface::IsEmulationThreadPaused() const
+{
+  return System::IsValid() && System::IsPaused();
+}
+
 bool AndroidHostInterface::StartEmulationThread(jobject emulation_activity, ANativeWindow* initial_surface,
                                                 SystemBootParameters boot_params, bool resume_state)
 {
@@ -176,11 +181,23 @@ bool AndroidHostInterface::StartEmulationThread(jobject emulation_activity, ANat
   return true;
 }
 
+void AndroidHostInterface::PauseEmulationThread(bool paused)
+{
+  Assert(IsEmulationThreadRunning());
+  RunOnEmulationThread([this, paused]() {
+    PauseSystem(paused);
+  });
+}
+
 void AndroidHostInterface::StopEmulationThread()
 {
   Assert(IsEmulationThreadRunning());
   Log_InfoPrint("Stopping emulation thread...");
-  m_emulation_thread_stop_request.store(true);
+  {
+    std::unique_lock<std::mutex> lock(m_mutex);
+    m_emulation_thread_stop_request.store(true);
+    m_sleep_cv.notify_one();
+  }
   m_emulation_thread.join();
   Log_InfoPrint("Emulation thread stopped");
 }
@@ -193,8 +210,9 @@ void AndroidHostInterface::RunOnEmulationThread(std::function<void()> function,
     return;
   }
 
-  m_callback_mutex.lock();
+  m_mutex.lock();
   m_callback_queue.push_back(std::move(function));
+  m_sleep_cv.notify_one();
 
   if (blocking)
   {
@@ -204,12 +222,12 @@ void AndroidHostInterface::RunOnEmulationThread(std::function<void()> function,
       if (m_callback_queue.empty())
         break;
 
-      m_callback_mutex.unlock();
-      m_callback_mutex.lock();
+      m_mutex.unlock();
+      m_mutex.lock();
     }
   }
 
-  m_callback_mutex.unlock();
+  m_mutex.unlock();
 }
 
 void AndroidHostInterface::EmulationThreadEntryPoint(jobject emulation_activity, ANativeWindow* initial_surface,
@@ -254,22 +272,44 @@ void AndroidHostInterface::EmulationThreadEntryPoint(jobject emulation_activity,
 
   // System is ready to go.
   thread_env->CallVoidMethod(m_emulation_activity_object, s_EmulationActivity_method_onEmulationStarted);
-  while (!m_emulation_thread_stop_request.load())
+  EmulationThreadLoop();
+
+  thread_env->CallVoidMethod(m_emulation_activity_object, s_EmulationActivity_method_onEmulationStopped);
+  PowerOffSystem();
+  DestroyImGuiContext();
+  thread_env->DeleteGlobalRef(m_emulation_activity_object);
+  m_emulation_activity_object = {};
+  s_jvm->DetachCurrentThread();
+}
+
+void AndroidHostInterface::EmulationThreadLoop()
+{
+  for (;;)
   {
     // run any events
-    m_callback_mutex.lock();
-    for (;;)
     {
-      if (m_callback_queue.empty())
-        break;
+      std::unique_lock<std::mutex> lock(m_mutex);
+      for (;;) {
+        while (!m_callback_queue.empty()) {
+          auto callback = std::move(m_callback_queue.front());
+          m_callback_queue.pop_front();
+          lock.unlock();
+          callback();
+          lock.lock();
+        }
 
-      auto callback = std::move(m_callback_queue.front());
-      m_callback_queue.pop_front();
-      m_callback_mutex.unlock();
-      callback();
-      m_callback_mutex.lock();
+        if (m_emulation_thread_stop_request.load())
+          return;
+
+        if (System::IsPaused()) {
+          // paused, wait for us to resume
+          m_sleep_cv.wait(lock);
+        } else {
+          // done with callbacks, run the frame
+          break;
+        }
+      }
     }
-    m_callback_mutex.unlock();
 
     // simulate the system if not paused
     if (System::IsRunning())
@@ -291,13 +331,6 @@ void AndroidHostInterface::EmulationThreadEntryPoint(jobject emulation_activity,
       }
     }
   }
-
-  thread_env->CallVoidMethod(m_emulation_activity_object, s_EmulationActivity_method_onEmulationStopped);
-  PowerOffSystem();
-  DestroyImGuiContext();
-  thread_env->DeleteGlobalRef(m_emulation_activity_object);
-  m_emulation_activity_object = {};
-  s_jvm->DetachCurrentThread();
 }
 
 bool AndroidHostInterface::AcquireHostDisplay()
@@ -373,7 +406,7 @@ void AndroidHostInterface::SurfaceChanged(ANativeWindow* surface, int format, in
   if (m_display)
   {
     WindowInfo wi;
-    wi.type = WindowInfo::Type::Android;
+    wi.type = surface ? WindowInfo::Type::Android : WindowInfo::Type::Surfaceless;
     wi.window_handle = surface;
     wi.surface_width = width;
     wi.surface_height = height;
@@ -588,8 +621,8 @@ DEFINE_JNI_ARGS_METHOD(void, AndroidHostInterface_stopEmulationThread, jobject o
 DEFINE_JNI_ARGS_METHOD(void, AndroidHostInterface_surfaceChanged, jobject obj, jobject surface, jint format, jint width,
                        jint height)
 {
-  ANativeWindow* native_surface = ANativeWindow_fromSurface(env, surface);
-  if (!native_surface)
+  ANativeWindow* native_surface = surface ? ANativeWindow_fromSurface(env, surface) : nullptr;
+  if (surface && !native_surface)
     Log_ErrorPrint("ANativeWindow_fromSurface() returned null");
 
   AndroidHostInterface* hi = AndroidHelpers::GetNativeClass(env, obj);
@@ -724,9 +757,39 @@ DEFINE_JNI_ARGS_METHOD(void, AndroidHostInterface_saveState, jobject obj, jboole
   hi->RunOnEmulationThread([hi, global, slot]() { hi->SaveState(global, slot); });
 }
 
+DEFINE_JNI_ARGS_METHOD(void, AndroidHostInterface_saveResumeState, jobject obj, jboolean wait_for_completion)
+{
+  AndroidHostInterface* hi = AndroidHelpers::GetNativeClass(env, obj);
+  hi->RunOnEmulationThread([hi]() { hi->SaveResumeSaveState(); }, wait_for_completion);
+}
+
 DEFINE_JNI_ARGS_METHOD(void, AndroidHostInterface_setDisplayAlignment, jobject obj, jint alignment)
 {
   AndroidHostInterface* hi = AndroidHelpers::GetNativeClass(env, obj);
   hi->RunOnEmulationThread([hi, alignment]() { hi->GetDisplay()->SetDisplayAlignment(static_cast<HostDisplay::Alignment>(alignment)); });
 }
 
+DEFINE_JNI_ARGS_METHOD(bool, AndroidHostInterface_hasSurface, jobject obj)
+{
+  AndroidHostInterface* hi = AndroidHelpers::GetNativeClass(env, obj);
+  HostDisplay* display = hi->GetDisplay();
+  if (display)
+    return display->HasRenderSurface();
+  else
+    return false;
+}
+
+DEFINE_JNI_ARGS_METHOD(bool, AndroidHostInterface_isEmulationThreadPaused, jobject obj)
+{
+  AndroidHostInterface* hi = AndroidHelpers::GetNativeClass(env, obj);
+  return hi->IsEmulationThreadPaused();
+}
+
+DEFINE_JNI_ARGS_METHOD(void, AndroidHostInterface_pauseEmulationThread, jobject obj, jboolean paused)
+{
+  AndroidHostInterface* hi = AndroidHelpers::GetNativeClass(env, obj);
+  hi->PauseEmulationThread(paused);
+}
+
+
+

android/app/src/cpp/android_host_interface.h

@@ -4,6 +4,7 @@
 #include "frontend-common/common_host_interface.h"
 #include <array>
 #include <atomic>
+#include <condition_variable>
 #include <functional>
 #include <jni.h>
 #include <memory>
@@ -35,9 +36,11 @@ public:
   float GetFloatSettingValue(const char* section, const char* key, float default_value = 0.0f) override;
 
   bool IsEmulationThreadRunning() const { return m_emulation_thread.joinable(); }
+  bool IsEmulationThreadPaused() const;
   bool StartEmulationThread(jobject emulation_activity, ANativeWindow* initial_surface,
                             SystemBootParameters boot_params, bool resume_state);
   void RunOnEmulationThread(std::function<void()> function, bool blocking = false);
+  void PauseEmulationThread(bool paused);
   void StopEmulationThread();
 
   void SurfaceChanged(ANativeWindow* surface, int format, int width, int height);
@@ -63,6 +66,7 @@ protected:
 private:
   void EmulationThreadEntryPoint(jobject emulation_activity, ANativeWindow* initial_surface,
                                  SystemBootParameters boot_params, bool resume_state);
+  void EmulationThreadLoop();
 
   void CreateImGuiContext();
   void DestroyImGuiContext();
@@ -74,7 +78,8 @@ private:
 
   ANativeWindow* m_surface = nullptr;
 
-  std::mutex m_callback_mutex;
+  std::mutex m_mutex;
+  std::condition_variable m_sleep_cv;
   std::deque<std::function<void()>> m_callback_queue;
 
   std::thread m_emulation_thread;

android/app/src/main/java/com/github/stenzek/duckstation/AndroidHostInterface.java

@@ -34,8 +34,14 @@ public class AndroidHostInterface {
 
     public native boolean startEmulationThread(EmulationActivity emulationActivity, Surface surface, String filename, boolean resumeState, String state_filename);
 
+    public native boolean isEmulationThreadPaused();
+
+    public native void pauseEmulationThread(boolean paused);
+
     public native void stopEmulationThread();
 
+    public native boolean hasSurface();
+
     public native void surfaceChanged(Surface surface, int format, int width, int height);
 
     // TODO: Find a better place for this.
@@ -59,6 +65,8 @@ public class AndroidHostInterface {
 
     public native void saveState(boolean global, int slot);
 
+    public native void saveResumeState(boolean waitForCompletion);
+
     public native void applySettings();
 
     public native void setDisplayAlignment(int alignment);

android/app/src/main/java/com/github/stenzek/duckstation/EmulationActivity.java

@@ -3,6 +3,7 @@ package com.github.stenzek.duckstation;
 import android.annotation.SuppressLint;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.appcompat.app.ActionBar;
 import androidx.appcompat.app.AlertDialog;
 import androidx.appcompat.app.AppCompatActivity;
@@ -12,6 +13,7 @@ import android.content.SharedPreferences;
 import android.content.res.Configuration;
 import android.os.Bundle;
 import android.os.Handler;
+import android.util.AndroidException;
 import android.util.Log;
 import android.view.Menu;
 import android.view.SurfaceHolder;
@@ -30,7 +32,10 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
     /**
      * Settings interfaces.
      */
-    SharedPreferences mPreferences;
+    private SharedPreferences mPreferences;
+    private boolean mWasDestroyed = false;
+    private boolean mWasPausedOnSurfaceLoss = false;
+    private boolean mApplySettingsOnSurfaceRestored = false;
 
     private boolean getBooleanSetting(String key, boolean defaultValue) {
         return mPreferences.getBoolean(key, defaultValue);
@@ -85,7 +90,8 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
 
     public void onEmulationStopped() {
         runOnUiThread(() -> {
-            finish();
+            if (!mWasDestroyed)
+                finish();
         });
     }
 
@@ -95,6 +101,16 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
         });
     }
 
+    private void applySettings() {
+        if (!AndroidHostInterface.getInstance().isEmulationThreadRunning())
+            return;
+
+        if (AndroidHostInterface.getInstance().hasSurface())
+            AndroidHostInterface.getInstance().applySettings();
+        else
+            mApplySettingsOnSurfaceRestored = true;
+    }
+
     @Override
     public void surfaceCreated(SurfaceHolder holder) {
     }
@@ -103,8 +119,19 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
     public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
         // Once we get a surface, we can boot.
         if (AndroidHostInterface.getInstance().isEmulationThreadRunning()) {
+            final boolean hadSurface = AndroidHostInterface.getInstance().hasSurface();
             AndroidHostInterface.getInstance().surfaceChanged(holder.getSurface(), format, width, height);
             updateOrientation();
+
+            if (holder.getSurface() != null && !hadSurface && AndroidHostInterface.getInstance().isEmulationThreadPaused() && !mWasPausedOnSurfaceLoss) {
+                AndroidHostInterface.getInstance().pauseEmulationThread(false);
+            }
+
+            if (mApplySettingsOnSurfaceRestored) {
+                AndroidHostInterface.getInstance().applySettings();
+                mApplySettingsOnSurfaceRestored = false;
+            }
+
             return;
         }
 
@@ -121,14 +148,21 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
         if (!AndroidHostInterface.getInstance().isEmulationThreadRunning())
             return;
 
-        Log.i("EmulationActivity", "Stopping emulation thread");
-        AndroidHostInterface.getInstance().stopEmulationThread();
+        Log.i("EmulationActivity", "Surface destroyed");
+
+        // Save the resume state in case we never get back again...
+        AndroidHostInterface.getInstance().saveResumeState(true);
+
+        mWasPausedOnSurfaceLoss = AndroidHostInterface.getInstance().isEmulationThreadPaused();
+        AndroidHostInterface.getInstance().pauseEmulationThread(true);
+        AndroidHostInterface.getInstance().surfaceChanged(null, 0, 0, 0);
     }
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         mPreferences = PreferenceManager.getDefaultSharedPreferences(this);
+        Log.i("EmulationActivity", "OnCreate");
 
         setContentView(R.layout.activity_emulation);
         ActionBar actionBar = getSupportActionBar();
@@ -167,10 +201,20 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
     }
 
     @Override
-    protected void onStop() {
-        super.onStop();
+    protected void onPostResume() {
+        super.onPostResume();
+        if (!mSystemUIVisible)
+            hideSystemUI();
+    }
+
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
+        Log.i("EmulationActivity", "OnStop");
+        showSystemUI(false);
 
         if (AndroidHostInterface.getInstance().isEmulationThreadRunning()) {
+            mWasDestroyed = true;
             AndroidHostInterface.getInstance().stopEmulationThread();
         }
     }
@@ -185,6 +229,8 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
         return true;
     }
 
+    private static final int REQUEST_CODE_SETTINGS = 0;
+
     @Override
     public boolean onOptionsItemSelected(MenuItem item) {
         // Handle action bar item clicks here. The action bar will
@@ -195,7 +241,8 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
         //noinspection SimplifiableIfStatement
         if (id == R.id.action_settings) {
             Intent intent = new Intent(this, SettingsActivity.class);
-            startActivity(intent);
+            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
+            startActivityForResult(intent, REQUEST_CODE_SETTINGS);
             return true;
         } else if (id == R.id.show_controller) {
             setTouchscreenControllerVisibility(!mTouchscreenControllerVisible);
@@ -205,7 +252,7 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
             boolean newSetting = !getBooleanSetting("Main/SpeedLimiterEnabled", true);
             setBooleanSetting("Main/SpeedLimiterEnabled", newSetting);
             item.setChecked(newSetting);
-            AndroidHostInterface.getInstance().applySettings();
+            applySettings();
             return true;
         } else if (id == R.id.reset) {
             AndroidHostInterface.getInstance().resetSystem();
@@ -221,6 +268,17 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
         return super.onOptionsItemSelected(item);
     }
 
+    @Override
+    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
+        super.onActivityResult(requestCode, resultCode, data);
+
+        if (requestCode == REQUEST_CODE_SETTINGS) {
+            // TODO: Sync any menu settings.
+            if (AndroidHostInterface.getInstance().isEmulationThreadRunning())
+                applySettings();
+        }
+    }
+
     @Override
     public void onBackPressed() {
         if (mSystemUIVisible) {
@@ -228,7 +286,7 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
             return;
         }
 
-        showSystemUI();
+        showSystemUI(true);
     }
 
     @Override
@@ -308,24 +366,17 @@ public class EmulationActivity extends AppCompatActivity implements SurfaceHolde
     }
 
     @SuppressLint("InlinedApi")
-    private void showSystemUI() {
+    private void showSystemUI(boolean delay) {
         // Show the system bar
-        mContentView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
-                | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);
+        mContentView.setSystemUiVisibility(0);
         mSystemUIVisible = true;
 
         // Schedule a runnable to display UI elements after a delay
         mSystemUIHideHandler.removeCallbacks(mHidePart2Runnable);
-        mSystemUIHideHandler.postDelayed(mShowPart2Runnable, UI_ANIMATION_DELAY);
-    }
-
-    /**
-     * Schedules a call to hide() in delay milliseconds, canceling any
-     * previously scheduled calls.
-     */
-    private void delayedHide(int delayMillis) {
-        mSystemUIHideHandler.removeCallbacks(mHideRunnable);
-        mSystemUIHideHandler.postDelayed(mHideRunnable, delayMillis);
+        if (delay)
+            mSystemUIHideHandler.postDelayed(mShowPart2Runnable, UI_ANIMATION_DELAY);
+        else
+            mShowPart2Runnable.run();
     }
 
     /**