Fix deadlock on exit if SKIP_FRAMES disabled

On exit, the renderer will not consume frames anymore, so signal the
condition variable to wake up the decoder.

app/src/decoder.c

@@ -152,6 +152,10 @@ SDL_bool decoder_start(struct decoder *decoder) {
     return SDL_TRUE;
 }
 
+void decoder_stop(struct decoder *decoder) {
+    frames_stop(decoder->frames);
+}
+
 void decoder_join(struct decoder *decoder) {
     SDL_WaitThread(decoder->thread, NULL);
 }

app/src/decoder.h

@@ -14,6 +14,7 @@ struct decoder {
 };
 
 SDL_bool decoder_start(struct decoder *decoder);
+void decoder_stop(struct decoder *decoder);
 void decoder_join(struct decoder *decoder);
 
 #endif

app/src/frames.c

@@ -27,6 +27,7 @@ SDL_bool frames_init(struct frames *frames) {
         SDL_DestroyMutex(frames->mutex);
         goto error_2;
     }
+    frames->stopped = SDL_FALSE;
 #endif
 
     // there is initially no rendering frame, so consider it has already been
@@ -60,24 +61,23 @@ static void frames_swap(struct frames *frames) {
 
 SDL_bool frames_offer_decoded_frame(struct frames *frames) {
     mutex_lock(frames->mutex);
-    SDL_bool previous_frame_consumed;
 #ifndef SKIP_FRAMES
     // if SKIP_FRAMES is disabled, then the decoder must wait for the current
     // frame to be consumed
-    while (!frames->rendering_frame_consumed) {
+    while (!frames->rendering_frame_consumed && !frames->stopped) {
         cond_wait(frames->rendering_frame_consumed_cond, frames->mutex);
     }
-    // by definition, we are not skipping the frames
-    previous_frame_consumed = SDL_TRUE;
 #else
-    previous_frame_consumed = frames->rendering_frame_consumed;
-    if (!previous_frame_consumed) {
+    if (!frames->rendering_frame_consumed) {
         SDL_LogDebug(SDL_LOG_CATEGORY_RENDER, "Skip frame");
     }
 #endif
 
     frames_swap(frames);
+
+    SDL_bool previous_frame_consumed = frames->rendering_frame_consumed;
     frames->rendering_frame_consumed = SDL_FALSE;
+
     mutex_unlock(frames->mutex);
     return previous_frame_consumed;
 }
@@ -92,3 +92,15 @@ const AVFrame *frames_consume_rendered_frame(struct frames *frames) {
 #endif
     return frames->rendering_frame;
 }
+
+void frames_stop(struct frames *frames) {
+#ifdef SKIP_FRAMES
+    (void) frames; // unused
+#else
+    mutex_lock(frames->mutex);
+    frames->stopped = SDL_TRUE;
+    mutex_unlock(frames->mutex);
+    // wake up blocking wait
+    cond_signal(frames->rendering_frame_consumed_cond);
+#endif
+}

app/src/frames.h

@@ -14,6 +14,7 @@ struct frames {
     AVFrame *rendering_frame;
     SDL_mutex *mutex;
 #ifndef SKIP_FRAMES
+    SDL_bool stopped;
     SDL_cond *rendering_frame_consumed_cond;
 #endif
     SDL_bool rendering_frame_consumed;
@@ -33,4 +34,7 @@ SDL_bool frames_offer_decoded_frame(struct frames *frames);
 // unlocking frames->mutex
 const AVFrame *frames_consume_rendered_frame(struct frames *frames);
 
+// wake up and avoid any blocking call
+void frames_stop(struct frames *frames);
+
 #endif

app/src/scrcpy.c

@@ -180,6 +180,7 @@ finally_stop_and_join_controller:
 finally_destroy_controller:
     controller_destroy(&controller);
 finally_stop_decoder:
+    decoder_stop(&decoder);
     // kill the server before decoder_join() to wake up the decoder
     server_stop(&server, serial);
     decoder_join(&decoder);