resolve potential deadlocks (#66)

A deadlock could occur if the save callback is called just before the frontend set functions are used.
Thus unlock() is necessary before setting current scene or transition.
(e.g. if start recording is activated just before using the above functions, as this apparently triggers a save() call)

src/advanced-scene-switcher.cpp

@@ -335,6 +335,8 @@ void SwitcherData::Thread()
 		bool match = false;
 		OBSWeakSource scene;
 		OBSWeakSource transition;
+		bool defTransitionMatch = false;
+		OBSWeakSource defTransition;
 		std::chrono::milliseconds duration;
 		if (sleep > interval) {
 			duration = std::chrono::milliseconds(sleep);
@@ -354,8 +356,6 @@ void SwitcherData::Thread()
 			break;
 		}
 
-		setDefaultSceneTransitions();
-
 		if (autoStopEnable) {
 			autoStopStreamAndRecording();
 		}
@@ -368,6 +368,8 @@ void SwitcherData::Thread()
 			continue;
 		}
 
+		checkDefaultSceneTransitions(defTransitionMatch, defTransition);
+
 		for (int switchFuncName : functionNamesByPriority) {
 			switch (switchFuncName) {
 			case read_file_func:
@@ -422,9 +424,22 @@ void SwitcherData::Thread()
 		if (!match && switchIfNotMatching == RANDOM_SWITCH) {
 			checkRandom(match, scene, transition, sleep);
 		}
+
+		// After this point we will call frontend functions
+		// obs_frontend_set_current_scene() and
+		// obs_frontend_set_current_transition()
+		//
+		// During this time SaveSceneSwitcher() could be called
+		// leading to a deadlock, so we have to unlock()
+		lock.unlock();
+
+		if (!match && defTransitionMatch) {
+			setCurrentDefTransition(defTransition);
+		}
+
 		if (match) {
 			switchScene(scene, transition,
-				    tansitionOverrideOverride, lock);
+				    tansitionOverrideOverride);
 		}
 	}
 endLoop:
@@ -432,8 +447,7 @@ endLoop:
 }
 
 void switchScene(OBSWeakSource &scene, OBSWeakSource &transition,
-		 bool &transitionOverrideOverride,
-		 std::unique_lock<std::mutex> &lock)
+		 bool &transitionOverrideOverride)
 {
 	obs_source_t *source = obs_weak_source_get_source(scene);
 	obs_source_t *currentSource = obs_frontend_get_current_scene();
@@ -453,18 +467,6 @@ void switchScene(OBSWeakSource &scene, OBSWeakSource &transition,
 	obs_source_release(source);
 }
 
-bool SwitcherData::sceneChangedDuringWait()
-{
-	bool r = false;
-	obs_source_t *currentSource = obs_frontend_get_current_scene();
-	if (!currentSource)
-		return true;
-	obs_source_release(currentSource);
-	if (waitScene && currentSource != waitScene)
-		r = true;
-	return r;
-}
-
 void SwitcherData::Start()
 {
 	if (!(th && th->isRunning())) {
@@ -487,6 +489,15 @@ void SwitcherData::Stop()
 	}
 }
 
+bool SwitcherData::sceneChangedDuringWait()
+{
+	obs_source_t *currentSource = obs_frontend_get_current_scene();
+	if (!currentSource)
+		return true;
+	obs_source_release(currentSource);
+	return (waitScene && currentSource != waitScene);
+}
+
 /********************************************************************************
  * OBS module setup
  ********************************************************************************/
@@ -521,7 +532,11 @@ void handleSceneChange(SwitcherData *s)
 
 	//reset events only hanled on scene change
 	s->autoStartedRecently = false;
-	s->changedDefTransitionRecently = false;
+}
+
+void handleTransitionStop(SwitcherData *s)
+{
+	s->checkedDefTransition = false;
 }
 
 void setLiveTime(SwitcherData *s)
@@ -546,6 +561,9 @@ static void OBSEvent(enum obs_frontend_event event, void *switcher)
 	case OBS_FRONTEND_EVENT_SCENE_CHANGED:
 		handleSceneChange((SwitcherData *)switcher);
 		break;
+	case OBS_FRONTEND_EVENT_TRANSITION_STOPPED:
+		handleTransitionStop((SwitcherData *)switcher);
+		break;
 	case OBS_FRONTEND_EVENT_RECORDING_STARTED:
 	case OBS_FRONTEND_EVENT_STREAMING_STARTED:
 		setLiveTime((SwitcherData *)switcher);

src/headers/advanced-scene-switcher.hpp

@@ -228,10 +228,8 @@ void setNextTransition(OBSWeakSource &targetScene, obs_source_t *currentSource,
 void overwriteTransitionOverride(obs_weak_source_t *sceneWs,
 				 obs_source_t *transition, transitionData &td);
 void restoreTransitionOverride(obs_source_t *scene, transitionData td);
-
 void switchScene(OBSWeakSource &scene, OBSWeakSource &transition,
-		 bool &transitionOverrideOverride,
-		 std::unique_lock<std::mutex> &lock);
+		 bool &transitionOverrideOverride);
 
 /********************************************************************************
  * Main SwitcherData

src/headers/switcher-data-structs.hpp

@@ -99,7 +99,7 @@ struct SwitcherData {
 
 	std::deque<SceneTransition> sceneTransitions;
 	std::deque<DefaultSceneTransition> defaultSceneTransitions;
-	bool changedDefTransitionRecently = false;
+	bool checkedDefTransition = false;
 
 	std::deque<MediaSwitch> mediaSwitches;
 
@@ -154,10 +154,12 @@ struct SwitcherData {
 	bool sceneChangedDuringWait();
 	bool prioFuncsValid();
 	void writeSceneInfoToFile();
-	void setDefaultSceneTransitions();
 	void autoStopStreamAndRecording();
 	void autoStartStreamRecording();
 	bool checkPause();
+	void checkDefaultSceneTransitions(bool &match,
+					  OBSWeakSource &transition);
+	void setCurrentDefTransition(OBSWeakSource &transition);
 	void checkSceneSequence(bool &match, OBSWeakSource &scene,
 				OBSWeakSource &transition,
 				std::unique_lock<std::mutex> &lock);

src/switch-transitions.cpp

@@ -143,9 +143,10 @@ void AdvSceneSwitcher::on_defaultTransitionsDown_clicked()
 		  switcher->defaultSceneTransitions[index + 1]);
 }
 
-void SwitcherData::setDefaultSceneTransitions()
+void SwitcherData::checkDefaultSceneTransitions(bool &match,
+						OBSWeakSource &transition)
 {
-	if (changedDefTransitionRecently)
+	if (checkedDefTransition)
 		return;
 
 	obs_source_t *currentSource = obs_frontend_get_current_scene();
@@ -156,22 +157,25 @@ void SwitcherData::setDefaultSceneTransitions()
 			if (!s.initialized())
 				continue;
 
-			obs_source_t *transition =
-				obs_weak_source_get_source(s.transition);
-			//This might cancel the current transition
-			//There is no way to be sure when the previous transition finished
-			obs_frontend_set_current_transition(transition);
+			match = true;
+			transition = s.transition;
 
 			if (verbose)
 				s.logMatch();
-
-			obs_source_release(transition);
 			break;
 		}
 	}
 	obs_source_release(currentSource);
 	obs_weak_source_release(ws);
-	changedDefTransitionRecently = true;
+
+	checkedDefTransition = true;
+}
+
+void SwitcherData::setCurrentDefTransition(OBSWeakSource &transition)
+{
+	obs_source_t *transitionSource = obs_weak_source_get_source(transition);
+	obs_frontend_set_current_transition(transitionSource);
+	obs_source_release(transitionSource);
 }
 
 void AdvSceneSwitcher::on_transitionOverridecheckBox_stateChanged(int state)