Frontend_API: Expose Studio mode:"Swap preview/program after transitioning" via the frontend API

docs/sphinx/reference-frontend-api.rst

@@ -167,6 +167,11 @@ Structures/Enumerations
      Triggered when the current preview scene has changed in studio
      mode.
 
+   - **OBS_FRONTEND_EVENT_SWAP_SCENES_MODE_CHANGED**
+
+     Triggered when the "Swap preview/program scenes after transitioning"
+     option in studio mode is toggled
+
    - **OBS_FRONTEND_EVENT_SCENE_COLLECTION_CLEANUP**
 
      Triggered when a scene collection has been completely unloaded, and
@@ -820,6 +825,26 @@ Functions
 
 ---------------------------------------
 
+.. function:: obs_frontend_set_swap_scenes_mode(bool enable)
+
+   Toggles the "Swap preview/program scenes after transitioning"
+   behavior while in studio mode. Useful for instances where
+   both behaviors may be desirable depending on circumstance.
+   Does nothing when not using studio mode.
+
+   :param enable: *true* to enable this mode, *false* to disable it
+
+---------------------------------------
+
+.. function:: obs_frontend_get_swap_scenes_mode(void)
+
+   Get the current value of "Swap preview/program scenes after transitioning"
+   option in studio mode.
+
+   :return: *true* if mode is enabled, *false* otherwise
+
+---------------------------------------
+
 .. function:: void *obs_frontend_take_screenshot(void)
 
    Takes a screenshot of the main OBS output.

frontend/OBSStudioAPI.cpp

@@ -565,6 +565,21 @@ void OBSStudioAPI::obs_frontend_set_current_preview_scene(obs_source_t *scene)
 					  Q_ARG(bool, false));
 	}
 }
+bool OBSStudioAPI::obs_frontend_get_swap_scenes_mode(void)
+{
+	OBSBasic *main = OBSBasic::Get();
+	if (!main)
+		return false;
+	return main->GetSwapScenesMode();
+}
+
+void OBSStudioAPI::obs_frontend_set_swap_scenes_mode(bool enabled)
+{
+	OBSBasic *main = OBSBasic::Get();
+	if (!main)
+		return;
+	main->SetSwapScenesMode(enabled);
+}
 
 void OBSStudioAPI::obs_frontend_take_screenshot()
 {

frontend/OBSStudioAPI.hpp

@@ -183,6 +183,10 @@ struct OBSStudioAPI : obs_frontend_callbacks {
 
 	void obs_frontend_set_current_preview_scene(obs_source_t *scene) override;
 
+	bool obs_frontend_get_swap_scenes_mode(void) override;
+
+	void obs_frontend_set_swap_scenes_mode(bool enabled) override;
+
 	void obs_frontend_take_screenshot(void) override;
 
 	void obs_frontend_take_source_screenshot(obs_source_t *source) override;

frontend/api/obs-frontend-api.cpp

@@ -504,6 +504,19 @@ void obs_frontend_take_source_screenshot(obs_source_t *source)
 		c->obs_frontend_take_source_screenshot(source);
 }
 
+bool obs_frontend_get_swap_scenes_mode(void)
+{
+	if (callbacks_valid())
+		return c->obs_frontend_get_swap_scenes_mode();
+	return false;
+}
+
+void obs_frontend_set_swap_scenes_mode(bool enabled)
+{
+	if (callbacks_valid())
+		c->obs_frontend_set_swap_scenes_mode(enabled);
+}
+
 obs_output_t *obs_frontend_get_virtualcam_output(void)
 {
 	return !!callbacks_valid() ? c->obs_frontend_get_virtualcam_output() : nullptr;

frontend/api/obs-frontend-api.h

@@ -65,6 +65,7 @@ enum obs_frontend_event {
 
 	OBS_FRONTEND_EVENT_CANVAS_ADDED,
 	OBS_FRONTEND_EVENT_CANVAS_REMOVED,
+	OBS_FRONTEND_EVENT_SWAP_SCENES_MODE_CHANGED,
 };
 
 /* ------------------------------------------------------------------------- */
@@ -222,6 +223,9 @@ EXPORT bool obs_frontend_preview_enabled(void);
 EXPORT obs_source_t *obs_frontend_get_current_preview_scene(void);
 EXPORT void obs_frontend_set_current_preview_scene(obs_source_t *scene);
 
+EXPORT bool obs_frontend_get_swap_scenes_mode(void);
+EXPORT void obs_frontend_set_swap_scenes_mode(bool enabled);
+
 EXPORT void obs_frontend_take_screenshot(void);
 EXPORT void obs_frontend_take_source_screenshot(obs_source_t *source);
 

frontend/api/obs-frontend-internal.hpp

@@ -102,6 +102,9 @@ struct obs_frontend_callbacks {
 	virtual obs_source_t *obs_frontend_get_current_preview_scene(void) = 0;
 	virtual void obs_frontend_set_current_preview_scene(obs_source_t *scene) = 0;
 
+	virtual bool obs_frontend_get_swap_scenes_mode(void) = 0;
+	virtual void obs_frontend_set_swap_scenes_mode(bool enabled) = 0;
+
 	virtual void on_load(obs_data_t *settings) = 0;
 	virtual void on_preload(obs_data_t *settings) = 0;
 	virtual void on_save(obs_data_t *settings) = 0;

frontend/widgets/OBSBasic.hpp

@@ -1583,10 +1583,13 @@ private slots:
 	void CurrentTransitionChanged(const QString &uuid);
 
 	void TransitionDurationChanged(const int &duration);
+	void SwapScenesModeChanged(bool enabled);
 
 public:
 	int GetTransitionDuration();
 	int GetTbarPosition();
+	bool GetSwapScenesMode() const { return swapScenesMode; }
+	void SetSwapScenesMode(bool enabled);
 
 	/* -------------------------------------
 	 * MARK: - OBSBasic_Updater

frontend/widgets/OBSBasic_StudioMode.cpp

@@ -126,7 +126,7 @@ void OBSBasic::CreateProgramOptions()
 		};
 
 		auto toggleSwapScenesMode = [this]() {
-			swapScenesMode = !swapScenesMode;
+			SetSwapScenesMode(!swapScenesMode);
 		};
 
 		auto toggleSceneDuplication = [this]() {

frontend/widgets/OBSBasic_Transitions.cpp

@@ -263,6 +263,22 @@ void OBSBasic::TransitionFullyStopped()
 		overridingTransition = false;
 	}
 }
+void OBSBasic::SetSwapScenesMode(bool enabled)
+
+{
+	QMetaObject::invokeMethod(this, [this, enabled]() {
+		if (swapScenesMode == enabled)
+			return;
+
+		swapScenesMode = enabled;
+
+		blog(LOG_INFO, "SwapScenesMode set to: %s", enabled ? "enabled" : "disabled");
+
+		emit SwapScenesModeChanged(enabled);
+
+		OnEvent(OBS_FRONTEND_EVENT_SWAP_SCENES_MODE_CHANGED);
+	});
+}
 
 void OBSBasic::TransitionToScene(OBSSource source, bool force, bool quickTransition, int quickDuration, bool black,
 				 bool manual)