Add ability to specify a transition when calling TransitionToProgram

PROTOCOL.md

@@ -377,8 +377,14 @@ __Response__ : OK if specified scene exists, error otherwise.
 #### "TransitionToProgram"
 Studio Mode only. Transitions the currently previewed scene to Program (main output).
 
-__Request fields__ : none  
-__Response__ : always OK. No additional fields.
+__Request fields__ :  
+- **"with-transition" (object, optional) : if specified, use this transition when switching from preview to program. This will change the current transition in the frontend to this one.
+
+__Response__ : always OK. No additional fields
+
+An object passed as `"with-transition"` in a request must have the following fields :  
+- **"name"** (string) : transition name
+- **"duration"** (integer, optional) : transition duration in milliseconds
 
 ---
 

Utils.cpp

@@ -241,6 +241,23 @@ void Utils::SetTransitionDuration(int ms)
 	}
 }
 
+bool Utils::SetTransitionByName(const char* transition_name)
+{
+	obs_source_t *transition = GetTransitionFromName(transition_name);
+
+	if (transition)
+	{
+		obs_frontend_set_current_transition(transition);
+		obs_source_release(transition);
+
+		return true;
+	}
+	else
+	{
+		return false;
+	}
+}
+
 QPushButton* Utils::GetPreviewModeButtonControl()
 {
 	QMainWindow* main = (QMainWindow*)obs_frontend_get_main_window();

Utils.h

@@ -45,6 +45,8 @@ class Utils
 		static int GetTransitionDuration();
 		static void SetTransitionDuration(int ms);
 
+		static bool SetTransitionByName(const char* transition_name);
+
 		static QPushButton* GetPreviewModeButtonControl();
 		static QLayout* GetPreviewLayout();
 		static QListWidget* GetSceneListControl();

WSRequestHandler.cpp

@@ -437,20 +437,14 @@ void WSRequestHandler::HandleGetCurrentTransition(WSRequestHandler *owner)
 void WSRequestHandler::HandleSetCurrentTransition(WSRequestHandler *owner)
 {
 	const char *name = obs_data_get_string(owner->_requestData, "transition-name");
-	obs_source_t *transition = Utils::GetTransitionFromName(name);
 
-	if (transition)
-	{
-		obs_frontend_set_current_transition(transition);
+	bool success = Utils::SetTransitionByName(name);
+
+	if (success)
 		owner->SendOKResponse();
-
-		obs_source_release(transition);
-	}
 	else
-	{
 		owner->SendErrorResponse("requested transition does not exist");
 }
-}
 
 void WSRequestHandler::HandleSetTransitionDuration(WSRequestHandler *owner)
 {
@@ -808,6 +802,30 @@ void WSRequestHandler::HandleSetPreviewScene(WSRequestHandler *owner)
 
 void WSRequestHandler::HandleTransitionToProgram(WSRequestHandler *owner)
 {
+	obs_data_t* transitionInfo = obs_data_get_obj(owner->_requestData, "with-transition");
+
+	if (transitionInfo)
+	{
+		const char* transitionName = obs_data_get_string(transitionInfo, "name");
+		int transitionDuration = obs_data_get_int(transitionInfo, "duration");
+
+		if (!transitionName)
+		{
+			owner->SendErrorResponse("specified transition doesn't exist");
+			return;
+		}
+
+		bool success = Utils::SetTransitionByName(transitionName);
+		if (!success)
+		{
+			owner->SendErrorResponse("unknown error while trying to change current transition");
+			return;
+		}
+
+		if (transitionDuration > 0)
+			Utils::SetTransitionDuration(transitionDuration);
+	}
+
 	Utils::TransitionToProgram();
 	owner->SendOKResponse();
 }