fix: A better version of split_frame, releases immediately after frame rendering has ended.

Author: v-ein

dearpygui/_dearpygui.pyi

@@ -2271,19 +2271,26 @@ save_init_file(PyObject* self, PyObject* args, PyObject* kwargs)
 static PyObject*
 split_frame(PyObject* self, PyObject* args, PyObject* kwargs)
 {
-	i32 delay = 32;
-
-	if (!Parse((GetParsers())["split_frame"], args, kwargs, __FUNCTION__,
-		&delay))
+	if (!Parse((GetParsers())["split_frame"], args, kwargs, __FUNCTION__))
 		return GetPyNone();
 
-	// std::lock_guard<std::recursive_mutex> lk(GContext->mutex);
+	if (GContext->running)
+	{
+		Py_BEGIN_ALLOW_THREADS;
+		std::unique_lock lk(GContext->frameEndedMutex);
+		GContext->frameEnded = false;
+		GContext->frameEndedEvent.wait(lk, []{return GContext->frameEnded;});
+		lk.unlock();
 
-	Py_BEGIN_ALLOW_THREADS;
-	GContext->waitOneFrame = true;
-	while (GContext->waitOneFrame)
-		std::this_thread::sleep_for(std::chrono::milliseconds(delay));
-	Py_END_ALLOW_THREADS;
+		Py_END_ALLOW_THREADS;
+	}
+
+	// Now let's see if it was successful (there's a chance that DPG got stopped while we were waiting)
+	if (!GContext->running)
+	{
+		mvThrowPythonError(mvErrorCode::mvNone, "split_frame is exiting: there is no active rendering loop.");
+		return nullptr;
+	}
 
 	return GetPyNone();
 }
@@ -2654,7 +2661,7 @@ destroy_context(PyObject* self, PyObject* args, PyObject* kwargs)
 	else
 	{
 		// Make sure everyone knows we're shutting down, even if stop_dearpygui
-		// was not called.
+		// was not called.  This also releases any waiting split_frame calls.
 		StopRendering();
 
 		Py_BEGIN_ALLOW_THREADS;

dearpygui/_dearpygui_RTD.py

@@ -564,7 +564,7 @@ InsertParser_Block1(std::map<std::string, mvPythonParser>& parsers)
 
 	{
 		std::vector<mvPythonDataElement> args;
-		args.push_back({ mvPyDataType::Integer, "delay", mvArgType::KEYWORD_ARG, "32", "Minimal delay in in milliseconds" });
+		args.push_back({ mvPyDataType::Integer, "delay", mvArgType::DEPRECATED_REMOVE_KEYWORD_ARG, "32", "Do not use it anymore, it has no effect." });
 
 		mvPythonParserSetup setup;
 		setup.about = "Waits one frame.";

dearpygui/dearpygui.py

@@ -182,20 +182,22 @@ Render()
 
     mvToolManager::Draw();
 
+    if (GContext->resetTheme)
     {
-        if (GContext->resetTheme)
-        {
-            SetDefaultTheme();
-            GContext->resetTheme = false;
-        }
-
-        mvRunTasks();
-        RenderItemRegistry(*GContext->itemRegistry);
-        mvRunTasks();
+        SetDefaultTheme();
+        GContext->resetTheme = false;
     }
 
-    if (GContext->waitOneFrame == true)
-        GContext->waitOneFrame = false;
+    mvRunTasks();
+    RenderItemRegistry(*GContext->itemRegistry);
+    mvRunTasks();
+
+    // release split_frame if it's waiting for the frame end
+    {
+        std::lock_guard lk(GContext->frameEndedMutex);
+        GContext->frameEnded = true;
+    }
+    GContext->frameEndedEvent.notify_all();
 }
 
 std::map<std::string, mvPythonParser>& 
@@ -206,7 +208,20 @@ GetParsers()
 
 void StopRendering()
 {
+    // While it may seem reasonable to set it to false with frameEndedMutex locked
+    // (to set it simultaneously with frameEnded), we don't want to spur another
+    // race condition between split_frame() and is_dearpygui_running() in the
+    // rendering loop.  Let's trigger it as early as possible.
     GContext->running = false;
+
+    // Unblock handlers (or other code) that might be waiting in `split_frame()`
+    {
+        std::lock_guard lk(GContext->frameEndedMutex);
+        // Simulate an end of frame even though there's no real frame this time.
+        // Otherwise split_frame will continue waiting.
+        GContext->frameEnded = true;
+    }
+    GContext->frameEndedEvent.notify_all();
 }
 
 void 

src/dearpygui_commands.h

@@ -102,7 +102,9 @@ struct mvIO
 
 struct mvContext
 {
-    std::atomic_bool    waitOneFrame       = false;
+    std::mutex          frameEndedMutex;
+    std::condition_variable frameEndedEvent;
+    bool                frameEnded         = false;
     // Indicates whether DPG has started at least once in this context, i.e. whether
     // associated Dear ImGui contexts exist and can be read from.
     std::atomic_bool    started            = false;