Fix drawing of viewports without swapping buffers

servers/rendering/renderer_rd/renderer_compositor_rd.cpp

@@ -103,8 +103,9 @@ void RendererCompositorRD::begin_frame(double frame_step) {
 }
 
 void RendererCompositorRD::end_frame(bool p_swap_buffers) {
-	// TODO: Likely pass a bool to swap buffers to avoid display?
-	RD::get_singleton()->swap_buffers();
+	if (p_swap_buffers) {
+		RD::get_singleton()->swap_buffers();
+	}
 }
 
 void RendererCompositorRD::initialize() {

servers/rendering/renderer_viewport.cpp

@@ -616,7 +616,7 @@ void RendererViewport::_draw_viewport(Viewport *p_viewport) {
 	}
 }
 
-void RendererViewport::draw_viewports() {
+void RendererViewport::draw_viewports(bool p_swap_buffers) {
 	timestamp_vp_map.clear();
 
 	// get our xr interface in case we need it
@@ -799,11 +799,14 @@ void RendererViewport::draw_viewports() {
 	total_draw_calls_used = draw_calls_used;
 
 	RENDER_TIMESTAMP("< Render Viewports");
-	//this needs to be called to make screen swapping more efficient
-	RSG::rasterizer->prepare_for_blitting_render_targets();
 
-	for (const KeyValue<int, Vector<BlitToScreen>> &E : blit_to_screen_list) {
-		RSG::rasterizer->blit_render_targets_to_screen(E.key, E.value.ptr(), E.value.size());
+	if (p_swap_buffers) {
+		//this needs to be called to make screen swapping more efficient
+		RSG::rasterizer->prepare_for_blitting_render_targets();
+
+		for (const KeyValue<int, Vector<BlitToScreen>> &E : blit_to_screen_list) {
+			RSG::rasterizer->blit_render_targets_to_screen(E.key, E.value.ptr(), E.value.size());
+		}
 	}
 }
 

servers/rendering/renderer_viewport.h

@@ -299,7 +299,7 @@ public:
 	void handle_timestamp(String p_timestamp, uint64_t p_cpu_time, uint64_t p_gpu_time);
 
 	void set_default_clear_color(const Color &p_color);
-	void draw_viewports();
+	void draw_viewports(bool p_swap_buffers);
 
 	bool free(RID p_rid);
 

servers/rendering/rendering_server_default.cpp

@@ -88,7 +88,7 @@ void RenderingServerDefault::_draw(bool p_swap_buffers, double frame_step) {
 
 	RSG::scene->render_probes();
 
-	RSG::viewport->draw_viewports();
+	RSG::viewport->draw_viewports(p_swap_buffers);
 	RSG::canvas_render->update();
 
 	if (OS::get_singleton()->get_current_rendering_driver_name() != "opengl3" && OS::get_singleton()->get_current_rendering_driver_name() != "opengl3_angle") {