added option to disable automatic clearing of viewport render buffer

3 files changed, 40 insertions, 2 deletions

diff --git a/servers/visual/visual_server_raster.cpp b/servers/visual/visual_server_raster.cpp
index cef6fe567d..4c12ac9670 100644
--- a/servers/visual/visual_server_raster.cpp
+++ b/servers/visual/visual_server_raster.cpp
@@ -1576,6 +1576,15 @@ void VisualServerRaster::viewport_set_render_target_vflip(RID p_viewport,bool p_
 
 }
 
+void VisualServerRaster::viewport_set_render_target_clear_on_new_frame(RID p_viewport,bool p_enable) {
+
+	Viewport *viewport = viewport_owner.get( p_viewport );
+	ERR_FAIL_COND(!viewport);
+
+	viewport->render_target_clear_on_new_frame=p_enable;
+
+}
+
 void VisualServerRaster::viewport_set_render_target_to_screen_rect(RID p_viewport,const Rect2& p_rect) {
 
 	Viewport *viewport = viewport_owner.get( p_viewport );
@@ -1594,6 +1603,23 @@ bool VisualServerRaster::viewport_get_render_target_vflip(RID p_viewport) const{
 
 }
 
+bool VisualServerRaster::viewport_get_render_target_clear_on_new_frame(RID p_viewport) const{
+
+	const Viewport *viewport = viewport_owner.get( p_viewport );
+	ERR_FAIL_COND_V(!viewport,false);
+
+	return viewport->render_target_clear_on_new_frame;
+
+}
+
+void VisualServerRaster::viewport_render_target_clear(RID p_viewport) {
+
+	Viewport *viewport = viewport_owner.get( p_viewport );
+	ERR_FAIL_COND(!viewport);
+
+	viewport->render_target_clear=true;
+
+}
 
 void VisualServerRaster::viewport_queue_screen_capture(RID p_viewport) {
 
@@ -6605,7 +6631,10 @@ void VisualServerRaster::_draw_viewport(Viewport *p_viewport,int p_ofs_x, int p_
 	} else if (true /*|| !p_viewport->canvas_list.empty()*/){
 
 		//clear the viewport black because of no camera? i seriously should..
-		rasterizer->clear_viewport(clear_color);
+		if (p_viewport->render_target_clear_on_new_frame || p_viewport->render_target_clear) {
+			rasterizer->clear_viewport(clear_color);
+			p_viewport->render_target_clear=false;
+		}
 	}
 
 	if (!p_viewport->hide_canvas) {
diff --git a/servers/visual/visual_server_raster.h b/servers/visual/visual_server_raster.h
index eec677068e..78a4e77170 100644
--- a/servers/visual/visual_server_raster.h
+++ b/servers/visual/visual_server_raster.h
@@ -468,6 +468,8 @@ class VisualServerRaster : public VisualServer {
 		bool transparent_bg;
 		bool queue_capture;
 		bool render_target_vflip;
+		bool render_target_clear_on_new_frame;
+		bool render_target_clear;
 		Image capture;
 
 		bool rendered_in_prev_frame;
@@ -494,7 +496,7 @@ class VisualServerRaster : public VisualServer {
 
 		SelfList<Viewport> update_list;
 
-		Viewport() : update_list(this) { transparent_bg=false; render_target_update_mode=RENDER_TARGET_UPDATE_WHEN_VISIBLE; queue_capture=false; rendered_in_prev_frame=false; render_target_vflip=false;}
+		Viewport() : update_list(this) { transparent_bg=false; render_target_update_mode=RENDER_TARGET_UPDATE_WHEN_VISIBLE; queue_capture=false; rendered_in_prev_frame=false; render_target_vflip=false; render_target_clear_on_new_frame=true; render_target_clear=true;}
 	};
 
 	SelfList<Viewport>::List viewport_update_list;
@@ -957,6 +959,9 @@ public:
 	virtual RID viewport_get_render_target_texture(RID p_viewport) const;
 	virtual void viewport_set_render_target_vflip(RID p_viewport,bool p_enable);
 	virtual bool viewport_get_render_target_vflip(RID p_viewport) const;
+	virtual void viewport_set_render_target_clear_on_new_frame(RID p_viewport,bool p_enable);
+	virtual bool viewport_get_render_target_clear_on_new_frame(RID p_viewport) const;
+	virtual void viewport_render_target_clear(RID p_viewport);
 	virtual void viewport_set_render_target_to_screen_rect(RID p_viewport,const Rect2& p_rect);
 
 	virtual void viewport_queue_screen_capture(RID p_viewport);
diff --git a/servers/visual/visual_server_wrap_mt.h b/servers/visual/visual_server_wrap_mt.h
index c94425c586..cb69f79cbc 100644
--- a/servers/visual/visual_server_wrap_mt.h
+++ b/servers/visual/visual_server_wrap_mt.h
@@ -967,6 +967,10 @@ public:
 	FUNC2(viewport_set_render_target_vflip,RID,bool);
 	FUNC1RC(bool,viewport_get_render_target_vflip,RID);
 	FUNC2(viewport_set_render_target_to_screen_rect,RID,const Rect2&);
+	
+	FUNC2(viewport_set_render_target_clear_on_new_frame,RID,bool);
+	FUNC1RC(bool,viewport_get_render_target_clear_on_new_frame,RID);
+	FUNC1(viewport_render_target_clear,RID);
 
 	FUNC1(viewport_queue_screen_capture,RID);
 	FUNC1RC(Image,viewport_get_screen_capture,RID);