2D: Fix rendering artefacts when using `BackBufferCopy`.

Fixes both GLES3 and RendererRD implementations

drivers/gles3/rasterizer_canvas_gles3.cpp

@@ -568,6 +568,8 @@ void RasterizerCanvasGLES3::canvas_render_items(RID p_to_render_target, Item *p_
 
 	// Clear out state used in 2D pass
 	reset_canvas();
+	state.current_batch_index = 0;
+	state.canvas_instance_batches.clear();
 	state.current_data_buffer_index = (state.current_data_buffer_index + 1) % state.canvas_instance_data_buffers.size();
 	state.current_instance_buffer_index = 0;
 }
@@ -662,8 +664,6 @@ void RasterizerCanvasGLES3::_render_items(RID p_to_render_target, int p_item_cou
 
 	if (index == 0) {
 		// Nothing to render, just return.
-		state.current_batch_index = 0;
-		state.canvas_instance_batches.clear();
 		return;
 	}
 
@@ -807,8 +807,6 @@ void RasterizerCanvasGLES3::_render_items(RID p_to_render_target, int p_item_cou
 	}
 
 	glDisable(GL_SCISSOR_TEST);
-	state.current_batch_index = 0;
-	state.canvas_instance_batches.clear();
 	state.last_item_index += index;
 }
 

servers/rendering/renderer_rd/renderer_canvas_render_rd.cpp

@@ -913,6 +913,9 @@ void RendererCanvasRenderRD::canvas_render_items(RID p_to_render_target, Item *p
 		RenderingServerDefault::redraw_request();
 	}
 
+	texture_info_map.clear();
+	state.current_batch_index = 0;
+	state.canvas_instance_batches.clear();
 	state.current_data_buffer_index = (state.current_data_buffer_index + 1) % BATCH_DATA_BUFFER_COUNT;
 	state.current_instance_buffer_index = 0;
 }
@@ -2286,9 +2289,6 @@ void RendererCanvasRenderRD::_render_batch_items(RenderTarget p_to_render_target
 
 	RD::get_singleton()->draw_list_end();
 
-	texture_info_map.clear();
-	state.current_batch_index = 0;
-	state.canvas_instance_batches.clear();
 	state.last_instance_index += instance_index;
 }
 
@@ -2975,7 +2975,7 @@ void RendererCanvasRenderRD::_canvas_texture_invalidation_callback(bool p_delete
 	KeyValue<RID, TightLocalVector<RID>> *kv = static_cast<KeyValue<RID, TightLocalVector<RID>> *>(p_userdata);
 	RD *rd = RD::get_singleton();
 	for (RID rid : kv->value) {
-		// the invalidation callback will take care of clearing rid_set_to_uniform_set cache also
+		// The invalidation callback will also take care of clearing rid_set_to_uniform_set cache.
 		rd->free(rid);
 	}
 	kv->value.clear();
@@ -3008,7 +3008,7 @@ void RendererCanvasRenderRD::_render_batch(RD::DrawListID p_draw_list, CanvasSha
 			uniform_set = &iter->data;
 			RD::get_singleton()->uniform_set_set_invalidation_callback(rid, RendererCanvasRenderRD::_uniform_set_invalidation_callback, (void *)&iter->key);
 
-			// If this is a CanvasTexture, it must be tracked so that any changes to the diffuse, normal
+			// If this is a CanvasTexture, it must be tracked so that any changes to the diffuse, normal,
 			// or specular channels invalidate all associated uniform sets.
 			if (ts->owns_canvas_texture(p_batch->tex_info->state.texture)) {
 				KeyValue<RID, TightLocalVector<RID>> *kv = nullptr;