improve quick panel switch state

src/node_stroke_preview.cpp

@@ -545,7 +545,8 @@ void NodeStrokePreview::draw_stroke()
                     gl.restore();
                     node->app_redraw();
                     node->async_end();
-                    std::this_thread::sleep_for(std::chrono::milliseconds(30));
+                    //std::this_thread::sleep_for(std::chrono::milliseconds(30));
+                    std::this_thread::yield();
                 }
             }
             App::I.async_start();