This is a regression since Qt 6.3.2.

If I create main window initially (with a raster surface by default) and later QWebEngineView is added into any layout, the main window is hidden for a short period of time. This happens only once: if I create the first QWebEngineView. The main window is not hidden anymore if other instances of QWebEngineView are created.

After some investigation I found that it happens when a widget with OpenGL surface is reparented into a main window with a raster surface. In this case the surface type changes and resources of the main window are destroyed and recreated.

The sample code is attached: webengine-bug.cpp