QWebEngineView: A blinking white dot displays on dark website

Simplified bug report

A blinking white dot appears on the window / widget when using OpenGL on Windows.

According to a few people it can be reproduced with multiple examples:

1. "Qt Quick Controls - Gallery" example: qt_source/qtquickcontrols2/examples/quickcontrols2/gallery/gallery.pro
2. https://bugreports.qt.io/secure/attachment/84270/84270_mcve_74492.cpp

3. import QtQuick 2.12
   import QtQuick.Window 2.12
   
   Window {    
     visible: true    
     width: 640    
     height: 480    
     color: 'black'   
    
     TextEdit {        
       anchors.centerIn: parent        
       width: 200        
       height: 20        
       text: 'Sample text'        
       color: 'red'    
     }
   }

Platform is Windows, details environment info is in Environment field.

Original bug report below

Note that this is independent of WebEngine and also happens with a variety of other Qt modules that use OpenGL (in contrast to OpenGL ES or software rendering).

For example open https://www.speedtest.net/fr for example you will see a blinking  white dot at the middle of the webview parasiting the display

This blinking dot shows up in many other website when the background is dark. 

The blinking dot shows up also on some youtube video.

Again you can see the blinking dot on the error when you open any metacafe video, (metacafe doesn't work with webengine it's another bug, but the intersting thing here is the white dot) 

Reportedly introduced by "Fix automatic showing/hiding of the Windows 10 on-screen keyboard" 3d867b8 https://codereview.qt-project.org/c/qt/qtbase/+/232927