@Jacob.zhang That works, so visiblity do the trick. Thanks.

Hi
Does the custom CustomQWidget do its own drawing with QPainter ?

Also, if you are on Qt 5.4 or newer, I suggest replacing QGLWidget with QOpenGLWidget. QOpenGLWidget resolves numerous issues with QGLWidget: https://blog.qt.io/blog/2014/09/10/qt-weekly-19-qopenglwidget/

I was always searching at the wrong place.

The blue hue wasn't a problem of the style, it was a problem of the icon. Here is the solution:

for all icons

m_clientIcon.normal.addFile("plugins\\qtTsOverlay\\client.png");

add this

m_clientIcon.normal.addFile("plugins\\qtTsOverlay\\client.png", QSize(), QIcon::Selected);

Thank you very much for your help. I'm going to find another way to avoid this "borderline" situation. Anyway I think it will be a nice to have feature!

@jimmy274 You're Welcome :)
A more interesting way but through C++ would be to use QQuickPaintedItem to create your own custom item. You can re-implement paint method to draw your custom shapes, text etc.. It uses QPainter to achieve this. Try looking for setCompositionMode and setClipRegion methods. An example for QQuickPaintedItem is here.