Created attachment 171004 [details]
CMakeLists.txt

Hi all :-)

When you run a Plasma 6 desktop and run a program using a MarbleWidget, the widget shortly flashes up as an extra window after being instantiated. I'll attach a minimal example demonstrating this.

I saw this exact behavior with another project, always happening when QWidget::show() was called before the widget was added to a layout. This either did not happen using a Plasma 5 desktop, or at least the flashing was not visible.

For this exact case, I noticed it whilst using KGeoTag. On Plasma 5, everything is normal as usual. When I start KGeoTag on Plasma 6, the MarbleWidget flashes. Just like with the to-be-attached demo.

Maybe, you want to to fix this.

Cheers, Tobias