Sorry opening this topic again, but the current behavior isn't really satisfying. I have a plugin with lots of different kinds of popups and sub-windows. The easiest way to rescale them is just to use setGobalScaleFactor, but this will also rescale the main-window-content which will not work properly on all different hosts/formats.
So either setGlobalScaleFactor should have no impact main-window-component (and doing it by myself, rescaling a subcomponent)
or there should be some wrapper implicit logic, that the plugin-window will be resized to fit its content (which i would prefer)