restoreGeometry() fails on multiscreen setup when application is maximized on Linux.

Observed on various linux flavors (RedHat, OpenSuse), both with Gnome or KDE desktops.

Compile and run the attached example. Make sure the application is maximized.

From the menu do a "Clear saved geometry" to make sure nothing is stored in the settings, then a "Save geometry" followed by a "Restore saved geometry.

Attached images show the results before and after restore: after restoring the geometry the window is maximized, but the widgets inside are restored to the non-maximized geometry only.