So far the Unmanaged got released after an XCB_UNMAP_NOTIFY. This event
gets created after xcb_unmap_window or after xcb_destroy_window. In the
latter case the window is already distroyed and any of KWin's cleanup
calls will cause a BadWindow (or similar) error.
The idea to circumvent these errors is to try to wait for the
DESTROY_NOTIFY event. To do so the processing of the release is slightly
delayed. If KWin gets the destroy notify before the delay times out the
Unamanged gets released immediately but with a Destroy flag. For this a
new enum ReleaseToplevel is introduced and Unmanage::release takes this
as an argument instead of the bool which indicated OnShutdown. Also this
enum is added to Toplevel::finishCompositing so that it can ignore the
destroyed case and not generate an error.
REVIEW: 117422
93e5ebac63