When changing the window state from non-floating to floating (e.g. leaving fullscreen), libdecor can send bogus content sizes that are +/- the height of the window title bar and start 'walking' the window height in one direction or the other with every transition.
The floating window size is known, so use the cached value instead of the size reported by libdecor when restoring the floating state.
Frank Praznik
fe396e306e