> Thanks, this one reminds me of some previous patch in the respective
 > bug report: repeated set-frace-attribute are stable WRT the frame
 > size, but resizing the frame with the mouse and then evaling the
 > set-frame-attribute form resizes the frame (in the smaller direction).

That's the one where we then tried to make the frame larger by an entire
size increment minus the scaling residue.  Which means that here we
should make the frame larger by an entire size increment in the hope
that we size it back when we get notified.  Please try again.

martin