> I've rewritten the mouse code completely, patch attached.  It neither
 > fixes the GTK child frame resizing problem nor the jumping issues in
 > Lucid but should provide better dragging of frames via internal borders
 > and mode-/header-line otherwise.  In particular the drift you mentioned
 > above should be gone now.  Please try it.

The new patch attached now uses different API functions for resizing +
moving frames.  The function is called 'x-set-frame-size-and-position'
and works only under X and GTK.  It makes mouse-dragging X frames about
as smooth as the old GTK code did here (tested with Lucid, Motif and
without toolkit support).  I doubt that it also solves the GTK child
frame resize issue but you could nevertheless give it a try.

martin