Re: Bug in incremental undrawing of mouseover highlighting

[Chong Yidong <cyd@stupidchicken.com>]

>> Also, I think this is a bad timing to commit such a change for a
>> non-critical bug without approval by some expert.

If anyone has a suggestion for a cleaner non-invasive change, it would
be welcome.  I'm also agreeable to postphoning this bugfix till after
the release, if it is considered unsafe.

> I don't consider myself much of a redisplay expert, but I did express
> a (different) concern for the patch as posted, a concern that
> seemingly had no effect whatsoever.

It's still unclear, from the messages you sent, whether this bug can
happen outside of HAVE_WINDOW_SYSTEM.  The bugfix is meant to plug a
loophole in the code in note_mouse_highlight that computes whether or
not the mouse highlight has been updated, which is only present for
HAVE_WINDOW_SYSTEM.  (It is possible to change note_mouse_highlight
itself, e.g. by introducing dpyinfo->mouse_face_buffer.  This turns
out, however, to be a fairly intricate change.)