Re: Bug in incremental undrawing of mouseover highlighting

[Stephen Berman]

GNU Emacs 22.0.91.2 (i686-pc-linux-gnu, GTK+ Version 2.8.10) of
2006-12-07 on escher

I experience this bug fairly often in relatively mild form which is
annoying but not unbearable.  But I've just run across a severe case
of presumably the same bug.  It occurred while reading
gnu-emacs-source from Gmane with Gnus.  The article that shows the
problem is at <http://permalink.gmane.org/gmane.emacs.sources/1977>,
and here's how to reproduce it:

1. emacs -Q
2. M-: (setq gnus-select-method '(nntp "news.gmane.org")) RET
3. M-x gnus RET
4. S s gmane.emacs.sources
5. RET
6. C-s M-e [ 187: Alf-Ivar Holm RET C-f RET, i.e., go to this article
and open it.
7. In the *Article* buffer, click on the MIME part header
[2. Displaying ISO week in calendar, updated for emacs 22, 2nd try ---
application/emacs-lisp; calendar-hack.el].  You'll see that the entire
text of the attachment has mouse-face highlighting, and if you scroll
over this part the incremental undrawing bug is apparent en masse.
Now click the MIME part header again to close it, and either the
entire header or the second line of will be double.  Further clicking
to open and close the MIME part increases the number of (parts of)
headers displayed.

Steve Berman