bug#19307: 24.4.51; Ellipsis created with `invisible' removes highlighting from overlay after-string after it

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 03 Feb 2015 05:33:02 +0200
> From: Dmitry Gutov <dgutov@yandex.ru>
> CC: 19307@debbugs.gnu.org
> 
>     This bug was introduced in Emacs 23, 10 years(!) ago.
> 
> Don't know your feelings on this subject, but I'm kinda proud. :)

You should be.

> > Now fixed in
> 
>     commit 27e11c0 on the emacs-24 branch.
> 
> Thanks, but it introduced a regression. Insert some text at the end, and "xxx" will get displayed twice:

Turns out the bug I fixed concealed another one that was also there
for a long time (more than 9 years), and became exposed due to my fix.
Now fixed in commit e589765 on the emacs-24 branch.

> Not to diminish your efforts, but I've noticed that the fix for each display problem I've reported lately involved move added lines than removed ones. Which looks like adding more special cases. That's worrying.

The bugs happened in special cases for which no one coded the
solution, so catering to those cases often needs additional code.
Isn't that natural?

Say you have something like

  int reckless_division = a / b;

and then someone reports a divide-by-zero crash, and you add
protection against b being zero -- won't you expect the code to grow a
little?

Anyway, you should be happier with this last fix, since it removes
more lines than it adds ;-)