bug#18417: 24.3.93; posn-at-point confused by fill-column-indicator

[Eli Zaretskii]

> Date: Sun, 7 Sep 2014 15:52:34 -0400
> From: Alp Aker <alptekin.aker@gmail.com>
> Cc: Dmitry Gutov <dgutov@yandex.ru>, 18417@debbugs.gnu.org
> 
> > There are 2 special characters, u+e000 and u+e001, each one has a
> > display-table setting to display it as something else, then there's an
> > empty overlay with an after-string made of these special characters
> > that has a display property with :align-to, followed by an image...
> > And I'm not sure I listed all of the "features". (The 'cursor'
> > property I omitted intentionally, because I believe I know why they
> > are needed.) Why each one of these is needed?
> 
> At least some of that is cruft, as at one point I was trying to support all of
> v22, v23, and v24, and there were various differences in the behavior of
> overlay-strings (as well as the 'cursor property) among those versions.

That was my guess, yes.

> I'll try to simplify the implementation and see if I can come up
> with something that doesn't trigger any UB in the display engine.

Thank you.