bug#18285: 24.3.92; A combination of `display' on text and `invisible' and `before/after-string' leads to the before/after string being displayed twice

[Eli Zaretskii]

> Date: Sun, 24 Aug 2014 05:28:42 +0400
> From: Dmitry Gutov <dgutov@yandex.ru>
> CC: 18285@debbugs.gnu.org
> 
> On 08/23/2014 12:55 AM, Eli Zaretskii wrote:
> 
> > Look at the code inside load_overlay_strings that handles this, to
> > understand what I'm saying.
> 
> Do you mean the situation when the `invisible' overlay starts before the 
> `display' starts? And then we skip to the end because of `invisible', 
> but that position is covered by `display', so if we ignore the 
> `invisible' there, `before-string' would not be displayed?

No, I mean the situation where a before-string or after-string overlay
is put on invisible text.

> Basically, my suggestion was to ignore it when `display' already 
> performs all of its job. But the edge cases make it more complicated.

It's always the corner cases that add enormous complications.  We are
talking about such corner case.