Re: Question about display engine

[Ergus]

On Sun, Oct 13, 2019 at 09:53:13PM +0300, Eli Zaretskii wrote:
> > Date: Sun, 13 Oct 2019 20:25:42 +0200
> > From: Ergus <address@hidden>
> > Cc: address@hidden, address@hidden
> >
> > >Then looking at the position that causes the error will probably tell
> > >you what's wrong.  (Is OBJECT passed to Fget_text_property a string?
> > >if not, position of zero is invalid.)
> > >
> >
> > Actually conditioning the call to face_at_pos to when IT_CHARPOS (*it)
> > != 0 seems to fix the issue with magit... but maybe we are just hiding
> > something under the carpet here. Can you imagine something more general
> > than that just this condition?
>
> How did it happen that IT_CHARPOS(*it) is zero?  If we are iterating
> over a buffer, that cannot happen, because we begin from 1 and go
> forward.
If you see the bt I sent before the problem is in display_mode_line.

> Is it->sp zero or higher?  If it's higher, then we are not iterating
> over a buffer, but something else (a string, an image, or something
> similar).  What are the values of it->method and it->what?  Can you
> show the result of
>
>  (gdb) pgrowx it->glyph_row