Re: Question about display engine

[Eli Zaretskii]

> 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.

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