bug#44784: Combining accent is not combining

[Eli Zaretskii <eliz@gnu.org>]

> From: Juri Linkov <juri@linkov.net>
> Cc: 44784@debbugs.gnu.org
> Date: Sat, 21 Nov 2020 22:35:11 +0200
> 
> > Btw, the report by Emacs 27's "C-u C-x =", viz.:
> >
> >   Composed with the following character(s) "́" using this font:
> >     xfthb:-PfEd-DejaVu Sans Mono-normal-normal-normal-*-22-*-*-*-m-0-iso10646-1
> >   by these glyphs:
> >     [0 1 1071 878 13 0 13 16 0 nil]
> >     [0 1 769 649 13 4 11 17 -13 [0 0 0]]
> >
> > explicitly says that character composition _did_ happen here, it's
> > just the display that is broken.  And I guess that moving point to
> > these characters will show a "fat" cursor that includes both the base
> > character and the accent, once again showing that Emacs did compose
> > the accent with the preceding character.
> 
> Actually, separate cursor is shown on a character and separate on its
> combining character, so it seems they are not composed.

The 2 vectors you show above, let alone the "composed with" part,
explicitly say they _were_ composed.  So something else is going on
here.