bug#63271: 29.0.90; broken mouse-face

[Gregory Heytings]

> > I finished bisection, and not sure if this helps, but that commit was 
> > 85a078e7853.
>
> Thanks, but I don't see how this could be true: those changes are all 
> conditioned by HAIKU-related conditionals, and I don't suppose you run a 
> Haiku build of Emacs, right?

Git bisect is always right.  I confirm that this bug is due to 85a078e785, 
which added, in ftcrfont_draw, a

s->background_filled_p = 1;

statement inside a #ifndef USE_BE_CAIRO (note the "n").  A few days later 
a1aa9cbf57 moved that statement ouside of the conditional.  Removing that 
statement fixes the bug.  I'm not sure what that statement is supposed to 
do however, it might be necessary, but only for Haiku.