bug#20984: 25.0.50; Combining accents don't display properly in certain fonts

[handa]

In article 
<CAAdUY-JQoRXbdHT3rERAVhfCb76cVViBD3i5y85dYR+sL5mqbA@mail.gmail.com>, Artur 
Malabarba <bruce.connor.am@gmail.com> writes:

> Indeed, this works.

Thank you for testing.  The next release of m17n-db will come with that
new version.

---
K. Handa
handa@gnu.org


> 2015-07-10 17:06 GMT+01:00 handa <handa@gnu.org>:
> > In article <83oajkbkbo.fsf@gnu.org>, Eli Zaretskii <eliz@gnu.org> writes:
> >
>>> Btw, I wonder why xftfont and libotf don't do the same as Uniscribe,
>>> i.e. instruct Emacs to display the à character.  This is what the
>>> composition data I see here says:
> >
>>> [0 1 97 231 8 1 7 12 4 nil]
> >
>>> This single vector tells Emacs to display one glyph, and 231 is its
>>> code in the font.
> >
>>> It is strange that libotf doesn't take this shortcut, although I'm
>>> quite sure a glyph for à is available both in DejaVu Sans Mono and in
>>> Source Code Pro.  But I don't know enough about libotf.
> >
> > Sorry, I found that my build of emacs-24.5 was without m17n-flt (and
> > libotf).  So, the combining was done by Emacs itself using the function
> > compose-gstring-for-graphic.
> >
> > I've just rebuild emacs-24.5 with m17n-flt, and see the same problem as
> > the trunk, which means that the culprit may be in m17n-flt or libotf.
> >
> > So, I checked m17n-flt and found that the rule for combining latin
> > characters has a bug when a font has such OTF features as subs, sups.
> >
> > Please try the attached COMBINING.flt by these steps:
> > 1. make the directory ~/.m17n.d
> > 2. put COMBINING.flt under that directory.
> > 3. run emacs
> >
> > By the why, the reason of m17n-flt/libotf not taking the shortcut above
> > is that the Source Code Pro font doesn't have such a feature.  I suspect
> > Uniscribe has a special code for using precomposed glyph without asking
> > a font about its features.  So, perhaps, even with TTF font (i.e. a font
> > of no OTF features), Uniscribe can display a-grave sequence with the
> > precomposed glyph.
> >
> > ---
> > K. Handa
> > handa@gnu.org
> >