Re: Pango-like font fallback (was Re: Russian numero sign)

[Kenichi Handa <handa@m17n.org>]

Paul Pogonyshev <pogonyshev@gmx.net> writes:

>> Please note that Pango and the other modern rendering
>> engines use TrueType font with a help of freetype/Xft and
>> fontconfig libraries.  Emacs (and emacs-unicode-2 too)
>> currently doesn't use them, but there exists an ongoing
>> project for supporting TTF in Emacs.

> That is a valid reason why Emacs cannot use Pango (yet), but it
> doesn't mean Emacs cannot implement similar substitution heuristic
> without Pango and for a different font class.  As I understand, you
> did that in the `emacs-unicode-2' branch.  It is not something simple,
> but Emacs is not simple to begin with.

I drastically changed the internal structure of fontset in
emacs-unicode-2.  We can't do such a change for the HEAD
(which will be the next release, I hope, soon).

>> First of all, do you have any iso10646-1 X core fonts that
>> support Cyrillic characters?

> No idea, sorry.  How do I check?  As I wrote above, Emacs does
> display Cyrillic characters (newly typed) when `unify-8859-on-decoding'
> is off.  And already existing characters are displayed no matter if
> that mode is active or not.

% xlsfonts -fn -*-*-medium-r-normal-*-*-*-*-*-*-*-iso10646-1

gives you a list of iso10646-1 X core fonts usable from
Emacs.  For instance, if this font is found...
-misc-fixed-medium-r-normal--14-130-75-75-c-70-iso10646-1

% xfd -fn -misc-fixed-medium-r-normal--14-130-75-75-c-70-iso10646-1

shows you the supported glyphs.  Please check the block
0x000400.  If you see cyrillic glyphs there, that font is
what you need.  You can do this to use that font.

(set-fontset-font
 "fontset-default"
 'mule-unicode-0100-24ff
 '("FOUNDRY-FAMILY" . "iso10646-1"))

Here FOUNDRY-FAMILY is misc-fixed in the above case.

If you surely don't have a proper iso10646-1 font, the next
method you can try is to customize utf-fragment-on-decoding
to t.  Even with the default setting of
unify-8859-on-decoding/off and unify-8859-on-encoding/on, if
utf-fragment-on-decoding is on, when you read an utf-8
cyrillic file, characters and decoded into
cyrillic-iso8859-5 charsets, thus you should see glyphs with
your iso8859-5 fonts.

---
Kenichi Handa
handa@m17n.org