Re: Cairo font selection for Ethiopic

[mituharu@math.s.chiba-u.ac.jp]

> On Fri, 21 Jun 2019 10:54:03 +0900 YAMAMOTO Mitsuharu
> <mituharu@math.s.chiba-u.ac.jp> wrote:
>
>> On Fri, 21 Jun 2019 04:30:09 +0900,
>> Stephen Berman wrote:
>>>
>>> I don't know if this is a bug or just the way Cairo works.  On two
>>> different GNU/Linux systems I have built Emacs both --with-cairo and
>>> without.  The non-Cairo builds use Xft as the font backend.  On those
>>> builds the Ethiopic scripts (Amharic and Tigrinya) in HELLO are
>>> displayed with the Goha-Tibeb Zemen font.  In the Cairo builds this
>>> font
>>> is not used for these scripts; instead, on one system they are
>>> displayed
>>> with a mix of GNU Unifont and mutt-clearlyu, and on the other system,
>>> which lacks these fonts, only hex boxes are displayed.  Is there
>>> something about Goha-Tibeb Zemen that is incompatible with Cairo?
>>
>> Goha-Tibeb Zemen does not have glyphs for ASCII printables that the
>> ftcr font backend relies on computing minimum/average/space width when
>> opening the font.  The patch below should simulate the Xft behavior.
>
> Thanks.  I rebuilt Emacs --with-cairo with this patch but the Ethiopic
> scripts in HELLO are still not displayed with Goha-Tibeb Zemen but also
> not with the same fonts as before: now they are uniformly displayed with
>
> -Misc-Misc Fixed Wide-normal-normal-normal-ja-13-*-*-*-c-120-iso10646-1
>
> Is this the intended result of the patch?

The patch enables us to use the Goha-Tibeb Zemen font on cairo
build.  If you manually specify the font for Ethiopic characters,
then they should be displayed with the font.

(let ((script 'ethiopic)
      (coverage))
  (map-char-table
   #'(lambda (range val)
       (when (eq val script)
	 (if (consp range)
	     (setq range (cons (car range) (cdr range))))
	 (push range coverage)))
   char-script-table)
  (dolist (range coverage)
    (set-fontset-font t range (font-spec :family "Goha-Tibeb Zemen"))))

Whether it is selected automatically in the default setting is
another problem and depends on several factors.  What are the
outputs of the ldd command for both non-cairo and cairo builds?

					YAMAMOTO Mitsuharu
				mituharu@math.s.chiba-u.ac.jp