GNU bug report logs - #79090
Respects Fontconfig settings for ftcr and ftcrhb font backends

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From: Mike <mikeandmore <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: Po Lu <luangruo <at> yahoo.com>, 79090 <at> debbugs.gnu.org
Subject: bug#79090: Respects Fontconfig settings for ftcr and ftcrhb font backends
Date: Wed, 30 Jul 2025 19:30:17 -0400

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Hi

Here's how I tested this.

1. I have the following base settings in fontconfig. They disable hinting
and autohint, so that Freetype will preserve the font shapes when rendering
web fonts.

  <match target="pattern">
    <edit name="antialias" mode="assign"><bool>true</bool></edit>
    <edit name="globaladvance" mode="assign"><bool>true</bool></edit>
    <edit name="embeddedbitmap" mode="assign"><bool>false</bool></edit>
    <edit name="hinting" mode="assign"><bool>false</bool></edit>
    <edit name="hintstyle" mode="assign"><const>hintnone</const></edit>
    <edit name="rgba" mode="assign"><const>rgb</const></edit>
    <edit name="autohint" mode="assign"><bool>false</bool></edit>
    <edit name="lcdfilter" mode="assign"><const>lcddefault</const></edit>
  </match>

2. Enable hinting for specific local fonts so that I can use them inside
Emacs with a smaller font size.

  <match target="font">
    <test name="family"><string>Hack</string></test>
    <edit name="hinting" mode="assign"><bool>true</bool></edit>
    <edit name="hintstyle" mode="assign"><const>hintfull</const></edit>
  </match>

For this step, you can also enable hinting in font-spec under Emacs.

Here are the screenshots. They are taken on a HiDPI display, and I'm going
to retake them tomorrow at work where we have low DPI displays.

Thanks
Mike


On Fri, Jul 25, 2025 at 3:34 AM Eli Zaretskii <eliz <at> gnu.org> wrote:

> > From: Mike <mikeandmore <at> gmail.com>
> > Date: Thu, 24 Jul 2025 21:12:36 -0400
> >
> > The ftcr and ftcrhb backends use cairo to render fonts, but cairo does
> > not respect font specific fontconfig settings. This patch queries
> > fontconfig with the specific font, and then it translates the fontconfig
> > settings into cairo font settings.
> >
> > Both backends would also ignore :hinting and :autohint properties from
> > the font-spec. This patch fixes that too.
>
> Thanks.
>
> I don't use Fontconfig and Cairo, so someone else who does will need
> to review the patch and try it.  Would you please post a procedure to
> test this patch once applied?
>
> Also, I wonder if this will have any user-level effects, and if so,
> should we have a NEWS entry about that?
>
> And finally, to accept changes of this size, we will need you to sign
> a copyright-assignment agreement with FSF.  If you are willing to do
> that, I will send you the form to fill and the instructions to go with
> it.
>


-- 
Thanks
Mike

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