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@gnu.org> wrote:

> From: Mike <mikeandmore@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.