GNOME ignores the fontconfig rules

[maximilionus]

About

For some strange reason, GNOME DE completely ignores any fontconfig rule to set the font antialiasing method, meaning that it is completely impossible to make any custom value set with fontconfig to be respected by the environment.

While this is not a critical issue, as GNOME uses the grayscale antialiasing method by default, there are a few Linux distributions that change this setting to the subpixel mode, with Ubuntu being one of them.

"GNOME way"

GNOME DE has its own configuration methods, that are preferred over the freedesktop standards. These configurations can be easily accessed and modified through the gsettings utility. There are absolutely no other way to make changes to stuff like antialiasing method or hinting without the gsettings tool.

Temporary Solution

The solution to this issue for now is manual configuration on the user side, using the gsettings tool.

To see if your environment uses the subpixel font antialiasing you can check the output of the command below:

$ gsettings get org.gnome.desktop.interface font-antialiasing
'rgba'

If you get the same output as above - you are using the subpixel antialiasing, and switching to grayscale antialiasing can be done by executing the next command:

gsettings set org.gnome.desktop.interface font-antialiasing grayscale

To revert the changes:

gsettings reset org.gnome.desktop.interface font-antialiasing

[maximilionus]

Decided to make a few tests with KDE spin of Fedora just to make sure that this problem is GNOME-specific. Results: This problem is GNOME-specific. KDE Plasma respects all the fontconfig rules.

[maximilionus]

Started working on this problem and it's, uh... quite troublesome. Not only is the XDG_CURRENT_SESSION environment variable inaccessible on sudo run (without the -E flag), but the gsettings utility for GNOME configuration relies heavily on D-Bus, making it very hard to make any changes under sudo.

The next and main problem is automatic installation through the package manager. Here it becomes simply impossible to make such calls to the user environment.

So the only possible way to implement this would be a special profile.d script, which should check the environment only once after startup and make all the necessary gsettings calls.

[maximilionus]

Found this amazing feature, that allows to override the default GTK apps configuration, also works for GNOME "registry". It can be done by placing the file <NAME>.gschema.override in /usr/share/glib-2.0/schemas/:

[org.gnome.desktop.interface]
antialiasing='grayscale'

Note that this is not a fully functional example. In fact, I'm not even sure it works at all.

I am not entirely sure this will work out as intended, but it's definitely a much better way to handle these settings.

Example usage here.