Query default OS fonts

[jakoschiko]

Any ideas how to query the fonts that are configured as default in the OS? Is this in scope of this library?

In KDE the global fonts can be specified in the settings. I assume other platforms allow this, too.

[kepstin]

I think this is probably out of scope of this library, since finding the os fonts on linux requires interfacing with desktop-specific configuration interfaces. For example, on GNOME, you should first try using the XDG Settings Portal to fetch the org.gnome.desktop.interface.font-name key, then fallback to using gsettings. But you have to keep in mind that the value you get is a serialized Pango font description string - a different format from what fontconfig lookups use, so it has to be translated.

Although the full implementation of this feature is probably out of scope, it might make sense for rust-fontconfig to provide a convenient interface to set the preferred font family for the system-ui generic alias (and other CSS family name aliases, like ui-sans-serif, ui-monospace, etc.) at runtime.

[fschutt]

Although the full implementation of this feature is probably out of scope, it might make sense for rust-fontconfig to provide a convenient interface to set the preferred font family for the system-ui generic alias (and other CSS family name aliases, like ui-sans-serif, ui-monospace, etc.) at runtime.

Here is how I do it for now, feel free to copy.

[kepstin]

Here is how I do it for now, feel free to copy.

Details on the Pango FontDescription string format can be seen here, if you're interested in improving the method used for parsing the gsettings key: https://docs.gtk.org/Pango/type_func.FontDescription.from_string.html#description

Keep in mind that the method you're currently using, with the gsettings command line tool, will not return the correct value for apps running in a Flatpak environment, where the XDG Portal interface must be used instead.

[fschutt]

Eh thanks, I'll fix it "properly" once it actually becomes a problem in practice, right now I'm not on Linux so it's hard to test. My current goal is to just get some reftests running on Ubuntu to select the right font.

Right now (for 1.2.0) I just implemented some minimal hard-coded "common default fonts" for the strings sans-serif, serif, monospace, etc. - which vary based on OS and Unicode range. It's an intermediate solution.