This past week Cairo gutted out its old back-ends for Qt (limited to Qt4), Cogl that is no longer maintained , OpenVG, BeOS as it doesn't support the Meson build system, OS/2 as it also doesn't support Meson and might not be in a working state since 2006 (last tested), DirectFB as it's been dead (though DirectFB2 was recently started ), and the DRM back-end that was an experiment and broken now for at least a decade.
Emmanuele Bassi commented with the removal , " This is a lot of code that exists only as a trap for unwary travelers, or a maintenance sink. Removing the Qt and BeOS backends alone allows us to drop the dependency on a C++ compiler in our build systems, as well as removing the complexity of dealing with one. "
There have also been other improvements merged to Cairo this past week besides the removing of decade old code rot.