Remove old backends
We are still stringing along a few backends that have been broken for a decade; or depend on libraries that have been unmaintained and unsupported for almost as long:
- Qt: depends on Qt 4, EOL in 2015
- Cogl: depends on Cogl, unmaintained since 2016
- OpenVG
- BeOS: unsupported by Meson
- OS/2: unsupported by Meson, last known built for Cairo 1.12 (2006)
- DirectFB
- DRM: science experiment, broken for at least 10 years
This is a lot of code that exists only as a trap for unwary travellers, 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.
Edited by Emmanuele Bassi