Current problems: * other widgets in a GL-painted window are low-resolution on Retina display * something wrong with paint updates; gdkgears demo only updates every couple of seconds but reports ~30fps See: #517
This makes sure the Quartz backend returns an error when asked to create a GL context, rather than crashing because of a NULL vfunc. https://bugzilla.gnome.org/show_bug.cgi?id=740199