GTK relies on the Glib event loop, which is in a separate library (and also used by Qt, at least optionally). You can, if you want to, reimplement the abstract

GTK relies on the Glib event loop, which is in a separate library (and also used by Qt, at least optionally). You can, if you want to, reimplement the abstract API of the Glib event loop, and use that with GTK instead. Note also that on macOS, GTK has to integrate both the Glib event loop and the event loop used by NeXTStep/Cocoa, because it is not always the case that the same one is in control (e.g. during drag-n-drop processing). It handles this "just fine", for some definition of "just fine".