`gtk_widget_set_app_paintable` is gone in GTK4 with no obvious replacement
gtk_widget_set_app_paintable seems to have disappeared in GTK4 without a deprecation warning or mention in the migration guide.
My goal is to have a transparent window with as child a vbox congaing a drawing area, but the background drawing prevents transparent backgrounds. In GTK3 this was widely known as possible after setting app_paintable to true, but in GTK4 this isn't possible anymore so transparent windows as a whole seem to be mostly impossible.
It is still possible to set the opacity on the window, but this changes the opacity of the whole window including child widgets making it useless for this purpose.
I would like to have it at least mentioned in the migration guide that its gone, if possible with an alternative to use for this purpose.