Image widget missing?
There doesn't seem to be a widget for displaying images. Useful if not necessary for things like image viewers and music players that show covers. GTK has a few different ways of doing it, it would probably be a good idea to support a couple of variants with different tradeoffs. A way to support async image loading would be very nice as well, maybe using GdkPixbuf: https://docs.gtk.org/gdk-pixbuf/type_func.Pixbuf.new_from_stream_async.html