gobject:type-is-a (gtype is-a-type)

gtype -- a g:type-t type ID to check anchestry for
is-a-type -- a g:type-t type ID with the possible anchestor of gtype or the interface that gtype could conform to

True if the gtype argument is a is-a-type.

If the is-a-type argument is a derivable type, check whether the gtype argument is a descendant of is-a-type. If is-a-type is an interface, check whether gtype conforms to it.

(g:type-is-a "gboolean" "gboolean") => T
(g:type-is-a "GBytes" "GBoxed") => T
(g:type-is-a "GApplicationFlags" "GFlags") => T
(g:type-is-a "GApplication" "GObject") => T
(g:type-is-a "GParamBoolean" "GParam") => T