g-type-check-instance-type (instance gtype)

instance -- a g-type-instance structure
gtype -- the g-type ID to be checked

True on success.

Checks if instance is an instance of the type identified by gtype or derived. This function should only be used in type implementations.

(g-type-check-instance-type (make-instance 'gtk-button) "GObject") => T
(g-type-check-instance-type (make-instance 'gtk-button) "GtkWindow") => NIL