This sets an opaque, named pointer on an object.
The name is specified through a #GQuark (retrived e.g. via
g_quark_from_static_string()), and the pointer
can be gotten back from the @object with g_object_get_qdata()
until the @object is finalized.
Setting a previously set user data pointer, overrides (frees)
the old pointer set, using #NULL as pointer essentially
removes the data stored.
This sets an opaque, named pointer on an object. The name is specified through a #GQuark (retrived e.g. via g_quark_from_static_string()), and the pointer can be gotten back from the @object with g_object_get_qdata() until the @object is finalized. Setting a previously set user data pointer, overrides (frees) the old pointer set, using #NULL as pointer essentially removes the data stored.