setQdata
This sets an opaque, named pointer on an object. The name is specified through a #GQuark (retrieved 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.
Parameters
quark
A #GQuark, naming the user data pointer
data
An opaque user data pointer