Sets a dummy callback for @source. The callback will do nothing, and
if the source expects a #gboolean return value, it will return %TRUE.
(If the source expects any other type of return value, it will return
a 0/%NULL value; whatever g_value_init() initializes a #GValue to for
that type.)
If the source is not one of the standard GLib types, the
@closure_callback and @closure_marshal fields of the #GSourceFuncs
structure must have been filled in with pointers to appropriate
functions.
Sets a dummy callback for @source. The callback will do nothing, and if the source expects a #gboolean return value, it will return %TRUE. (If the source expects any other type of return value, it will return a 0/%NULL value; whatever g_value_init() initializes a #GValue to for that type.)
If the source is not one of the standard GLib types, the @closure_callback and @closure_marshal fields of the #GSourceFuncs structure must have been filled in with pointers to appropriate functions.