Prototype of the progress function used to compute the value
between the two ends a and b of an interval depending on
the value of progress.
The #GValue in retval is already initialized with the same
type as a and b.
This function will be called by #ClutterInterval if the
type of the values of the interval was registered using
clutter_interval_register_progress_func().
Prototype of the progress function used to compute the value between the two ends
aandbof an interval depending on the value ofprogress.The #GValue in
retvalis already initialized with the same type asaandb.This function will be called by #ClutterInterval if the type of the values of the interval was registered using clutter_interval_register_progress_func().