Definition of a callback function mechanism for animation playback.
This callback function will called each frame when user use synchronous play.

A function type used by the recursive, cycling routine,

UF_ASSEM_apply_to_cset(_members)

This type of function takes a tag, and a pointer to the application data.
The function should return a logical result which is used to decide whether
to continue the cycle (TRUE means continue).
It is mainly used as an operator on members of a component set where
the members may be sub-assemblies and where the operation should be
performed on all the sub-assembly's children too.

See UF_ASSEM_apply_to_cset below.