To specify the placement of each animcomp relative to its controlling
animob, you set the animcomp members xtrans and ytrans.  these values can
be positive or negative.

The system is designed so that only one of the animcomps in any given
sequence is "active" (being displayed) at a given point in time.  It is
the only image in the sequence that is (or is about to be) linked into the
gelsinfo list. the timer determines how long each component in the
sequence remains active, as described below.