Make everything works again (except fill_template() which has not been updated).

Everything is now simpler because I remove state/cache attributes like st_pos,
st_target, pctcomp, and thus no longer need to update those variables in a
specific order. Everything now is calculated when needed. Managing state *is*, I
admit, a hard problem in computing.

Things seem to work, including setting 'remaining' in relation to stop() and
start().

Now all I need is to update fill_template().