Paint() now takes the bounds of a rectangle of visibility.  This means that Resize() and friends can redraw the entire tickertape (which is probably easiest), but that Tick() can shift the offscreen pixmap and just update the edge.
Paint() now takes the bounds of a rectangle of visibility.  This means
that Resize() and friends can redraw the entire tickertape (which is
probably easiest), but that Tick() can shift the offscreen pixmap and
just update the edge.

tphelps/xtickertape,epronk/xtickertape,tphelps/xtickertape,tphelps/xtickertape,epronk/xtickertape