queue expose translations after the actual pixel copy

queue expose translations after the actual pixel copy

The expose translation is useful for tracking how outstanding
invalid (exposed on server) areas are copied, and how we need to
compensate for that on the client side to redraw the right area.

So, we should queue the translation at the time we actually move
the bits on the server side, not when moving the window on the
client side.

Also, clean up some naming of parameters.