That specific area in spice will be changed very soon due to new
requiments that the offscreens will add.
Windows direct draw allow modifying offscreen (or even primary)
surfaces using a pointer giving to the user, this mean we can`t know
what parts of the surface was changed... (In some modes the primary
screen can be changed without we know about this)
We already thought about few algorithems we might want to add to spice
to better address this "changed without notifications surfaces", But it
is still not in a state I can confirm in what direction we will go in
the end (We still need to test most of the cases to know what fit us
best)