There is one problem with Xsp. It is inherently unsafe. You turn pixel doubling on and off and it has global effect but you're not guaranteed to be the only one updating the screen. Any random system screen update (even in full screen - infoprint, task navigator menu, ...) can mess up the screen to the point you need to reboot to see anything again. Otherwise it mostly works :-) In OS2006 it was enough to turn it on, blit the rectangle via SDL and then turn it off again, in OS2007 it didn't work for me and output was not pixel doubled until I turned it on and left it on. One can then check SDL focus lost event to turn it off but it was not fast enough for me, the menu popped up by home key was faster when I tried :-(

The safe way is how mplayer does it, use direct framebuffer ioctl for screen update. This update has pixeldoubling flag which is valid only for that specific screen update.

Would be nice to have optimized SDL for current line of tablets with such direct framebuffer stuff. Sadly there is no time, only ideas.