on webos there is a similar project, what do they do: they have the chroot render into a secondary framebuffer (on webos there are two), and display its contents later

now... :0 on sfos (at least on the jolla phone):
there are two framebuffers! /dev/fb0 and /dev/fb1
then, does aliendalvik use the second fb? doesn't seem like it, if we can trust fuser/lsof