IIRC GPUs already do a more efficient version of what you're proposing, at least the mobile ones, by using tile-based rendering. Thus only the general area of t

IIRC GPUs already do a more efficient version of what you're proposing, at least the mobile ones, by using tile-based rendering. Thus only the general area of the screen that changes gets modified while the remainder is static. This way you can easily control how many GPU cores are actively changing and thus need power, while you keep the static state in the other cores and they consume negligible power.