Yeah, some mobile GPUs actually have hardware compositors that can do. They can even support moving windows around with pretty low overhead. But the software s

Yeah, some mobile GPUs actually have hardware compositors that can do. They can even support moving windows around with pretty low overhead. But the software support to take advantage of it isn't really there. There isn't a standard API to access such functionality, and so the hardware compositors end up unused, so the don't really put much effort into improving them. But with proper software support and a hardware compositor with enough flexibility, you could easily put the clock in it's own texture and update it with very low power consumption. Actually, Desktop GPUs already have a single hardware sprite that gets used for moving the mouse cursor around with very little overhead (and lower latency).