Re: GSK review and ideas

[Owen Taylor <otaylor redhat com>]

On Thu, 2016-12-15 at 16:26 +0100, Alexander Larsson wrote:
> This combined with the fact that OpenGL makes it very hard, flickerly
> and generally poorly supported to do damage-style partial updates of
> the front buffer means we should consider always updating the entire
> toplevel each time we paint. This is what games do, and we need to
> make that fast anyway for e.g. the resize case, so we might as well
> always do it. That means we can further simplify clipping in general,
> because then we always start with a rectangle and only clip by rects,
> which i think means we can do the clipping on the GPU.

Just because we need to be able to repaint the whole toplevel quickly
for resizing and other animations, and just because games repaint the
whole scene - that should not drive an assumption that there is no
value to clipped updating. Clipped updating is not done for speed -
it's done to reduce power consumption and to leave resources (GPU, CPU,
memory bandwidth) for other usage.

If a copy of Evolution in the background is using only 25% of system
resources to update a small progress bar at 60fps, that's not "60fps -
success!", that's "2W of power - fail!"

- Owen