Screen Redraws (Surface Redraws, GPU Redraws) in Wayland

[Ryan Sipes]

Hey Daniel,

Thanks for the info! I didn't realize this was higher up the stack. 
Reading Pekka's post now!
	Ryan Sipes
COMMUNITY MANAGER
RYAN at SYSTEM76.COM


On Fri, May 12, 2017 at 11:05 AM, Daniel Stone <daniel at fooishbar.org> 
wrote:
> Hi Ryan,
> 
> On 12 May 2017 at 17:10, Ryan Sipes <ryan at system76.com> wrote:
>> New to Wayland and had a big question. I was curious as to whether 
>> work had gone into when screen redraws were made (they are called 
>> "Surface Redraws" and "GPU Redraws" in Android). I know in Android 
>> this has resulted in better battery life. I'm sure many in this 
>> mailing list know, but what it does is only redraws when changes 
>> have been made. Is this on the roadmap? Has it already been 
>> implemented? I know it was on the roadmap for Mir, so I'm curious if 
>> it is an consideration in Wayland.
>> 
>> Love the work, using Wayland right now with multiple monitors and it 
>> works great!
> 
> Depends what you mean by 'Wayland', I guess! But most servers 
> (Weston, Mutter/GNOME, KWin, Enlightenment) certainly do this. 
> Repaints only happen once per screen refresh cycle (vsync), and also 
> only when client content has changed and requires an update. This 
> timing information is also passed down to clients, who latch on to 
> the clock to themselves only issue redraws once per frame: the 'frame 
> clock' setup was one of the bigger and more invasive changes in 
> GTK+3, but means those (also Qt, Clutter, GL and I think also EFL) 
> clients don't repaint unnecessarily.
> 
> You can find some more on Pekka's blog - it's fairly old, but still 
> goes into some of the details:
> http://ppaalanen.blogspot.co.uk/2015/02/weston-repaint-scheduling.html
> 
> Cheers,
> Daniel
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