Achieving Integer Scaling through GPU composition

Pekka Paalanen ppaalanen at
Tue Jan 21 14:05:02 UTC 2020

On Tue, 21 Jan 2020 18:54:51 +0530
uday kiran pichika <udaykiran.pichika at> wrote:

> Thanks Pekka for your reply.
> I work for an OEM company. We have given the support of Integer Scaling
> though NN in Windows environment though System Settings.
> So we are providing the similar support even in Linux environment as well.
> This is the reason, I have chosen Weston compositor as a POC for Integer
> Scaling through NN.



> And our Display hardware supports the Scaling with multiple scaling
> filters. If we make the modifications to do the support with DRM planes, we
> should consider the fallback option as well. So the default fallback is GPU
> composition.

Yes, indeed. Are you aware of the on-going work in the kernel or
perhaps participating in it? is one revision of it,
I'm not sure if it is still the latest.

> In order to provide the support to GPU composition, have started exploring
> this Integer Scaling functionality in GL composition.
> As per your comments, App can't inform to the compositor about the Integer
> Scaling for a specific window until and unless we should add an extra
> variable or some request to the surface. I think this is very bad idea of
> adding.

Right. Expecting a compositor to show your window unchanged is somewhat
reasonable, but adding protocol to control the details of how a
compositor should composite your surfaces becomes awkward fast on the
usual desktop.

I say somewhat reasonable, because things like fractional scaling,
referring to HiDPI support with non-integer scaling factors, is a thing
and happens mostly behind the client's back.

> can you please suggest, any other compositor which we can chose for the
> desktop functionality ?

Pick any desktop environment on Linux that uses Wayland under the hood,
and it will have its own compositor.

Weston is fine if you want to experiment with new technology, if you
need to prove a new kernel UAPI, or if you have an embedded system use
case. But if you aim for end users' desktops, then Weston does not
provide for that.

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