Achieving Integer Scaling through GPU composition

[uday kiran pichika]

On Tue, Jan 21, 2020 at 7:35 PM Pekka Paalanen <ppaalanen at gmail.com> wrote:

> On Tue, 21 Jan 2020 18:54:51 +0530
> uday kiran pichika <udaykiran.pichika at gmail.com> 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.
>
> Hi,
>
> alright.
>
> > 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?
>
> https://patchwork.freedesktop.org/series/68378/ is one revision of it,
> I'm not sure if it is still the latest.
>

I'm aware of these patches and some enhancements are being made on top of
these. Changes are under validation. It may take some more time to float
the patches on top of these.

>
> > 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.
>

When referrring to fractional scaling for HiDPI screens, i think wayland is
already providing the support as per the below link. Not very sure whether
this is implemented in weston compositor.
https://wiki.archlinux.org/index.php/HiDPI

can you please elaborate on the below line from your comment "happens
mostly behind the client's back" ? do you mean that the client does not
aware how the scaling is happening down the line ?


>
> > 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.
>

Sure Pekka. I will check for other compositor which can helpful in the
desktop environment.

>
>
> Thanks,
> pq
>
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