Achieving Integer Scaling through GPU composition

uday kiran pichika udaykiran.pichika at
Tue Jan 21 13:24:51 UTC 2020

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
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

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

Uday Kiran

On Tue, Jan 21, 2020 at 6:11 PM Pekka Paalanen <ppaalanen at> wrote:

> On Tue, 21 Jan 2020 14:16:09 +0200
> Pekka Paalanen <ppaalanen at> wrote:
> > On Tue, 21 Jan 2020 16:53:51 +0530
> > uday kiran pichika <udaykiran.pichika at> wrote:
> >
> > > What is present in Weston currently ?
> > >
> > >  I know that there is scaling logic already present in the Weston
> > > compositor in GL composition path.
> > >
> > > *But just wanted to know whether it is Integer scaling as mentioned
> above ?
> > > If not, does it possible to implement Integer Scaling in the
> compositor ?*
> >
> > Hi,
> >
> > yeah, Weston's GL-renderer does pick between NEAREST and LINEAR sampling
> > filters, but I think the conditions do not detect an integer factor,
> > only unity factor, so you probably get NEAREST only without any
> > scaling. This is something that could be fixed, but doing it properly
> > will take effort.
> I found some related issues filed:
> - for computing an end-to-end transformation matrix for analysis so
>   that decision between NEAREST and LINEAR takes all combinations into
>   account:
> - but since that is a high risk change, we need screenshooting based
>   tests in the test suite:
> The latter I have finally started on, now that
> is
> more or less done except for one Mesa bug. This depends on
> which
> should be ready to merge as soon as the release freeze is lifted.
> However, we probably should write screenshooting tests for wp_viewport
> first, as well.
> Thanks,
> pq
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