Achieving Integer Scaling through GPU composition

Pekka Paalanen ppaalanen at
Tue Jan 21 12:41:45 UTC 2020

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

- 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.

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