[PATCH 00/15] weston scaling support

[Pekka Paalanen]

On Tue, 28 May 2013 15:10:53 +0200
John Kåre Alsaker <john.kare.alsaker at gmail.com> wrote:

> On Thu, May 23, 2013 at 2:57 AM, Kristian Høgsberg <hoegsberg at gmail.com>wrote:
> 
> > I read through the latest wayland protocol patches and the discussion
> > around them and didn't seen anything I didn't like.  I think the
> > approach here is good and agree with the consensus.  This patch series
> > looks great too and I like the improvements to the pixman renderer and
> > the compositor-x11.c optimization.
> >
> Where did the consensus come from?
> 
> I think the lack of fractional scale factors will result in further
> extensions to support that in the future. I really also dislike how this
> implementation won't allow clients to draw with pixel precision on scaling
> factors above 1.

Quite the contrary, it does allow drawing at least at pel precision, and
it even guarantees that a pel always accurately hits the pixel
boundaries in both the buffer, and all outputs regardless of their
scale factor (provided the compositor does not do additional
transformations of its own).

Introduce rational factors, and it can only be of worse image quality,
combined with a lot of protocol and interpretation difficulties, when
sizes are suddenly not integers.

If you really need an output scaling factor like 1.5, then you report it
as either 1 or 2, and do a compensating scaling in the compositor to
achieve 1.5. That is the best compromize I can imagine, since to be
honest, 1.5 does not work for the protocol nor the clients' rendering.

I thought I explained that before, maybe to someone else, but on this
mailing list anyway.


- pq