Independent clone mode

[Pekka Paalanen]

On Thu, 25 Jul 2019 13:00:55 +1200
Barry Song <21cnbao at gmail.com> wrote:

> Pekka Paalanen <ppaalanen at gmail.com> 于2019年7月24日周三 下午8:10写道：
> >
> > On Wed, 24 Jul 2019 13:22:43 +0800
> > zou lan <nancy.lan.zou at gmail.com> wrote:
> >  
> > > Hi pekka
> > >
> > > I see the clone mode is supported from this commit message.
> > > https://patchwork.freedesktop.org/patch/227970/
> > >
> > > I also see the message  "Independent CRTC clone mode cannot be supported
> > > until output layout logic is moved from libweston into the frontend and
> > > libweston's damage tracking issues stemming from overlapping outputs are
> > > solved".
> > >
> > > I want to ask is independent CRTC clone mode already supported in Weston  6
> > > or 7? If not,
> > > is there a plan to support it?  
> >
> > Hi,
> >
> > no, that commit message is still accurate. I don't know of any
> > plans to work on independent CRTC clone mode.  
> 
> Pekka,
> any possible workaround do you know to support independent crtc clone
> within weston? right now it is very important product feature.
> for example, force weston to identify only one screen, and sync copy
> the screen to 2nd screen and call the drm api of 2nd screen?

Hi,

you could hack it up to do that, but it would be in no way an
upstreamable solution. It would also hurt display timings because
every repaint would have to wait for both monitors to refresh. Or,
all but one monitor would tear.

A simpler hack would be to create overlapping outputs and
force them repaint fully on every refresh instead of repainting
only the damage. That's not upstreamable either, but the damage
could be hacked with probably a one-liner.


Thanks,
pq
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