[Wayland-bugs] [Bug 101193] XWayland does not support scaling

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101193

Maciej Piechotka <uzytkownik2 at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         QA Contact|                            |xorg-team at lists.x.org
          Component|weston                      |XWayland

--- Comment #2 from Maciej Piechotka <uzytkownik2 at gmail.com> ---
(In reply to Pekka Paalanen from comment #1)
> First, I don't think this is a Weston issue. Maybe this should be moved to
> Xwayland instead?
> 

I must've click on Weston accidentally as it was next to XWayland.

> As for the scaling protocol mentioned in the GNOME bug report, it does
> exist: wl_viewport.
> 
> *If* Xwayland had some way of knowing that a Window should cover the whole
> output but the size is not a match, it could use wl_viewport to let the
> Wayland compositor do the scaling, which for a fullscreen game would
> hopefully translate into scaling in display hardware rather than a GPU
> rendering pass.
> 
> But, I would also expect problems with input event coordinates if
> wl_viewport is used naively.
> 
> Maybe Xwayland could support multiple resolutions via RandR by programming
> wl_viewport to scale everything back to the native resolution? Setting a
> mode via RandR would then be the trigger for switching the scaling settings
> in Xwayland globally.
> 
> It does feel to me it could be pretty difficult, I don't really know
> Xwayland that well.
> 

Personally I would like the RandR working on XWayland. I have HiDPI display and
the non-HiDPI programs are suboptimal. I'd like to just set 1920x1080 instead
of 4K for them and be done with them. I don't know XWayland that well but I
assume it renders to texture at some point to pass to compositor - I imagine it
could render lower-res texture onto highier-res so to present highier-res image
to compozitor.

> As for Xwayland actually changing the real video modes on hardware, I'd
> rather not have that. Let's not make X11 RandR a Wayland compositor
> configuration interface. Likewise, 'xinput' is not a Wayland compositor
> configuration interface either.

Agree, at least partially. The most annoying thing is when game changes the
resolution on exit of whole desktop. That said it might be needed for
performance to use native resolution in full screen (this would be perf hack
though, not configuration as it). That said I don't know (and most avenues I
have would go under NDA) if this is the case and rendering texture might be
fast enough.

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