[RFC wayland-protocols] inputfd - direct input access protocol

Steven Newbury steve at snewbury.org.uk
Wed Apr 5 10:15:05 UTC 2017

On Wed, 2017-04-05 at 11:57 +0200, Bastien Nocera wrote:
> On Wed, 2017-04-05 at 10:42 +0100, Steven Newbury wrote:
> > 
> <snip>
> > There's a reason the mouse support from the X DGA Extension out-
> > survived the "direct framebuffer access".  The latency through the
> > wire
> > whether X or Wayland for mouse input it just too high for mouse
> > controlled high framerate 3D games.  inputfd *will* be wanted for
> > mice,
> > and unlike keyboard there isn't the issue of state.
> SDL2 doesn't use the DGA extension, which makes me think that it's
> not
> as much of a problem as when running Doom in X in the 90's.
AFAIK SDL2 uses the Xinput2 extension for pointer/relative mouse
devices nowadays, which with current Xorg is on its own input thread
which helps a lot.  That said, gamers do claim better latency from
Windows DirectX than Xorg.

> That being said, I see no reason why the compositor couldn't consider
> the mouse to be a "gaming device" when a number of conditions are
> met,
> such as the application being fullscreen, and the mouse having been
> grabbed.
> The compositor could then yank this device out of the application's
> reach when unfullscreened, or the grab broken. Again, this is the
> compositor's choice. And I'm certain that we'd extend most
> compositors
> that way if game developers requested the functionality.
Probably benchmarking the difference would suggest whether it's
worthwhile or not.
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