On Wed, 2017-04-05 at 10:53 +0100, Daniel Stone wrote: > Hi Steven, > > On 5 April 2017 at 10:42, Steven Newbury <[email protected]> > wrote: > > On Wed, 2017-04-05 at 10:25 +0100, Daniel Stone wrote: > > > The compositor _must_ interpose every single keyboard/mouse > > > event, > > > and > > > they are simple enough that it is possibly to easily encode them > > > with > > > universally-accepted concepts. Neither is true of gamepads or > > > joysticks. Hence, a different protocol. > > > > 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. Arbitration > > between desktop use and focused application utilising inputfd is > > the > > issue IMHO, and as Carsten says, I don't see why that is any > > different > > than if a game controller is your primary input device. > > DGA's DirectMouse doesn't change the latency. It doesn't give the > client a direct-to-kernel stream. It still results in the server > doing I wondered if I was implying that too strongly as I wrote it, I know it didn't provide a direct-to-kernel stream. Are you sure it didn't also reduce latency though, even if only because it skipped the acceleration code as you mention below? I suppose latency was bounded by the main thread?
> some light internal processing in a signal handler, placing them on a
> queue, waiting to wake up, and then posting them to the client from
> the main thread. Its actual benefit was to give clients access to
> unaccelerated relative motion vectors. So the relative/confined
> pointer protocols put us on a par with 'DirectMouse' already there.
It's certainly sufficient for most use cases. Are you sure about
DirectMouse parity?
>
> I would suggest it only outlasted the direct framebuffer access
> because we later got DRI{1,2,3} for free with GL games, and because
> unlike direct framebuffer access, it wasn't catastrophically broken
> by
> later hardware.
Yes, of course. DGA direct framebuffer access was pretty useless as a
graphics API.
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