Input and games.

[Rick Yorgason]

Daniel Stone and Pekka Paalanen wrote:
> ...a bunch of stuff about per-player keyboards and wl_seats...

Okay, let's go over some typical situations:

* It's common for controllers to have keyboard and/or headset attachments,
and built-in touch screens are becoming more common. These are clearly
intended to be associated with the gamepad, rather than the computer.

* Advanced users may want to emulate this connection by plugging extra
devices straight into their computer instead of into their gamepad, and
would need some way to associate those devices with the gamepad.

* A gamepad keyboard may be used in a different way than the system
keyboard. For instance, you could have four local players playing
split-screen against a bunch of other players online. Each player should be
able to use their own keyboard attachment to send their own chat messages.

So perhaps all HIDs should have a pad_index (or player_index?). Anything
plugged directly into a controller will get the same pad_index as the
controller, but an advanced configuration screen could allow you to force a
certain pad_index for each device.

Any app which is not controller-aware can blissfully ignore the pad_index,
in which case they'll treat the keyboards or touch screens as aggregate devices.

-Rick-