Gamepad focus model (Re: Input and games.)

[Pekka Paalanen]

On Mon, 13 May 2013 09:12:03 +1000
Peter Hutterer <peter.hutterer at who-t.net> wrote:

> On Fri, May 10, 2013 at 10:41:45AM +0300, Pekka Paalanen wrote:
> > On Thu, 9 May 2013 16:44:09 +1000
> > Peter Hutterer <peter.hutterer at who-t.net> wrote:
> > 
> > > On Mon, May 06, 2013 at 03:36:20PM +0300, Pekka Paalanen wrote:
> > > [...]
> > > > I had a private chat with Daniel, and we came to an understanding,
> > > > which I try to describe below. The interface names below are more like
> > > > placeholders for now.
> > > > 
> > > > Into wl_seat, we should add a capability bit for gamepad. When the bit
> > > > is set, a client can send wl_seat::get_gamepad_manager request, which
> > > > creates a new wl_gamepad_manager object. (Do we actually need a
> > > > capability bit?)
> > > > 
> > > > A wl_gamepad_manager will send an event for each physical gamepad (as
> > > > it dynamically appears, if hotplugged later) associated with this
> > > > particular wl_seat, creating a wl_gamepad object for each.
> > > > 
> > > > A wl_gamepad object will send an event about the player id as the first
> > > > thing, and also if it later changes.
> > > 
> > > do you expect the player ID to be exposed on the protocol?
> > > what does it contain and who manages the association?
> > > is it related to any physical ID of the gamepad, and if not, can such ID be
> > > provided (if the device supports it)?
> > 
> > I imagined the player ID to be sent explicitly in the protocol, with
> > its very own event. The server would manage the association between
> > physical devices and the player ID, according to built-in heuristics
> > and user preferences.
> > 
> > E.g. if one goes from 0 gamepads to 1 gamepad, it will always be player
> > 1; or maybe take the first player slot that does not have a gamepad,
> > unless we identify the device as the same that was recently unplugged
> > in which case take the player slot that it used to have. Or something,
> > with user preferences, and some UI to fix the association in the rare
> > case when the heuristics choose wrong.
> > 
> > Recognizing a gamepad could be done via physical identification, if one
> > is available, or by usb port/hub, or whatever platform specific way.
> > The clients would not have to care, they would only work with unique
> > player IDs, which are integers created in sequence starting from 1 (or
> > 0).
> 
> first - I agree with player ID being assigned to a gamepad for the simple
> reason of giving all clients a baseline.
> 
> I think that phys information should be exposed in some way. use-case here
> is a specific controller that is always owned by the same human player. the
> game could then associate this automatically with the player.
> this could be a later addition to the protocol though, because right now I
> have no idea how to do this sensibly.

Wouldn't that be better configured in the server, rather than in every
game?

But yeah, I don't even have any idea what should be exposed as physical
info.

> > Using integers starting from 1 makes it trivial for the server to
> > update the player ID display on the gamepads, if they have one.
> > 
> > The server could also implement a global UI to reassing gamepads. For
> > instance, press the famous home button for 5 secs on any gamepad, get
> > some gamepad controllable GUI to reassing them, or maybe just a request
> > to press the home button again on each gamepad in sequence.
> 
> this UI could also handle the seat assignment, see below.
> 
> > Doing all this client side would mean we need to find a way to
> > communicate all the device and platform specific hints for the gamepad
> > assignment heuristics somehow, and each client instance would have its
> > own gamepad assignments.
> > 
> > > is the player ID not better represented through a wl_seat? - if you're
> > > playing a full-screen game, both seats can safely have the same focus,
> > > otherwise, players can play games independently.
> > > plus, if both players have a separate seat, they can use their keyboard
> > > independently for data entry.
> > 
> > Those were exactly my thoughts in the beginning, however during the way
> > long email thread, I got convinced otherwise for now. There are a few
> > issues that come mind:
> > - how to know, when one seat should follow the keyboard(?) focus of
> >   another seat?
> 
> I wonder when this is necessary. unless I'm misunderstanding something this
> should only be of concern when both users want to change games (or otherwise
> between clients)?

I would imagine, that two players each with own gamepads is a more
common case when playing the same game on split-screen or alike, than
playing two different games. Therefore, when the game is started, the
display server would ideally somehow know to assing both gamepad foci
to the game window.

The basic assumption with seats is that each is independent, but the
server is of course free to assign foci as it chooses. This is just a
server implementation detail.

But I guess it does not really matter how it is on the protocol level,
there would need to be a "focus group" configuration in the server
anyway; either by protocol allowing several gamepad in one wl_seat, or
a purely server detail by focus groups containing wl_seats.

I think this is not a protocol question as much as a server
implementation consideration, so... *shrug*.

> > - a client still needs to map seats into players; how? does it need an
> >   UI to fix it in case a user is not happy with the result?
> 
> well, tbh if you're planning for multiple seats at some point you'll need a
> UI to handle it anyway. whether this is for ptr/kbd seats or gamepads, it
> comes down to the same. but even with the proposal above you still need some
> UI anyway.

Yeah, but my question is, is it enough to have a UI in the server, or
does every game need one, too? Or do games need one in any case for
other reasons, so it's not a really an issue?

> also, afaict this is what some game consoles have, e.g. the Wii associates
> your controller with your Me.

What is "Me"?

I get the feeling there might be some more complex use case behind what
you wrote. Is it perhaps players storing/associating their online
player ID with their personal gamepad or something?


Thanks,
pq