[RFC] MPX XInput Protocol extensions - big issues....

Jim Gettys jg at laptop.org
Mon Mar 3 15:30:02 PST 2008

Some comments:

Big questions:

How will we associate users with input devices?  We'll certainly be
dealing with input devices that can identify who is using them (e.g.
Diamond Touch, remote devices, etc.) 

How will that interact with Eamon's security framework?

I can see (at least) two possibilities:
	1) events might include a field to identify who owns the device
	2) we might include the identity of the owner of the device as part of
the device on query, and identify whenever the owner of a device changes
as an event.

Should we introduce the user as a first class object?

How is this intended to work with ChangeWindowAccess?

Other question:

Xi's valuators lack names, so you don't know whether the first valuator
is "x", or "y", or "z", or "pressure", etc.  Are we intending to fix
this (major) oversight?  If so, how?

			Best regards,
                                - Jim

On Mon, 2008-02-25 at 17:53 +1030, Peter Hutterer wrote:
> I did my homework and wrote up the XI protocol message specifications 
> that will be in the first merged version of MPX (April 08 probably).
> The document resembles the format used in the X Protocol Reference 
> Manual (Nye, 1994).
> HTML version: http://people.freedesktop.org/~whot/Xi/
> PDF version: http://people.freedesktop.org/~whot/Xi/mpx_xi_protocol.pdf
> Short overview of the new requests:
> - ListInputDevices
>    + a previously used padding field now specifies the attachment/pairing
>    + use field changed
> - QueryDevicePointer
>    + same as QueryPointer but specifies the device.
> - WarpDevicePointer
>    + same as WarpPointer but specifies the device.
> - ChangeDeviceCursor
>    + specify cursor shape for device
> - ChangeDeviceHierarchy
>    + create/remove new master devices
>    + change attachment of slave devices
> - ChangeWindowAccess
>    + change access rules for devices on a given window. useful for 
> multi-user GUIs. Not a security feature!
> - QueryWindowAccess
>    + query access rules
> - SetClientPointer/GetClientPointer
>    + set the device that is picked when a core request doesn't specify a 
> device.
> - XiSelectEvent
>    + select for generic events
> - ExtendedGrabDevice
>    + grab device, but with generic event masks
> Short overview of new events
> - DeviceEnterNotify, DeviceLeaveNotify (well, guess)
> - DeviceHierarchyChangedEvent
>    + sent as a notification after a ChangeDeviceHierarchy
> - DeviceClassesChangedEvent
>    + sent when the master flips state to reflect a new slave device.
> Again, full documents to be found at:
> HTML version: http://people.freedesktop.org/~whot/Xi/
> PDF version: http://people.freedesktop.org/~whot/Xi/mpx_xi_protocol.pdf
> I will try to get a formal review of the core protocol and the behaviour 
> changes of XI out soon. Meanwhile, please review these additions. Thanks!
> Cheers,
>    Peter
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Jim Gettys
One Laptop Per Child

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