[RFC XI 2.1 - xf86-input-evdev 2/3] Add experimental XI 2.1 multitouch support

Chase Douglas chase.douglas at canonical.com
Thu Dec 2 07:06:01 PST 2010

On 12/01/2010 05:07 PM, Peter Hutterer wrote:
> On Fri, Nov 19, 2010 at 10:58:20AM -0500, Chase Douglas wrote:
>>> on-the-side question that I just thought of: will having
>>> XIDirectTouch/XIDependentTouch on a device be equally limiting as having a
>>> single axis mode in XI 1.x?
>> Can you provide more detail? I don't see the parallel yet.
>> If you're thinking that each touch axis valuator could have it's own
>> direct/dependent mode, I don't really understand what that would mean.
> well, I guess 20 years ago they didn't think that having devices that are
> both absolute and relative was unlikely :)
> same thing here. best example I can think of right now is a MT tablet that
> has a touchstrip like the Intuos3. the latter would be relative to the
> pointer position.

We could support this through per-axis modes, but I think that would get
hairy. We would have to enforce the X and Y axes to be the same mode.
Then we would need some sort of distinction between the strip valuators
and the touchscreen valuators. They both may support pressure data, for
example, with different resolutions and such. And what would be the mode
of the non-positional axes like pressure?

Instead, we could create separate input devices for the strip and the
touchscreen. The strip would be a dependent device, and would usually be
attached to the same MD as the touch screen. However, it could also be
attached to a different MD, allowing for more interesting mixing and
matching of input devices.

-- Chase

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