multi-touch-dev team mailing list archive

[Rafi Rubin <rafi@xxxxxxxxxxxxxx>]

About evtouch, it looks mostly superfluous with two possible exceptions. 
 First it has a potentially different calibration correction, though it 
looks a bit odd so I don't think that's much of an argument to keep it 
around longer.  Second it might actually handle rotation a bit better 
than evdev.  But the rotation scaling bug in evdev should get worked out 
in the near future.

I think the extra  correction/scaling factors in evdev should permit us 
to compensate until the driver itself swaps the ranges properly.  Which 
gets us back to the question of how users are initiating rotation and if 
that's considered a well supported feature.

I also don't know how much work would be involved in removing all 
references and autoconfigs that point to evtouch.  So I don't know how 
much work removing it would be.



-wacom does not support true multi-touch.  Even the protocol to make the 
driver do gestures is a little bit different and would require effort to 
adjust other kernel drivers to support.  So I don't think any effort 
spent on utilizing wacom for any form of MT support will assist with 
long term plans, and I don't think that its limited support is worth 
seeking even for short term goals.

I've done a bit of drawing tests and do not see an advantage to using 
-wacom even for single touch operation, as compared to -evdev.  For the 
pen, the pressure curve feature does give it a distinct advantage for 
pressure aware drawing (gimp, xournal...), and so I think its worth 
keeping as is.



A user on the forums has asked for help getting his brand new Studio 17 
with N-Trig touch screen working.  Wacom handles resolution a little 
differently than evdev (perhaps the result of knowing the physical 
specifications of every device that the driver is intended to support). 
 The ntrig driver is emitting coordinates on the same logical grid 
(9600x7200), though the physical range is actually larger for the 17" 
screen.  I don't know if the hardware or hid is scaling from physical to 
logical coords, but its really too late to explore switching that for lucid.

In short, evdev should be fine for touch, even if wacom might not be as 
ok.  And for pen, it doesn't come with one, and I don't know if the 
sensor even handles pen input, so that's not a terribly high priority 
concern.

The user has been experiencing extra clicks instead of a smooth drag.  I 
had him collect a dump of events during a sequence of physical actions. 
 I'm currently digging through those to determine if the sensor is 
having trouble and loosing contact or if the driver is toggling touch 
when it shouldn't.



Summary:
More pressure to remove evtouch
evdev over wacom for ntrig touch
wacom for ntrirg pen, for now
wacom not interesting for multi-touch discussion


Rafi