evdev-grail problem with multitouch driver in Ubuntu 10.10

[Vincent Gerris]

Dear Xorg developers,

As a humble Ubuntu 10.10 user I found my tablet Pc not working under 10.10.
After some googling I met the friendly kernel-developer Stéphane Chatty, who
developed a driver which I helped testing.
The driver seems to work very well (thank you Stéphane !).

Canonical decided to change some things to Xorg to get multitouch working.
We noticed this, because the first version of the driver did not sent events
for mtX and mtY.
After those events (53 and 54 I believe) where enable, I started noticing
tearing and slow responses or no responses to tapping the screen.

I noticed from exploring Xorg.0.log there was this message:
*evdev*-*grail*: failed to open grail, no gesture support

This message was gone after the MT-events were sent, so I figured
evdev-grail was causing the slow responses.
I can confirm that now: I installed Ubuntu 10.04 with the Maverick (10.10)
kernel and compiled and loaded the driver and there is no more tearing.
The Xorg version on 10.04 does not use evdev-grail , which is used in 10.10
for utouch.

>From what I understand, this evdev-grail is used to enable gestures until
there is a more structural solution.
I notified Chase Douglas on launchpad of my experience too.

My question to you is: can this behaviour be tweaked so the device will be
responsive?
Also I would like to notify you of this problem by this mail and ask for
your advice: should Ubuntu really implement this?
Currently it definitely leads to a bad user experience at is not really
usable.

I am willing to test any suggestions. Please note I am mostly a user who can
compile a kernel and modules.
I do have some coding knowledge, but barely C, so the code is not too
comprehensible for me (yet) :).

Thank you for any help!

Kind regards,
Vincent
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