You might want to read this essay by David Revoy -- it's in bugs.kde.org (https://bugs.kde.org/show_bug.cgi?id=277201), but I think that we need a pointer to it that's more accesible. Here it is:


After a night of thinking about it ( yep, it's really too bad to not use Krita
because of a bad calibration problem ) I spend my morning to inspect and test .
Result :

Big guilties are : Xinput_calibrator / and as usual Linux-Wacom they both
produce a mistake at different level. It was hard to find because I had to
suspect Qt, NvidiaDriver, Xrandr, Xinput, Xorg and read ,have headache over
various (deprecated ) documentations and man page. JUST LOVE IT .

I explain :
===========

First guilty : xsetwacom BottomX/TopX/TopY/BottomY command ( or the new one
'Area MinX MinY MaxX MaxY' ) because it fails to distribute the X calibration
coordinate data to the whole session ; the proove , Krita couldn't access it.
So, I consider it broken. Too bad, I like the way it can change the mapping on
the fly threw a simple script.
So a solution is to configure the calibration directly at Xorg level, and
forgot about Xsetwacom calibration. Xorg need to be rebooted to accept new
calbration change, witch is a regression compare to the simplicity of running
various xsetwacom script when need more than one calibration setup. But ok, if
it's work , I'm not about one more little regression.


Second guilty , and the worse IMO : xinput_calibrator ( last one, compiled from
source ) return after running the calibration this sort of friendly deprecated
info with the value :

""
--> Making the calibration permanent <--
copy the snippet below into '/etc/X11/xorg.conf.d/99-calibration.conf'
Section "InputClass"
Identifier "calibration"
MatchProduct "!!Name_Of_TouchScreen!!"
Option "MinX" "327"
Option "MaxX" "86444"
Option "MinY" "374"
Option "MaxY" "65215"
EndSection
""
A bug is filed since month
https://bugs.launchpad.net/ubuntu/+sour ... bug/776946 ; but
reading comments mister tjaalton invalided the bug, and maintain "what I
consider as a mistake" is correct. COOL ONE

So, for my case as in yours if you read this , it will not work :
First, do not use /etc/X11/xorg.conf.d/99-calibration.conf ; Even 'xorg.conf.d'
doesn't exist on Ubuntu/Linux Mint since Lucid Lynx . Prefer to use the
existing 'snippet' in another folder :
/usr/share/X11/xorg.conf.d/50-wacom.conf
I presume it will also work in another new file nammed "99-calibration.conf" ,
edit this with admin right to save it. ( ex: sudo gedit
/usr/share/X11/xorg.conf.d/50-wacom.conf )

The info return by Xinput_calibrator "MinX"/"MinY"/"MaxX"/"MaxY" are also wrong
and will not work with our Wacom tablet who use
"TopX"/"TopY"/"BottomX"/"BottomY" , you should paste them like this between the
existing infos inside the 50-wacom.conf :

Section "InputClass"
Identifier "calibration"
MatchProduct "Wacom|WACOM"
Option "TopX" "327"
Option "TopY" "374"
Option "BottomX" "86436"
Option "BottomY" "65171"
EndSection

Then Save/reboot.

All of this worked for Krita now and whole other apps and system for Linux Mint
10 ( I presume it will be same for Maverick Meerkat , Ubuntu 10.10 ).


Note ; if you use a more recent Linux-Wacom driver I don't think this can work.
I don't know if the Xorg mapping with "TopX"/"TopY"/"BottomX"/"BottomY" will
not be replaced with something looking like :
Option "Area" 319 282 86282 64782
(with your MinX / MinY / MaxX / MaxY value.
In case of doubt just call a clairvoyant to know what are the new name of
values Linux wacom team decided to attribute this time... Of course I joke
just have a look to the documentation here
http://sourceforge.net/apps/mediawiki/l ... alibration
it's updated and works (for the moment).

Now, I presume baking into xorg the coordinate of 2 tablet for the related bug
will also solve it. https://bugs.kde.org/show_bug.cgi?id=276518 but as I ran
out of time, don't use 2 tablet at the moment ; so I will test all this later.