Re: [Linuxwacom-discuss] calibrating a Cintiq in a dual monitor setup?

[Jason a. <ala...@gm...>]

On Wed, Jan 4, 2012 at 5:48 AM, Jason Gerecke <kil...@gm...> wrote:
> On Tue, Jan 3, 2012 at 1:58 AM, Jason alavaliant <ala...@gm...> wrote:
>> Hi,
>>
>> I know how to calibrate a Cintiq in Linux when it's the only monitor
>> attached to the computer.   However what if there is a second monitor
>> attached as well (twinview using 'Coordinate Transformation Matrix' to
>> map to the Cintiq) the values needed for calibration are quite
>> different.
>>
>> For example with the Cintiq I was testing with;
>>
>> 0, 0, 86680, 54180
>> is the default tablet area
>>
>> 0, 0, 86680, 62180
>> seems to be the right values for just having Cintiq connected.
>>
>> However if I have a second monitor attached on the left and map the
>> tablet to the right monitor only using Coordinate Transformation
>> Matrix values I have to use
>> 808, 365, 87419, 54407
>> (worked out very slowly by hand by changing values bit by bit by hand)
>> is what is needed to make the calibration line up.       I'm sure
>> there is a way to calculate these values directly but so far how to do
>> it is escaping me.   Has anybody out there worked out the sums
>> required?
>>
>> Thanks
>> -J
>>
>
> The calibration shouldn't need to be changed if the proper Coordinate
> Transformation Matrix is used. The raw coordinates from the tablet are
> first scaled according to calibration and then transformed onto the
> proper monitor by the X server with the matrix.
>
> Can you provide the output of the command 'xrandr', as well as the
> value of the Coordinate Transformation Matrix?
>
> Jason
>

hmm interesting,  I think I have the transform matrix correct.  I
can't give you the exact values (since I don't have the Cintiq on
hand, it's not mine, I'm just helping the owner set things up), I use
the same formula to workout the values on all computers so on another
similar setup I have;

left monitor;  1280 x 1024
right monitor; 1680 x 1050
(We are using the nvidia proprietary driver so I don't think xrandr
would give you much useful info since it doesn't support randr 1.2 )

with
Coordinate Transformation Matrix (119): 0.567568, 0.000000, 0.432432,
0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
to map the tablet onto the right monitor.  Which looks to work fine
with Intuos tablets I normally work with.

-J