rowantran/xp-pen-on-linux.md

## xp-pen-on-linux.md

      
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              xp-pen-on-linux.md
            
          
    Short guide detailing how to use the new drivers included in kernel (since 5.1) for an XP-Pen tablet.
As of 5.1, this method should work for at least the XP-Pen G540 and G640 (I am using a G540 but commands given should be identical
across either tablet.)
Running xinput list should yield something similar to this:
$ xinput list
⎡ Virtual core pointer                          id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ Hoksi Technology DURGOD Taurus K320 Aurora Consumer Control       id=10   [slave  pointer  (2)]
⎜   ↳ Hoksi Technology DURGOD Taurus K320 Aurora Mouse  id=12   [slave  pointer  (2)]
⎜   ↳ UGTABLET TABLET G3 5x4 Mouse              id=13   [slave  pointer  (2)]
⎜   ↳ UGTABLET TABLET G3 5x4 Mouse              id=14   [slave  pointer  (2)]
⎜   ↳ Razer Razer DeathAdder Chroma             id=16   [slave  pointer  (2)]
⎜   ↳ Razer Razer DeathAdder Chroma Consumer Control    id=17   [slave  pointer  (2)]
⎜   ↳ UGTABLET TABLET G3 5x4 Pen Pen (0)        id=25   [slave  pointer  (2)]
⎣ Virtual core keyboard                         id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]
(continues ...)

Look under the "Virtual core pointer" section and take note of the name of the device ending in "Pen" -- in this case that would be
"UGTABLET TABLET G3 5x4 Pen Pen (0)" so that you can use it in the next command.
Running xinput list-props "[INSERT NAME OF DEVICE]" should give a short list of properties, something like this:
$ xinput list-props "UGTABLET TABLET G3 5x4 Pen Pen (0)"
Device 'UGTABLET TABLET G3 5x4 Pen Pen (0)':
        Device Enabled (155):   1
        Coordinate Transformation Matrix (157): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
        Device Node (277):      "/dev/input/event17"
        Device Product ID (278):        10429, 117
        libinput Tablet Tool Pressurecurve (509):       0.000000, 0.000000, 0.000000, 0.000000, 1.000000, 1.000000, 1.000000, 1.000000

The "Coordinate Transformation Matrix" property takes the form of a b c d e f g h i, representing a 3x3 matrix applied to the
input from the tablet. If you use full area, the default matrix of 1 0 0 0 1 0 0 0 1 will map the entire tablet area to the screen.
If you use a portion of the tablet, you will have to do a bit of simple math to calculate some values.
For examples, I will pretend that I am using a 3x1.69 area on a 5x4 tablet.
First, we will calculate the values that represent the area size.
Calculate the value a by dividing total width / width of your area. For example, 5 / 3 = 1.667.
Next, calculate the value e by dividing total height / height of you area. For example, 4 / 1.69 = 2.367.
Now we will calculate the values representing offset.
For horizontal offset, if you want the area to be aligned against the left edge of the tablet, the value of c is 0. If you want it to be aligned against
the right edge of the tablet, the value of c equals 1 - a. This should be a negative number in all cases.
For vertical offset, if you want the area to be aligned against the top edge of the tablet, the value of f is 0. If you want it
to be aligned against the bottom edge of the tablet, the value of f equals 1 - e. This should also be a negative number.
We should now have the values a, c, e, and f. Take those values and run the following command:
$ xinput set-prop "[INSERT NAME OF DEVICE]" "Coordinate Transformation Matrix" a 0 c 0 e f 0 0 1

Replace a, c, e, and f with the values calculated above. Your tablet should now use your desired area.