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  1. Qt
  2. QTBUG-137091

QTabletEvent::pressure() capped at ~0.474 under X11/xcb QPA, despite raw ABS_PRESSURE = 0–8191

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    • Icon: Bug Bug
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    • None
    • 5.12.8
    • OS: Ubuntu 20.04 (kernel 5.15.0-139)
      Tablet Hardware: XP Pen Artist 16 2nd Gen
      XP-Pen Driver Version: 4.0.7 (7c4a501)
    • Linux/X11

      This bug was originally reported on Krita's site.

      Steps to Reproduce

      1. Hook up XP Pen tablet and start driver

       

      2. Run `evtest` to show the raw pressure output from the driver

        First identify the device by running `evtest`, and select the correct device

        Then check the values from that event.

       

      # i.e
      sudo evtest /dev/input/event25

       

      3. Press on the tablet and watch the values ranges from 0-8191 as expected

       

      4. Compile and run the attached `pressure_printer.cpp`

       

      g++ -std=c++17 -fPIC pressure_printer.cpp -o pressure_printer \
          $(pkg-config --cflags --libs Qt5Widgets)
      

      Run ./pressure_printer and then press your pen down on the white square that pops up.

      Note the pressure value is maxed out at ~0.474

      This can also be demonstrated by using the Tablet Tester in Krita (Settings > Configure Krita > Tablet Settings > Open Tablet Tester)

       

      What should have happened

      The value should have reached 1.0 as the pressure increased to the max value of 8191

       

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            liaqi Liang Qi
            _rm_ Reed Morris
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              Created:
              Updated:
              Resolved:

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