How to workaround a FreeCAD and Krita bug with Wacom tablets

20 Apr 2023 21:30 CEST

Yesterday I started my journey with FreeCAD as a substitute for the great Fusion360, but I immediately realized I had a huge issue: it was impossible to use it under Linux with my new Wacom Intuos BT tablet!

The issue is pretty frustrating: there’s a big offset between the Tablet position and the Hot Spot of the pointer, so that when you try to click on an Icon, it clicks on the icon immediately below.

It is pretty strange. The mouse works perfectly, the tablet works perfectly in many other condition, including other similar applications like KiCad.

And the issue is present in both FreeCAD as a FlatPAK, as a AppImage, and in the Ubuntu DEB.

It took me an entire day to find a post reporting a similar issue in obs-studio, but there are similar for Krita and others, and the workaround that fortunately is pretty simple.

The Issue is due to a regression in Qt 5.12.4, that isn’t fixed yet, as reported in the linked bug report.

So this is the workaround: start the app by exporting the following env variable:

$ export QT_XCB_TABLET_LEGACY_COORDINATES=""

You can add it in .bashrc to have it fixed permanently.