GNOME 3.22.1 has a feature where the tablet and mouse control two separate cursors. Krita doesn't recognize the tablet cursor as a UI element at all: it doesn't show up in the window at all and attempting to draw with it produces nothing. However, it interacts with the GNOME elements just fine. Reproducible: Always Steps to Reproduce: 1. Download and install GNOME 3.22.1 and Krita on a computer with a Wacom tablet. 2. Open Krita in a GNOME Shell window. 3. Attempt to use the tablet on the Krita window (ignoring elements produced by GNOME itself, such as the bar up top). Actual Results: Krita fails to interact with the tablet at all. Expected Results: Krita treats the tablet cursor identically to the mouse cursor, or is able to draw with the tablet without interacting with the other UI elements. My computer is a Lenovo X201 2-in-1 with a Wacom tablet built into the monitor. Also, I have checked using Krita on MATE and it works as expected.
I'm sorry, but I'm not even going to consider looking into this: patches are welcome, but it's not worth my time to install Gnome something,something.something and try to figure out what it's doing. It's not a bug in krita: it's gnome doing something weirdly non-standard, let the gnome developers add support to relevant applications and toolkits.