MyPaint tries to resize panels instead of using controls in them.

[sergey6661313]

Description of the problem

1. MyPaint tries to resize panels instead of using controls in them. So for example, I can't choose a color.
   examples:
   https://www.youtube.com/watch?v=pM7pQmxs0-s
   https://www.youtube.com/watch?v=hHPA5PkYUSk
2. when choosing the thickness and other parameters of the brush with the mouse, and then taking the stylus and bringing it to the tablet, the settings are switched. I did not set them up to make them stray.
3. same problem when using different brushes for MyPaint. Each brush resets all settings for me.

Basic system details

MyPaint version: 2.0.1+gitexport.478280f (installed from AUR in arch)
Operating system: Arch x86_64
Desktop environment: X11 KDE
Device: huion pen tablet WH1409(8192)
(config: https://cdn.discordapp.com/attachments/653178334103994370/951161531565998090/unknown.png)

Steps to reproduce

1. Start MyPaint
2. just draw or touch about (or inside) any panels.

(mypaint:17102): Gtk-CRITICAL **: 20:05:35.119: _gtk_widget_captured_event: assertion 'WIDGET_REALIZED_FOR_EVENT (widget, event)' failed

[odysseywestra]

Can't reproduce it with my Wacom 13HD, and PTH-651 with Gnome Shell so it might be a DE specific issue, but curious to note is that your stylus is recognized as a touchscreen than a pen or mouse. Touchscreens may have a wider "cursor" I would say on KDE than Gnome Shell. So maybe look into what xinput or your kernel drivers to see what it's outputting there cause MyPaint get its input info from GDK which is from libinput which uses xinput to configure it with Xorg. I'll still test around and maybe boot up a drive that had KDE on it and see if I can reproduce with my hardware.