Comment 19 for bug 1633284

At first
https://bazaar.launchpad.net/~onboard/onboard/trunk/revision/2188
then
https://bazaar.launchpad.net/~onboard/onboard/trunk/revision/2192

sz, sz_mm = get_monitor_dimensions(window)
returns (0,0) for sz on your system.

From the debug log:
17:30:42.223 DEBUG KbdWindow _cb_realize_event, screen size 0x0
17:30:42.223 DEBUG KbdWindow _cb_realize_event, monitor dimensions: (0, 0) pixel, (508, 286) mm
17:30:42.223 DEBUG KbdWindow _cb_realize_event, get_min_window_size(): 0 0

Why? I don't know. Only that it must be really rare. Yours is the first case I heard from.

One remaining effect is that the size of label popups might be a bit off. They have a 120 pixel fall-back. If you use them at all, you can override this with
gsettings set org.onboard.keyboard touch-feedback-size 100
for example (in pixel, 0=auto). I should probably add a slider to preferences.

Oh, and I have a slightly better uninstall:
sudo ./setup.py install --record files.txt
sudo xargs --delimiter='\n' -a files.txt rm -v
sudo rm -rf /usr/local/share/onboard

The previous one still left stuff behind that could cause startup failures.

The remaining warnings are "normal". Onboard doesn't actively freeze any windows.

Thanks for your patience again, it's always a pleasure to work with Arch people.