http://bugs.winehq.org/show_bug.cgi?id=58667
--- Comment #3 from Stian Low wineryyyyy@gmail.com --- (In reply to despair.chick from comment #2)
The application treats single finger as a brush stroke, and multi-touch as a single finger, utilizing whichever one might've hit the canvas first.
Thanks for confirming the correct software.
Just in case it's a factor, what's your touchscreen hardware/model?
I don't have a physical touchscreen but maybe a Linux virtual touchscreen app is good enough to reproduce the bug.