MyPaint only works with pen on multiple monitors if win 10 is set for the SAME SCALING on both monitors (have not tested it with more than two)
Tried v1.0 64, v1.2.0 64 and v1.2.1beta1 32
It gets the pen position wrong (using the wrong scaling I assume). Mouse or finger positioning works correct.
I’m on a 14" 2560x1440 (QHD) touch and pen enabled laptop [X1 Yoga] set for 125% with an external secondary non touch 40" 3840x2160 (QFHD/UHD) display set for 100%.
If both are set to the same 100% or 125% pen positioning works just fine
Tried to install “Gimp 2.8.18”, “Pinta 1.6” and “Inkscape 0.91” that all are supposedly GTK+ based too, and they do NOT have the same issue, so does not sound like the issue is in the GTK+
ADD more details. The scaling is done from the lower left of the screen.
It does not matter which display I set for primary/secondary
if the scaling factor is the same on both displays everything is OK
If the scaling factor on my pen display is LARGER than on the secondary, then the actually point addressed is further away from the lower left by the RATIO of the two scaling factors, (both X and Y).
If the scaling factor on my pen display is SMALLER, then X only(!!!) gets closer to the left edge, I can’t figure out by what factor, but dependant on both scaling factors, but not JUST the ratio… (Y is correct though!)