Having a multi-touch monitor (DELL P2314T) together with another non-multi-touch output confuses (in my case) the pointer maping – in other words, the pointer (mouse) is not where you touch the screen.

1) Make sure the touch screen is the leftmost monitor. Seems like offset-ing the pointer with xinput does not work (and something is buggy here), but scaling does. Actually that is not entirely true: offseting works with xinput, but in the case of multi-touch screen not being left-most the pointer is thrown to the rightmost pixel on X-axis the moment it’s supposed to appear on the multi-touch screen (this is true only for MT input, not for the actual mouse). If the touch-screen the leftmost, there’s no need to do offset, just proper scaling.

2) use xinput’s “Coordinate Transformation Matrix” to ‘remap’ it correctly:

see wiki.archlinux.org:Calibrating_Touchscreen

and here’s a simple /etc/X11/xorg.conf: