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:
| 1 | $ xinput set-prop "Advanced Silicon S.A CoolTouch(TM) System" --type=float "Coordinate Transformation Matrix" 0.5 0 0 0 1 0  0 0 1 | 
see wiki.archlinux.org:Calibrating_Touchscreen
and here’s a simple /etc/X11/xorg.conf:
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 | Section "ServerLayout"     Identifier     "Layout0"     Screen      0  "Screen0" 0 0     Screen      1  "Screen1" RightOf "Screen0"     InputDevice    "Keyboard0" "CoreKeyboard"     InputDevice    "Mouse0" "CorePointer"     Option         "Xinerama" "0" EndSection Section "Files" EndSection Section "InputDevice"     # generated from default     Identifier     "Mouse0"     Driver         "mouse"     Option         "Protocol" "auto"     Option         "Device" "/dev/psaux"     Option         "Emulate3Buttons" "no"     Option         "ZAxisMapping" "4 5" EndSection Section "InputDevice"     # generated from default     Identifier     "Keyboard0"     Driver         "kbd" EndSection Section "Monitor"     Identifier     "Monitor0"     VendorName     "Unknown"     ModelName      "DELL P2314T"     HorizSync       30.0 - 83.0     VertRefresh     56.0 - 76.0     Option         "DPMS" EndSection Section "Monitor"     Identifier     "Monitor1"     VendorName     "Unknown"     ModelName      "Philips 226V4"     HorizSync       30.0 - 83.0     VertRefresh     56.0 - 76.0 EndSection Section "Device"     Identifier     "Device0"     Driver         "nvidia"     VendorName     "NVIDIA Corporation"     BoardName      "GeForce GTX 960"     BusID          "PCI:1:0:0"     Screen          0 EndSection Section "Device"     Identifier     "Device1"     Driver         "nvidia"     VendorName     "NVIDIA Corporation"     BoardName      "GeForce GTX 960"     BusID          "PCI:1:0:0"     Screen          1 EndSection Section "Screen"     Identifier     "Screen1"     Device         "Device1"     Monitor        "Monitor1"     DefaultDepth    24     Option         "Stereo" "0"     Option         "metamodes" "DVI-I-1: 1920x1080_60 +0+0"     Option         "SLI" "Off"     Option         "MultiGPU" "Off"     Option         "BaseMosaic" "off"     SubSection     "Display"         Depth       24     EndSubSection EndSection Section "Screen"     Identifier     "Screen0"     Device         "Device0"     Monitor        "Monitor0"     DefaultDepth    24     Option         "Stereo" "0"     Option         "nvidiaXineramaInfoOrder" "DFP-5"     Option         "metamodes" "HDMI-0: 1920x1080_60 +0+0"     Option         "SLI" "Off"     Option         "MultiGPU" "Off"     Option         "BaseMosaic" "off"     SubSection     "Display"         Depth       24     EndSubSection EndSection | 

