Yep, what's going on here is that the touchpad communicates its dimensions to the xserver, and then xserver compares that to the screen size and scales mouse movement to correspond to the screen. Most of the time that matches expectations, but when the aspect ratio of the screen differs significantly from the aspect ratio of the touchpad, it can produce weird results.
In I've coded a patch to add a way to turn off this behavior, via either an xinput property "Resolution Detect", or an xorg.conf option. * Add 116_resolution_detect_option.patch: Provide an option to prevent synaptics from communicating the touchpad size to the xserver. This can be used to solve problems where differences in touchpad and screen dimensions cause the mouse pointer to skip pixels when moving. (LP: #327428) ** Changed in: xserver-xorg-input-synaptics (Ubuntu) Status: Incomplete => Fix Released -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-input-synaptics in ubuntu. https://bugs.launchpad.net/bugs/591954 Title: Touchpad aspect ratio changes with TwinView _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp