Re: Hortizontal mouse "spanning" after 'xrandr -o left'?
From appendix U in the README:
TwinView and rotation can be used together, but rotation affects the entire desktop. This means that the same rotation setting will apply to both display devices in a TwinView pair. Note also that the TwinViewOrientation option applies before rotation does. For example, if you have two screens side-by-side and you want to rotate them, you should set TwinViewOrientation to Above or Below.