It would solve a heap of issues if we had a two dimentional slider - you can define MAX values according to requirements of application like, 180 for degrees of a servo or 1024 pixels of a screen you are pointing to etc.
Grab the pointer and a stream of data frm a move event giving both values (or even better, only changed values) would solve all sorts of joystick / pointing type issues.
Just as a curiousity,
You are aware of the single dimension slide (default horizontal) can also be configured vertical.
This gives two dimensions, albeit not simultaneously - but may be of some use to know.
Your Feature Request has been noted.