Comment 15 for bug 365952

I don't think we can use the edges for this feature. The edges have too much
semantic behaviour that we shouldn't break.

A move that starts inside and crosses an edge does not generate scroll events.
If edge scrolling is disabled, the edge settings are effectively ignored. Plus
there is the circular scrolling and corner-coasting interaction that also
complicates things.

This bug seems to affect all Dell Minis, so it's not just a single machine's
problem.

The patch you submitted before is a good start, but I don't want this to be
just on the bottom edge. Sooner or later it will affect other edges too so we
might as well get it right now.

I propose a "Synaptics Area" optional property that allows for all 4
directions to be limited to a given coordinate value.

The semantics get a bit interesting though:
- if a finger moves from the valid to the blacklisted area, does it continue
  in this area or are all coordinates clipped?
- if a finger starts a move in the blacklisted area, does it generate events?
- If a finger taps in the blacklisted area, does it generate events?