Determine the X Display edge in a multi X screen configuration

[Jim Westfall]

Hi

I'm wanting to determine when the mouse pointer is near the edge of the X 
Display.  

In the case when there is only one X screen, the edge of the X screen 
will be the edge of the X Display.  However when multiple separate X 
screens (zaphod) make up the X Display using this method is not 
possible.  For each X screen, there will be at least one edge that is 
adjacent to another X screen.  As such those edges are not the edge of the 
X display.

Originally I figured I would just be able to query the X server for 
details about the arrangement of the X screens and from that figure out 
the adjacent X screen edges.  However I've been unable to find any function 
that provides this information.  Does such a function exist? and/or is 
there some better way to determine if a given X screen edge is the edge of 
the X display?

thanks
Jim