I came across this piece of code:
http://processing.org/hacks/hacks:clickedmousepos

I tried implementing it into a sketch:

void setMouseXY()
{
 if(mouseX>=0 && mouseX<width && mouseY>=0 && mouseY<height) return;
 Point mouse, winloc;
 mouse = MouseInfo.getPointerInfo().getLocation();
 winloc = frame.getLocation();
 if(!frame.isUndecorated()){
   winloc.x += 3;
   winloc.y += 29;
 }
 mouseX = mouse.x-winloc.x;
 mouseY = mouse.y-winloc.y;
}

void setup()
{
 size(400, 400, P3D);
}

void draw()
{
 setMouseXY();
 println("\nx: " + mouseX + " y: " + mouseY);

}

When I try to compile, it gives the error:
Semantic Error: No accessible field named "MouseInfo" was found in type "Temporary_6179_3999".

A search on "No accessible field" led me to:
http://mobile.processing.org/discourse/YaBB.cgi?board=syntax;action=display;num=1177102386

According to that site, this error is triggered when trying to use a variable out of scope.  I'm not sure how I can get MouseInfo to be in scope, though, I'm not familiar with Java.

Any advice on how I can get this code to work, or achieve the same effect through another means, would be appreciated.

Thank you for your help!  You were right about the version of Processing, turns out I had an old one.  Updating fixed the compile/run issue.

I wasn't aware of that mouseX/mouseY were meant to be read-only, I'll keep that in mind.  I'm guessing that may cause me trouble later on when trying to use Robot.  I'm assuming the variables aren't read-only yet, but will be sometime in the future?  Because the code does work, which I'm guessing it wouldn't if the variables were read-only.

Regarding the hard-coded border/title sizes, that Insets example looks like it will be very useful, and I would eventually have wanted to resize a window on the fly as well.

Thanks again, I should be able to move on to the fun parts of my project after getting the input out of the way, and I'm looking forward to that.