Attached is a patch which adds a feature to xxdiff which is available in xdiff on AIX, and possibly others.
With this patch a click on the diff overview area on the right hand side of the window causes the diff view to jump to the approximate area of the diff.
Patch for click-to-jump on overview
I'm porting xxdiff to Qt4 and I integrated your patch in the code. Let's hope now that Martin will bring my code in his reference :-)
xxdiff 4.0b1 available with your patch.