revMobile: backbutton graphic geometry

[David Bovill]

So how to make a flexible backbutton - those rounded rectangles with a
pointy end?

   1. Use several images like you would on the web - prob = hack + difficult
   to scale vertically
   2. Use several groups in some fiendishly clever way
   3. Use a graphic and work out the points to create the desired shape

I'd like to be able to scale the button horizontally and tweek it
vertically. What's the best technique and if the aim is to use points based
geometry what would the function look like to create / transform it?