A keyhandler for svg

This is an example of a keyhandler for controlling an application in svg. It consists of three files.

class.js. This is an implementation of classes in javascript, ripped out of prototype's html guts and modified.
keyhandler.js. A class that propagates key-events between javascript objects and their corresponding svg-elements. Currently it only changes the fill color of the focused element to green.
example.svg. The demo svg with some simple svg-elements that you can switch focus between with left/right/up/down. Press enter to get the currently selected item.

A javascript object that can get key focus has the following properties:

• It has a variable named dom that refers to a svg-element.
  
• It can have the functions onFocus and onLeaveFocus that are called when it gets or leaves focus.
  

The api of the keyhandler.

• setFocus(x) - give focus to object x.
  
• leaveFocus(x) - leave focus from x. this will also trigger leaveFocus on any children of x.
  
• addKey(x, "a", f) - add key listener function f (which is called in the scope of x) for key 'a' when x (or children of x that hasn't overloaded 'a') have focus.
  
• focusStrip([a, b, c], "left", "right") - specify that you can move focus between a, b, c by using the keys left and right.