[udig-devel] Updates to the ViewportPane Interface

[Emily Gouge <egouge@xxxxxxxxxxxxxxx>]

I'm working on a new pan tool that uses the scroll functionality of the 
canvas to provide a smoother user experience and allow for new tiles to 
be drawn on the screen as you pan (if you are using the tiled rendering 
system).

In order to do this I need to make a few additions to the ViewportPane 
Interface.  The function additions are all related to panning and allow 
the viewport pane to know if it is being panned and perform specific 
updates when it is panned.

Can somebody review before I commit these changes?

Emily