 - Investigate the possibility of using the shape extension for true
   transparency.

 - Make the program idempotent.  While we only want one copy per machine (or
   per mixer device) actually adjusting the audio volume, it should be
   possible to have the OSD update on multiple displays.

 - Increase configurability - command line options for selecting the mixer
   device to be used, maybe make the icons and colours user-selectable.

 - Visual feedback showing the recording channel.

 - Implement channel soloing.

 - Improve the icons
