TO DO:

  code:
    Do The Right Thing with respect to row buffers, macros, and inline functions.
    Have the plug-in return the ID of the new layer, if it created one.

  UI:
    megawidgets are insufficient.  (No way to integrate entry_scale
      with tooltips or option_menu). Replace them.

  necessary luxuries:
    Add radio buttons for edge wrapping options.

  nicities:
    Find why two undo steps are required to undo.
    Find a way to reduce the speckling.

  excess luxuries:
    Variable IOR information in some [alpha?] channel.

  for version 1.1:
    THIS PLUGIN NEEDS A PREVIEW THING!
    Reflections

  for version > 1.1:
    Diffraction or whatever that thing that makes rainbows is called.
    Lighting