Copyright © 2007-2008 Diggory Hardy
License: GNU General Public License version 2 or later (see COPYING)

Todo plan:
* means done

GUI:
->  Basic OpenGL code to:
    ->* create orthographic projection
    ->* draw boxes
    ->  maybe more (text, textures, ...)
->  Windows with size & position
    ->  position from Gui
->  Widgets:
    ->* minimum size but expandable, auto-set
        ->  no ability to resize yet except from config files
    ->  scripted widgets
->  Text rendering
    -> text library?
->  Drag & drop
    ->  click/drag start triggers a callback on the widget
        ->  when button is released, callback:
            ->  finds release location
            ->  checks if this is a valid drop target
            ->  if so, acts on it



Notes:
Some unifications of the coordinate system are needed:
    By default OpenGL uses the bottom left as the origin, with the first (bottom-left most) pixel at 0,0.
    SDL's mouse events use the top left as the origin, with the first (top-left most) pixel at 1,1.
I decided, for the GUI, to use the top-left at the origin with the top-left most pixel at 0,0. For OpenGL, the projection can simply be modified to achieve this; for SDL's events 1 is subtracted from each coordinate when the event is recieved.