gui api design 22.02.2007 -- thu

Tony Sidaway made a uniform gui, level-based proposal.  Here are some thought
about it.

When issuing a widget, it must be possible to make it live in its own top-level
window or in a sub-window of the current window.

When issuing a widget, it must be possible to have a blocking behaviour or not.
The non-blocking behaviour needs some kind of callbacks to be passed.

Does the underlying gui code has to be initialized for each widget-issuing
command or do we provide a 'gui-init' function ? Is it state-based or do we
pass arguments around ?