[gtkada] Delaying screen updates for drawing area

[Arnaud Charlet]

> I am in a windows system, double buffer demo crashes as soon as loaded, so i 
> cant do anything with it ?...

The double buffer demo has trouble on windows due to a particular use of tasks,
but this has nothing to do with double buffer per se.

You might want to take a look at a book on graphics to understand how one
does double buffering, since this is a standard technique which is not
specific to GtkAda.

Arno