Novice canvas questions

[Arturo Tena <arturo directmail org>]

Hi!

I'm learning GnomeCanvas and friends, and I have some little questions:

1. When I create a new canvas, GGAD say one may could create it under a
non-default visual and colormap, in the following way (in GDK mode):

   GtkWidget* canvas;
   gtk_widget_push_visual(gdk_imlib_get_visual());
   gtk_widget_push_colormap(gdk_imlib_get_colormap());
   canvas = gnome_canvas_new();
   gtk_widget_pop_visual();
   gtk_widget_pop_colormap();

  My question is: why should I need a non-default visual and a colormap?
  (if anyone notice, this question is really: "what is a visual and a
   colormap?". If anybody knows a easy introduction abouty visual and
   colormaps, I will thank to point me to it.)

2. It seems to me that AA mode supports traslucent canvas items, but GDK
mode doesn't. Is that correct?

-- 
Arturo Tena
arturo@directmail.org