Canvas, Ellipses, and RGBA

I just have some gripes and problems with the canvas which I'd like to 
share, and hopefully somebody can help me with them:

1.) First of all, how the hell do I come up with  guint32 for the 
color_fill_rgba with the GnomeCanvasItem's - I currently use just 
'fill_color' but I really really want to use the alpha channels. I have a 
GnomeColorPicker, but thats gives me _4_ values in various forms, i.e. 
double, guint8, guint16, etc?) anyway, how do I combine values that I 
gain from the GnomeColorPicker into /ONE/ guint32 for one guint32 RGBA 
value. Havoc's book is not very helpful with this, since he directly 
writes the RGBA values - Also, it appears to be a 'hex' value (i.e. it's 
something like 0x32ab9FFF which I find weird for a guint32). Help!

2.) Why on earth to ellipses use bounding boxes? wouldn't it make /much/ 
more sense to provide radius, and then x and y coordinates for the center 
- Thats how I learned how circles to be drawn. This is relatively easy to 
change on my own (just needs a little bit of math), so I don't really mind. 
But its just a nagging thing that I have. Also, when i do a 
gnome_canvas_item_move on an ellipse, what exactly gets moved, the 
center of the circle? the top-left corner of the boundin box? the center 
of the bounding box?

any help/info is appreciated :)

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