drawing pictures

[Stefan Ottosson <ottosson canit se>]

I want to show a .png image in a window using gdk/gtk.
I have decoded the .png image, and so I have a buffer 
containing RGB data.
So what do I do to display it? Would it be enough to 
call gdk_pixmap_create_from_data(..) with the data
argument pointing to my RGB buffer, and then drawing
the resulting pixmap in my expose event handler? 
Or do I have to mess with colormaps and stuff too?
I have no experience of xlib programming so this isnt
obvious to me..