drawing a png, honoring transparency

[Akos Maroy <darkeye tyrell hu>]

Hi,

I'm trying to draw a PNG image, which has some transparent parts, by 
calling Gdk::Pixbuf::render_to_drawable().

The documentation of this function says that this call will not honor 
transparency, or that's how I understand the following:


"Note that this function will ignore the opacity information for images 
with an alpha channel; the GC must already have the clipping mask set if 
you want transparent regions to show through."


now, how would I generate the clipping mask for a transparent PNG image? 
I see functions like Gdk::Pixbuf::render_pixmap_and_mask(), but I just 
don't know how to use them.. (and there's no documentation for them 
either :(


Akos