Getting the mask out of a pixmap

[katre <katre ruf rice edu>]

All right.  After many months of coding, getting frustrated, and asking stupid
questions here, I'm getting near the end.  I've figured out how to use a
bitmapped mask of a pixmap to fake transparency.  Now the question is, how do
I get the mask of a pixmap?  My pixmap is allocated as the same size as the
widget, same depth, etc, and I've been giving it a background color just so
that when I look at it, it makes sense.  However, when I try using
gdk_draw_pixmap (mask, gc, pixmap, 0, 0, width, height), I get a nasty looking
error message, with a bunch of numbers tacked onto the end.  In fact, i get
this message any time I try using a GdkBitmap as a GdkDrawable in a gdk_draw
function.  So, what am I doing wrong, and how do I fix it?

katre