use of GdkBitmap in gtk_widget_shape_combine_mask()

["Stéphane Charette" <stephanecharette gmail com>]

Disclaimer:  I'm very new to Gdk, Gtk, and X.

In gtk_widget_shape_combine_mask(), I need to pass in a GdkBitmap to
use as the mask.  All of the examples I've found create the
GdkBitmap/GdkPixmap from static XPM or XBM data.

Question #1:
How do I create a GdkBitmap dynamically at runtime?  That is, not from XPM/XBM?

Question #2:
To be even more specific, can I create a GdkBitmap from what I get
using Cairo?  For example, can I call cairo_arc() or cairo_rectangle()
to do some drawing for me into <something> that results in me having a
GdkBitmap?

Thanks!

Stéphane Charette