GdkPixbuf rendering to partially obscured window

[Carl Nygard <cjnygard fast net>]

I have a GdkPixbuf rendering to a drawing area, and when the area is
obscured under another window, the bit under the window never gets the
image.  I'm drawing vectors to the same window at the same time, and
they get displayed via backing store just fine.

More clearly:

using drawing area obscured partially by gnome-terminal:
draw vectors to window
draw GdkPixbuf to window
remove gnome-terminal
result: no expose event because of backing store
        vectors are displayed via the backing store
        no raster displayed where terminal was

See the following images for clarification:
http://www.3sinc.com/gdkpixbuf/obscured-raster.png
http://www.3sinc.com/gdkpixbuf/missing-raster.png

Is this a problem with GdkPixbuf not rendering to what it knows is
obscured portions of the window?  Or is this a problem with SaveUnder or
BackingStore?

-- 
Carl Nygard <cjnygard fast net>