Newbie plotting question

[Square Avenue <dfinton d umn edu>]

I'm just learning GTK+ and I figured the best way to learn it was by the
"Trial by Fire": creating a simple widget.

Armed with nothing but the on-line GTK tutorial (somewhat out of date) and
the source code, I tried something that I thought would be relatively
simple: A modified Drawing Area widget where my program can write to, a
pixel at a time, in any color I want.

The documentaion told be to use a backup off-screen pixmap, but was rather
vague in how to go about doing this.  Also, when I do try to follow the
instructions, I get wacky run-time errors like "gc != NULL".

The question is, is there a program out there that effectively
demonstrates how to simply do gdk_draw_* routines on an on-screen widget?
I'm only aiming to be able to draw individual pixels at a time, but there
doesn't seem to be any obvious way of doing it.

Thanks for any help, and forgive me for my obvious newbie-ness.  :)

                                      - Dave

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  Name:  David Finton                  | "All free software is in Beta.  If
 Email:  dfinton@d.umn.edu             |  there is a free software package
   Web:  http://www.d.umn.edu/~dfinton |  bearing the version number 1.0 or
                                       |  greater, it is obsolete and must
                                       |  be replaced immediately by a
                                       |  newer, better Beta version."
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