Graphing widget (oscilloscope-like)?

[david hagood gmail com]

Disclaimer: I am new to GTK programming.

I'm looking for a widget which can display an oscilloscope-like display:
that is, a drawable surface with an overlaid graticule of horizontal and
vertical lines, plus zero or more traces consisting of a set of connected
line segments defined by an array of (x,y) pairs. Ideally other "things"
should be drawable to the surface (e.g. limit lines, markers, annotating
text, filled polygons (limit masks)).

The GTK "curve" object looks pretty close to what I need, but it is marked
as deprecated.

(I'm about to use bad language here, be forewarned): the license is
important, as this will be going into code that is, unfortunately,
proprietary - as such GPL is out, but LGPL is acceptable.

It seems to me that a graphing widget (which is really what I need) ought
to be something of common enough interest to be available, but I've not
been able to find one.

Failing the availability of such a beast, I'll have to write one (which I
would try to get licensed under LGPL - I don't think my bosses would have
a problem with that). If that happens, does anybody have any good pointers
for writing an efficient line-drawing widget (e.g. should I draw the
graticule once to an offscreen bitmap and then blit that to the drawable
when I refresh, or would it be faster to keep the graticule as a set of
pre-defined line segments and just redraw them each refresh)? Does anybody
else have need for such a thing and suggestions on what they'd like to
see?