[cairo] SVG Spacewar

[Nigel Tao]

Hello all.  I've been playing around with Cairo lately, and have made a
little re-make of the classic Spacewar game, but with SVG-like graphics.
It's more of a proof-of-concept at this stage than a full-fledged game,
but I think that it's quite playable.

I put up a home page at the only publicly available web space that I
currently have (under the sourceforge page of another project of mine):
http://browserbookapp.sourceforge.net/svgspacewar/
but I would love to see this live in the cairo-demo module in CVS, if
the powers that be are happy with that (it's pretty small, just 1100
lines of C and a Makefile).  Otherwise, I'll get around to setting up a
new SF project.

Feedback most welcome.  This is my first venture with Cairo, and I am
not 100% confident with C either, so I might be making simple mistakes.

In particular, like all game programmers, I would like it to run as fast
as possible, and that means employing glitz.  But how do I know if I'm
running glitz (I downloaded the snapshot and I think it's installed, but
my CPU seems to be rather busy)?  If I'm not, how do I switch to glitz?
If it matters, I am running Fedora Core 3 with nVidia binary drivers.

But also, scaling the whole thing by a small-ish factor (x1.25, try
pressing "[" or "]" when playing) or enlarging the app's window seems to
bring it to its knees (100% CPU use, and "top" just reports the culprit
as 99% "X") - certainly it doesn't seem like an O(N^2) kind of thing.
Any hints on how to profile, or what I'm doing wrong?

Animation is done using gtkcairo, and I have just done the simplest
thing (like the sproing demo) and set up a g_timeout_add to
gtk_widget_queue_draw every 25ms - but is there a better way?  One that
will allow higher (or maximum?) frame rates, and without artifacts like
shearing?


Source code released under the GPL.  Built against the cairo 0.4.0
snapshot.

tia,
Nigel.