[cairo] Why is my simple python gtk+cairo program running so slowly/stutteringly?

[Rye Terrell]

My program draws circles moving on the window. I think I must be missing
some basic gtk/cairo concept because it seems to be running too
slowly/stutteringly for what I am doing. Any ideas? Thanks for any help!


#!/usr/bin/env python

import gtk
import gtk.gdk as gdk
import math
import random
import gobject

# The number of circles and the window size.
num = 128
size = 512

# Initialize circle coordinates and velocities.
x = []
y = []
xv = []
yv = []
for i in range(num):
    x.append(random.randint(0, size))
    y.append(random.randint(0, size))
    xv.append(random.randint(-4, 4))
    yv.append(random.randint(-4, 4))


# Draw the circles and update their positions.
def expose(*args):
    cr = darea.window.cairo_create()
    cr.set_line_width(4)
    for i in range(num):
        cr.set_source_rgb(1, 0, 0)
        cr.arc(x[i], y[i], 8, 0, 2 * math.pi)
        cr.stroke_preserve()
        cr.set_source_rgb(1, 1, 1)
        cr.fill()
        x[i] += xv[i]
        y[i] += yv[i]
        if x[i] > size or x[i] < 0:
            xv[i] = -xv[i]
        if y[i] > size or y[i] < 0:
            yv[i] = -yv[i]


# Self-evident?
def timeout():
    darea.queue_draw()
    return True


# Initialize the window.
window = gtk.Window()
window.resize(size, size)
window.connect("destroy", gtk.main_quit)
darea = gtk.DrawingArea()
darea.connect("expose-event", expose)
window.add(darea)
window.show_all()


# Self-evident?
gobject.idle_add(timeout)
gtk.main()
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