When filling a circle of radius 2400 pixels in an 640x480 output window, drawing
that circle takes over a second, although only a pixelspace of 640x480 is being
filled.

Below is a python test case demonstrating this:

------------

#!/usr/bin/env python

import cairo
import gtk
from math import pi

from time import time

class MainWindow(gtk.Window):
	def __init__(self):
		gtk.Window.__init__(self)
		self.connect('destroy', lambda x: gtk.main_quit())
		self.set_default_size(640, 480)
		self.set_position(gtk.WIN_POS_CENTER)
		
		drawingarea = gtk.DrawingArea()
		self.add(drawingarea)
		drawingarea.connect('expose_event', self.expose)
		
		self.show_all()
		
	def expose(self, da, event):
		ctx = da.window.cairo_create()
		
		##################################
		# TEST CASE BEGIN
		##################################
		ctx.set_source_rgb(0, 0, 0)
		ctx.arc(240.0,240.0,4800.0,0,2*pi)
		ctx.fill()
		##################################
		# TEST CASE END
		##################################

def main():	
	mainwindow = MainWindow()
	gtk.main()

if __name__ == "__main__":
	main()