# Copyright (c) 1996 CNRI.

# Not quite as smooth as the Java version, but much smaller...
# (And with rivet, it has adequate speed!)

from Tkinter import *
import string
from whrandom import random

class Starfield:

    def __init__(self, master, width=400, height=100, numstars=50):
	self.width = width
	self.height = height
	self.canvas = Canvas(master, width=width, height=height,
			     background='black')
	self.canvas.pack()
	self.stars = []
	for i in range(numstars):
	    x = int(random()*width)
	    y = int(random()*height)
	    z = 1 + int(random()*10)
	    c = 35 + z*20
	    color = "#%02x%02x%02x" % (c, c, c)
	    tag = self.canvas.create_oval(x, y, x+4, y+4, fill=color)
	    self.stars.append((tag, z, [x]))
	self.update()

    def update(self):
	# Hack to test if we still exist
	try: self.canvas['width']
	except: return
	# Keeping track of x this way is much faster than bbox...
	for tag, z, xlist in self.stars:
	    x = xlist[0]
	    self.canvas.move(tag, z, 0)
	    x = x + z
	    if x > self.width:
		self.canvas.move(tag, -self.width, 0)
		x = x - self.width
	    xlist[0] = x
	self.canvas.after(10, self.update)
	    

if __name__ == '__main__':		# For stand-alone usage
    root = Tk()
    starfield = Starfield(root)
    root.mainloop()