#! /usr/bin/env python

# Simulate "electrons" migrating across the screen.

# An optional bitmap file in can be in the background.

#

# Usage: electrons [n [bitmapfile]]

#

# n is the number of electrons to animate; default is 30.

#

# The bitmap file can be any X11 bitmap file (look in

# /usr/include/X11/bitmaps for samples); it is displayed as the

# background of the animation.  Default is no bitmap.

from Tkinter import *

import random

# The graphical interface

class Electrons:

    # Create our objects

    def __init__(self, n, bitmap = None):

        self.n = n

        self.tk = tk = Tk()

        self.canvas = c = Canvas(tk)

        c.pack()

        width, height = tk.getint(c['width']), tk.getint(c['height'])

        # Add background bitmap

        if bitmap:

            self.bitmap = c.create_bitmap(width/2, height/2,

                                          bitmap=bitmap,

                                          foreground='blue')

        self.pieces = []

        x1, y1, x2, y2 = 10,70,14,74

        for i in range(n):

            p = c.create_oval(x1, y1, x2, y2, fill='red')

            self.pieces.append(p)

            y1, y2 = y1 +2, y2 + 2

        self.tk.update()

    def random_move(self, n):

        c = self.canvas

        for p in self.pieces:

            x = random.choice(range(-2,4))

            y = random.choice(range(-3,4))

            c.move(p, x, y)

        self.tk.update()

    # Run -- allow 500 movemens

    def run(self):

        try:

            for i in range(500):

                self.random_move(self.n)

        except TclError:

            try:

                self.tk.destroy()

            except TclError:

                pass

# Main program

def main():

    import sys, string

    # First argument is number of electrons, default 30

    if sys.argv[1:]:

        n = string.atoi(sys.argv[1])

    else:

        n = 30

    # Second argument is bitmap file, default none

    if sys.argv[2:]:

        bitmap = sys.argv[2]

        # Reverse meaning of leading '@' compared to Tk

        if bitmap[0] == '@': bitmap = bitmap[1:]

        else: bitmap = '@' + bitmap

    else:

        bitmap = None

    # Create the graphical objects...

    h = Electrons(n, bitmap)

    # ...and run!

    h.run()

# Call main when run as script

if __name__ == '__main__':

    main()