#(c) Rory Clune 02/13/2011
# A Bouncing Ball, using python's tkinter library

from Tkinter import *
from numpy import*
import time

def drawball (cv,x,y,radius):
    return cv.create_oval(x+radius, y+radius, x-radius, y-radius, fill='white')

def paint(parent,cv):
    global ball, pos, vel, rad, cr, width, height, dt, g
    #update the y-component of velocity under gravity
    oldX, oldY = pos[0], pos[1]
    vel[1] +=g*(dt*1000)    
    #update the ball's position:
    pos[0]+=vel[0]*(dt*1000)
    pos[1]+=vel[1]*dt*1000 + 0.5*g*(dt*1000)*(dt*1000)
    #check for collision with walls 
    if pos[0]-rad< 0: vel[0] = -vel[0]*cr; vel[1]*=fr; pos[0] = rad
    elif pos[0]+rad> width: vel[0] = -vel[0]*cr; vel[1]*=fr; pos[0] = width - rad        
    if pos[1]-rad < 0: vel[1] = -vel[1]*cr; vel[0]*=fr; pos[1] = rad        
    elif pos[1]+rad > height: vel[1] = -vel[1]*cr; vel[0]*=fr; pos[1] = height - rad
    # move the ball
    cv.move(ball, pos[0]-oldX, pos[1]-oldY)
    time.sleep(dt)
    parent.after_idle(paint,parent,cv)

#create the "root":
root = Tk()
root.title("A bouncing ball using tkinter")
root.bind('q','exit')
# create the drawing canvas and "pack" it
width, height = 500, 500
cv = Canvas(root, width=500, height=500, bg='grey')
cv.pack()
pos = [200, 100]#initial position
vel = [3,0]#initial velocity
cr,fr, g = 0.8,0.95,0.002#coefficients of restitution and friction, and gravity
rad = 25#radius of the ball
dt = 0.004#timestep
ball = drawball(cv,pos[0],pos[1],rad)
#delay the first call to paint by 100ms
root.after(100,paint,root,cv)    
root.mainloop()