""" GDRAW Demonstration:  Bouncing Ball with User Controlled Paddle."""
## Use with command "python -i bounce.py", where this file is called bounce.py,
## OR try uncommenting the last line of this file.
## This code is a direct translation of the original STK (scheme) code.

## Copyright 2005 Boley

from gdraw import *
from gc import collect  ## this is optional

ball=fill_oval(110,110,120,120,'red')
box=draw_rectangle(100,100,400,400)
paddle=fill_rectangle(90,100,100,150,'black')
velocity=[7,11]
move_p=[False]

def center(coords):
    return [(coords[0]+coords[2])/2,(coords[1]+coords[3])/2]

def get_new_pos():     ## compute next ball position, checking for wall bounce
    old_pos=get_coords(ball)
    pos_paddle=get_coords(paddle)
    pos_box=get_coords(box)
    new_pos=[old_pos[0]+velocity[0], old_pos[1]+velocity[1],\
             old_pos[2]+velocity[0], old_pos[3]+velocity[1]]
    if new_pos[0]<pos_paddle[2]:  ## ball hits left wall (check for paddle)
        c=center(old_pos)
        if pos_paddle[1]<=c[1] and c[1]<=pos_paddle[3]:
            velocity[0]=-velocity[0]
	    collect()
        else:
            move_p[0]=False
            velocity[0]=abs(velocity[0])
            print "lost ball: stop.  Click again to resume."
    elif pos_box[2]<new_pos[2]:   ## ball hits right wall
        velocity[0]=-velocity[0]
	collect()
    elif new_pos[1]<pos_box[1]:   ## ball hits top wall
        velocity[1]=-velocity[1]
	collect()
    elif pos_box[3]<new_pos[3]:   ## ball hits bottom wall
        velocity[1]=-velocity[1]
	collect()
    new_pos=[old_pos[0]+velocity[0], old_pos[1]+velocity[1],\
             old_pos[2]+velocity[0], old_pos[3]+velocity[1]]
    return new_pos
     
def update_pos():      ## move the ball to the next computed position.
    if move_p[0]:
        new_pos=get_new_pos()
        if move_p[0]:
            def thunk():
                set_coords(ball,new_pos)
                update_pos()
            after(50,thunk)
    else:
        print "paused.  Click to resume."

def move_paddle(e):   ## paddle simply follows the mouse (vertical only)
    pos_paddle=get_coords(paddle)
    pos_box=get_coords(box)
    mouse=get_mouse_coords()
    if move_p[0] and pos_box[1]<mouse[1] and mouse[1]<pos_box[3]:
        set_coords(paddle,pos_paddle[0],mouse[1]-25,pos_paddle[2],mouse[1]+25)

set_motion_binding(0,move_paddle)

def go(e):
    move_p[0]=not move_p[0]
    if move_p[0]:
        print "go ..."
        update_pos()
    else: print "pause ..."

set_binding(0,go)
print "======= Click on the canvas.  Control paddle with mouse. Click again to pause."

# CanvasWindow.mainloop() # uncomment this line if running non-interactively,
                          # or on a non-unix computer.