# file: slide.py
#
# author: Bob Muller
# date: October 28, 2007
#
# This file contains python code using the turtle graphics system.
# The code in this file, slides a box across the x-axis. There are two
# versions, one using a while-loop and one using recursion.
#
import turtle

def setup(h,w):
    turtle.setup(height = h, width = w)
    turtle.degrees()
    turtle.up()

# box is a helper function that simply draws a square box of a specified
# color. NB: the pen is up(!) because things are too slow when the pen is
# down.
#
def box(x,y,side,color):

    turtle.color(color)
    turtle.goto(x,y)
    turtle.begin_fill()

    turtle.goto(x+side,y)
    turtle.goto(x+side,y+side)
    turtle.goto(x,y+side)
    turtle.goto(x,y)

    turtle.end_fill()

# slide1 slides a square box across the x-axis (y == 0) of the turtle
# graphics window.
#
def slide1(side, color, delta):

    x = - (turtle.window_width() / 2.0)
        
    while x < (turtle.window_width() / 2.0) - side:

        box(x, 0, side, color)
        box(x, 0, side, 'White')

        x = x + delta

# slide2 slides a square box across the x-axis (y == 0) of the turtle
# graphics display. slide2 uses recursion to effect repetition.
#
def slide2(side,color,delta):
    slide2Help(-(turtle.window_width() / 2.0), side, color, delta)

def slide2Help(x,side,color,delta):

    box(x, 0, side, color)
    
    if x < turtle.window_width() / 2.0:
        
        box(x, 0, side, 'White')

        slide2Help(x + delta, side, color, delta)