# L-32 MCS 260 Fri 9 Nov 2007 : movedot.py
#
# GUI for a random walk.

from Tkinter import *
import random

class MovingDot():
   """
   GUI to illustrate an animation.
   """
   def __init__(self,wdw):
      "determines the layout of the GUI"
      wdw.title('a moving dot')
      self.d = 400
      self.c = Canvas(wdw,width=self.d,\
        height=self.d,bg ='white')
      self.c.grid(row=0,column=0,columnspan=2)
      self.T = Label(wdw,text="sleep time")
      self.T.grid(row=1,column=0,columnspan=2)
      self.x = self.d/2
      self.y = self.d/2
      self.go = False
      self.sleep = IntVar()
      self.step = IntVar()
      self.s = Scale(wdw,\
        orient='horizontal',from_=0,to=300,\
        tickinterval=50,resolution=1,\
        length=300,variable=self.sleep)
      self.s.grid(row=2,column=0,columnspan=2,\
         sticky=W+E+N+S)
      self.s.set(100)
      self.h = Scale(wdw,\
        orient='vertical',from_=0,to=100,\
        tickinterval=10,resolution=1,\
        length=400,variable=self.step)
      self.h.grid(row=0,column=2)
      self.h.set(10)
      self.b0 = Button(wdw,text="start",\
         command = self.start)
      self.b0.grid(row=3,column=0,sticky=W+E)
      self.b1 = Button(wdw,text="stop",\
         command = self.stop)
      self.b1.grid(row=3,column=1,sticky=W+E)

   def animate(self):
      "performs the animation"
      vx = self.x
      vy = self.y
      while self.go:
         self.c.delete("dot")
         self.c.create_oval(vx-6,vy-6,vx+6,vy+6,width=1,\
            outline='black',fill='SkyBlue2',tags="dot")
         n = self.step.get()
         vx = vx + random.randint(-n,n); 
         vy = vy + random.randint(-n,n)
         if vx >= self.d: vx = vx - self.d
         if vy >= self.d: vy = vy - self.d
         if vx < 0: vx = vx + self.d
         if vy < 0: vy = vy + self.d
         self.c.after(self.sleep.get())
         self.c.update()

   def start(self):
      "starts the animation"
      self.go = True
      self.animate()

   def stop(self):
      "stops the animation"
      self.go = False

def main():
   top = Tk()
   show = MovingDot(top)
   top.mainloop()

if __name__ == "__main__": main()