# L-7 MCS 275 Wed 30 Jan 2008 : multigon.py

from Tkinter import *
import math

class MultiGon():
   """
   GUI to draw a regular n-gon on canvas.
   """
   def __init__(self,wdw):
      "determines the layout of the GUI"
      wdw.title('regular n-gon')
      self.d = 400
      self.n = IntVar()
      self.sn = Scale(wdw,orient='horizontal',\
        from_=1,to=20,tickinterval=1,\
        length=self.d,variable=self.n,\
        command=self.DrawGon)
      self.sn.set(10)
      self.sn.grid(row=0,column=0)
      self.c = Canvas(wdw,width=self.d,\
        height=self.d,bg ='white')
      self.c.grid(row=1,column=0)

   def DrawGon(self,v):
      "Draws a regular n-gon"
      cx = self.d/2
      cy = self.d/2
      radius = 0.4*self.d
      self.c.delete(ALL)
      self.c.create_text(cx,cy,text=v,tags="text")
      n = int(v)
      L = []
      for i in range(0,n):
         vx = cx + radius*math.cos(2*i*math.pi/n)
         vy = cy + radius*math.sin(2*i*math.pi/n)
         self.c.create_oval(vx-6,vy-6,vx+6,vy+6,width=1,\
             outline='black',fill='SkyBlue2',tags="dot")
         L.append((vx,vy))
      for i in range(0,n-1):
         self.c.create_line(L[i][0],L[i][1],L[i+1][0],L[i+1][1],width=2)
      self.c.create_line(L[n-1][0],L[n-1][1],L[0][0],L[0][1],width=2)

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

if __name__ == "__main__": main()