# L-32 MCS 260 Fri 9 Nov 2007 : slidedot.py
#
# To get used to the screen coordinates,
# we slide a dot along the canvas.

from Tkinter import *

class SlideDot():
   """
   GUI to demonstrate canvas coordinates.
   """
   def __init__(self,wdw):
      "determines the layout of the GUI"
      wdw.title('sliding a dot')
      self.d = 400
      self.c = Canvas(wdw,width=self.d,\
        height=self.d,bg ='white')
      self.c.grid(row=1,column=0)
      self.x = IntVar()
      self.y = IntVar()
      self.L = 0; self.H = self.d
      self.sx = Scale(wdw,\
        orient='horizontal',\
        from_=self.L,to=self.H,\
        tickinterval=(self.H-self.L)/10,\
        resolution=(self.H-self.L)/100,\
        length=self.d,variable=self.x,\
        command=self.DrawCircle)
      self.sx.grid(row=0,column=0)
      self.sx.set(self.d/2)
      self.sy = Scale(wdw,\
        orient='vertical',\
        from_=self.L,to=self.H,\
        tickinterval=(self.H-self.L)/10,\
        resolution=(self.H-self.L)/100,\
        length=self.d,variable=self.y,\
        command=self.DrawCircle)
      self.sy.grid(row=1,column=1)
      self.sy.set(self.d/2)

   def DrawCircle(self,v):
      "draws the dot and its scale variable"
      vx = self.x.get()
      vy = self.y.get()
      self.c.delete("dot","text")
      t = '(' + str(int(vx)) + ',' + str(int(vy)) + ')'
      self.c.create_text(vx,vy-10,text=t,tags="text")
      self.c.create_oval(vx-6,vy-6,vx+6,vy+6,width=1,\
         outline='black',fill='SkyBlue2',tags="dot")

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

if __name__ == "__main__": main()