Demo/tkinter/matt/canvas-gridding.py

from Tkinter import *

# this is the same as simple-demo-1.py, but uses 
# subclassing. 
# note that there is no explicit call to start Tk. 
# Tkinter is smart enough to start the system if it's not already going. 

class Test(Frame):
    def printit(self):
	print "hi"

    def createWidgets(self):
	self.QUIT = Button(self, {'text': 'QUIT', 
				  'bg': 'red', 
				  'fg': 'white', 
				  'height' : 3, 
				  'command': self.quit})
	self.QUIT.pack({'side': 'bottom', 'fill': 'both'})	

	self.canvasObject = Canvas(self, {"width" : "5i", "height" : "5i"})
	self.canvasObject.pack({'side': 'left'})

    def mouseDown(self, event):
	# canvas x and y take the screen coords from the event and translate
	# them into the coordinate system of the canvas object
	self.startx = self.canvasObject.canvasx(event.x, self.griddingSize)
	self.starty = self.canvasObject.canvasy(event.y, self.griddingSize)

    def mouseMotion(self, event):
	# canvas x and y take the screen coords from the event and translate
	# them into the coordinate system of the canvas object
	x = self.canvasObject.canvasx(event.x, self.griddingsize)
	y = self.canvasObject.canvasy(event.y, self.griddingsize)

	if (self.startx != event.x)  and (self.starty != event.y) : 
	    self.canvasObject.delete(self.rubberbandBox)
	    self.rubberbandBox = self.canvasObject.create_rectangle(self.startx, self.starty, x, y)
	    # this flushes the output, making sure that 
	    # the rectangle makes it to the screen 
	    # before the next event is handled
	    self.update_idletasks()

    def __init__(self, master=None):
	Frame.__init__(self, master)
	Pack.config(self)
	self.createWidgets()

	# this is a "tagOrId" for the rectangle we draw on the canvas
	self.rubberbandBox = None

	# this is the size of the gridding squares
	self.griddingSize = 50

	Widget.bind(self.canvasObject, "<Button-1>", self.mouseDown)
	Widget.bind(self.canvasObject, "<Button1-Motion>", self.mouseMotion)
	

test = Test()

test.mainloop()