[Tutor] tkinter canvas

[Mr Gerard Kelly]

wow, that's excellent, thanks so much.

I haven't got a clue how lambda functions work, but they seem pretty
useful, so I'll try to figure them out.

----- Original Message -----
From: Kent Johnson <kent37 at tds.net>
Date: Thursday, January 15, 2009 10:24 pm
Subject: Re: [Tutor] tkinter canvas
> On Thu, Jan 15, 2009 at 12:41 AM, Mr Gerard Kelly
> <s4027340 at student.uq.edu.au> wrote:
> 
> > I want to be able to bind these boxes to an event - so that I can 
> either> click on them, or hold the mouse cursor over them, and have 
> them change
> > color.
> 
> Here is a version of your program that binds the Enter and Leave
> events to each box and changes the box color when the mouse is over
> it:
> 
> #########################
> 
> from Tkinter import *
> 
> master = Tk()
> 
> numboxes=6
> 
> width=40*(numboxes+2)
> height=200
> w = Canvas(master, width=width, height=height)
> w.pack()
> 
> size=width/(numboxes+2)
> 
> box=[0]*numboxes
> 
> def enter(e, i):
>    e.widget.itemconfigure(box[i], fill='red')
> 
> def leave(e, i):
>    e.widget.itemconfigure(box[i], fill='blue')
> 
> for i in range(numboxes):
>    box[i]=w.create_rectangle((1+i)*40, 40, (2+i)*40, height-40, 
> fill="blue")    w.tag_bind(box[i], '<Enter>', lambda e, i=i: 
> enter(e, i))
>    w.tag_bind(box[i], '<Leave>', lambda e, i=i: leave(e, i))
> 
> mainloop()
> 
> #######################
> 
> The 'i=i' in the lambda is needed due to the (surprising) way that
> variables are bound to closures; without it, every event would be
> bound to the same value of i. Some explanation here:
> http://code.activestate.com/recipes/502271/
> 
> Kent
>