From: Joe Van Dyk <joevandyk@...>
Date: 2005-06-22T06:15:41+09:00
Subject: Re: tk canvas question

On 6/21/05, Joe Van Dyk <joevandyk@gmail.com> wrote:
> On 6/21/05, Joe Van Dyk <joevandyk@gmail.com> wrote:
> > Hi,
> >
> > I'm drawing stuff on a TkCanvas.  Essentially, a bunch of shapes that
> > move around.  I need to keep track of where each shape has been, so I
> > can draw the shape's history if needed (a "slug track").
> >
> > So every time a shape move, I store its position.  When I want to view
> > a shape's history, I draw a line connecting each stored position.
> >
> > I'm currently drawing all of these lines directly on to the main canvas.
> >
> > The problem is when I want to hide the history lines.  There can be
> > 400 shapes, and each of them could have thousands of lines that detail
> > their previous history.  Going through and deleting all the TkcLines
> > is taking a very long time.
> >
> > Is there a way to "group" each shape's history lines and then be able
> > to give one command that shows and hides the lines in that group?
> >
> > Thanks,
> > Joe
> 
> 
> Aha.  I found something called TkcGroup.  I'm having difficulties
> figuring out how to remove and/or hide the canvas objects that are in
> each group though.

I found this code out there somewhere:

#!/usr/bin/env ruby

require "tk"

canvas = TkCanvas.new
grp = TkcGroup.new(canvas)
grp.add(TkcRectangle.new(canvas, '1c', '2c', '3c', '3c',
				 'outline' => 'black', 'fill' => 'blue'))
canvas.pack

canvas.bind 'Enter' do
  grp.configure 'fill', 'red'
end
canvas.bind 'Leave' do
  grp.configure 'fill', 'green'
end

Tk.mainloop


I think it's supposed to have the rectangle change colors when the
cursor enters and leaves the canvas.  But I don't see any color change
occuring.  Can someone confirm this for me please?