From: Joe Van Dyk <joevandyk@...>
Date: 2005-06-22T06:19:47+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:
> > 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?
> 

Here's the link to the original tk code, and the corresponding Ruby code.

http://www2s.biglobe.ne.jp/~Nori/ruby/ja/tk-ref/itemconfigure.html

The Tk code works for me, while the Ruby one doesn't.