From: Hidetoshi NAGAI <nagai@...>
Date: 2008-01-10T00:13:20+09:00
Subject: Re: Ruby/Tk - binding to canvas items

From: Witold Rugowski <rugowski@nhw.pl>
Subject: Ruby/Tk - binding to canvas items
Date: Wed, 9 Jan 2008 06:38:33 +0900
Message-ID: <31383eb79838802c2314f99d24282680@ruby-forum.com>
> I have bunch of lines in one canvas. Event passed to code does refers
> only to widget which was clicked, but this is canvas itself, not
> particular canvas item. Is possible to know which line was clicked?

On Tcl/Tk's canvas manual, 
--------------------------------------------------------------------
   The tag current is managed automatically by Tk; it applies
   to the current item, which is the topmost item whose drawn
   area  covers  the  position  of  the mouse cursor.  If the
   mouse is not in the canvas widget or is not over an  item,
   then no item has the current tag.
--------------------------------------------------------------------
So, you should use 'current' to denote the target item.
Or use a TkcTagCurrent object.

For example, 
--------------------------------------------------------------------
require 'tk'
c = TkCanvas.new.pack
current = TkcTagCurrent.new(c)
callback = proc{|w|
  p c
  p w
  p w.itemconfiginfo('current')
  p current.configinfo
  p w.find_withtag('current')
}

[100, 120, 140, 160, 180, 200].each{|y|
  TkcLine.new(c, [50, y], [200, y]).bind('1', callback, '%W')
                              # or .bind('1', '%W', &callback)
}
Tk.mainloop
--------------------------------------------------------------------
-- 
Hidetoshi NAGAI (nagai@ai.kyutech.ac.jp)