From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2003-05-29T17:19:32+09:00
Subject: Re: drawing on a scrolled (Tk)canvas

In article <bb37fa02f1l@enews3.newsguy.com>,
Phil Tomson <ptkwt@shell1.aracnet.com> wrote:
>It seems that after a TkCanvas has been scrolled, there is a mismatch 
>between coordinate values reported after a left-click on the canvas and 
>where items have actually been drawn on the canvas.  
>
>I'm trying to scroll a canvas and have the ability to draw a 'cursor' on 
>the canvas at the location of a left mouse click, but what I find is that 
>there is a mismatch between where the cursor is drawn and where the mouse 
>is clicked if the canvas has been scrolled.  Can someone explain what 
>happens to the coordinate system of a canvas after a scroll?
>


I found the answer: use the canvasx and canvasy functions like:

@canvas.bind('1',proc{|e| @manager.update_cursors(@canvas.canvasx(e.x)) })

seems to do the trick.

Phil