From: Morton Goldberg <m_goldberg@...>
Date: 2006-09-28T02:18:11+09:00
Subject: Re: Feedback messages to user using Tk...

On Sep 27, 2006, at 10:57 AM, Cameron, Gemma (UK) wrote:

> 6. Now call Tk.mainloop
>
> ^^ I think maybe that's where I was going wrong. I wrote a unit  
> test to
> test the updating of the label. My code looked something like this:
>
> class GraphicalProgress
>   def initialize
>     root = TkRoot.new { title 'Progress' }
>     @my_label = tkLabel.new(root)
>     @my_label.configure('text'=>'Waiting for something to report...')
>     @my_label.pack
>
>     Tk.mainloop
>   end
>
>   def update(message)
>     @my_label.configure('text'=>'Waiting for something to report...')
>   end
> end
>
> Unit Test:
>
> @progress = GraphicalProgress.new
> @progress.update('I'm doing something')
> @progress.update('I'm done')
>
> And because the loop is in the initialize method, only when the app is
> closed do we get to the line which requests the text is update. Of
> course this falls over as the widget has been destroyed...
>
> So with your suggestion the code should be something like this...
>
> class GraphicalProgress
>   def initialize
>     root = TkRoot.new { title 'Progress' }
>     @my_label = tkLabel.new(root)
>     @my_label.configure('text'=>'Waiting for something to report...')
>     @my_label.pack
>   end
>
>   def update(message)
>     @my_label.configure('text'=>'Waiting for something to report...')
>   end
> end
>
> Unit Test:
>
> @progress = GraphicalProgress.new
> @progress.update('I'm doing something')
> @progress.update('I'm done')
> Tk.mainloop
>
> Or have I got the wrong end of the stick?
>
> Thanks so much for your help!

There are quite a few errors in that code. Even if you fixed its  
syntax, you'd have a conceptual error. You'd only see the last  
message: "I'm done". The initial message would be replaced by the  
first update call and the second message would then be replaced by  
the second update call before the window got on the screen. But  
you're moving in the right direction.

You need something to delay the updates until the window gets  
displayed. A timer is one way to do it.

<code>
#! /usr/bin/ruby -w

require 'tk'

class GraphicalProgress
    def initialize
       root = TkRoot.new { title 'Progress' }
       @my_label = TkLabel.new(root) {
          text 'Waiting for something to report...'
       }
       @my_label.pack(:pady=>20)
       # Set initial window geometry; i.e., size and placement.
       win_w, win_h = 300, 80
       # root.minsize(win_w, win_h)
       win_x = (root.winfo_screenwidth - win_w) / 2
       root.geometry("#{win_w}x#{win_h}+#{win_x}+50")
       root.resizable(false, false)
    end

    def update(message)
       @my_label.text = message
    end
end

msgs = ["I'm doing something", "I'm done"]
indx = 0
progress = GraphicalProgress.new
timer = TkTimer.start(1000, 2) do
    progress.update(msgs[indx])
    indx += 1
end

Tk.mainloop
</code>

Regards, Morton