From: Morton Goldberg <m_goldberg@...>
Date: 2006-09-27T20:53:19+09:00
Subject: Re: Feedback messages to user using Tk...


On Sep 27, 2006, at 4:26 AM, Cameron, Gemma (UK) wrote:

>
> Hi all!
>
> If anyone is very familiar with Tk I would be very grateful for a  
> few pointers.
>
> Basically I'm looking to feedback my program's output to the user  
> in a GUI (Tk Label) rather than printing to the console (which it  
> currently does). This information would simply be a string to let  
> the user know what's going on and maybe even what percentage of the  
> work has been done. I don't want a command/bound event to drive  
> this - I simply want to send a message to a method which will  
> update the Tk Label dynamically.
>
> I envision the calling the class like this:
>
>     @output = GraphicalOutput.new
>     @output.message("Now moving files....")
>
> to replace the current:
>     p "Now moving files..."
>
> Is this possible with Tk? I've been looking for days now and  
> haven't found much. I know how to use the TkLabel.configure 
> ('text'=>..) etc. to update the text, however just calling this  
> when the mainloop is running does not seem to dynamically update  
> the label. I've even got the stopwatch example going from the  
> O'Reilly cookbook.
>
> Am I using the wrong approach and/or mentality for this problem?!

Ruby/Tk makes it easy to do what you want. You don't need to bother  
with low-level methods like 'configure' -- Ruby/Tk provides more  
runbyish ways -- in this case access methods for a label's text. I  
hope the following small example will help you.

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

require 'tk'

DEBUG = []

MESSAGES = [
    "This is the first message",
    "This is another message",
    "This is the third message",
    "Are you getting bored?"
]

class TestWindow
    # Each time the button is clicked on, the label shows a new message.
    def btn_action
       @indx = (@indx + 1) % MESSAGES.length
       @lbl.text = MESSAGES[@indx]
    end

    def initialize
       begin
          @indx = 0

          # Set up the widgets.
          root = TkRoot.new { title 'Ruby Tk' }
          @lbl = TkLabel.new { text MESSAGES.first }
          @btn = TkButton.new { text "Next Message" }
          @btn.command = lambda { btn_action }
          @lbl.pack(:pady => 20)
          @btn.pack(:pady => 20)

          # Set initial window geometry; i.e., size and placement.
          win_w, win_h = 300, 135
          # root.minsize(win_w, win_h)
          win_x = (root.winfo_screenwidth - win_w) / 2
          root.geometry("#{win_w}x#{win_h}+#{win_x}+50")

          # Set resize permissions.
          root.resizable(false, false)

          # Make Cmnd+Q work as expected (running on OS X).
          root.bind('Command-q') {Tk.root.destroy}

          Tk.mainloop
       ensure
          puts DEBUG unless DEBUG.empty?
       end
    end
end

TestWindow.new
</code>

Regards, Morton