[plt-scheme] Continuous update sliders ...

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Fri Jul 4 08:19:42 EDT 2008

At Fri, 04 Jul 2008 11:23:45 +0800, kumar_lista at mac.com wrote:
> Hi,
> I need some help with the slider% class. Much appreciate any tips.
> The slider% class behaves modally as it stands - i.e. between mouse-down
> and mouse-up on the slider control, the main event loop does not get  
> to run.
> How do I configure slider% such that I can twiddle it without pausing  
> the
> main event loop between mouse-down and mouse-up?

Provide a `callback' argument when creating a `slider%'.

The following example illustrates updating a message field
interactively based on the value of the slider:

 #lang scheme/gui

 (define f (new frame% [label "Hi"]))
 (define m (new message% [parent f] [label ""] 
               [stretchable-width #t]))
 (new slider% 
      [label #f] [min-value 0] [max-value 100]
      [parent f]
      [callback (lambda (s e)
                  (send m set-label
                        (format "Value is ~s" (send s get-value))))])
 (send f show #t)

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