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From: dtj@caffeine.cray.com (Dean Johnson)
Newsgroups: comp.windows.x
Subject: Re: Controlling Viewport scrollbars.
Message-ID: <7323@caffeine.cray.com>
Date: 10 Jul 90 18:55:45 GMT
References: <roy.647556488@neptune>
Distribution: comp
Organization: Cray Research Inc. - Mendota Heights, Minnesota
Lines: 47

#include <std/disclaimers.h>

In article <roy.647556488@neptune> roy@neptune.iex.com (Roy Cantu) writes:
>
> The Viewport widget provides horizontal and vertical scrollbars to 
> control its child.  I was wondering how the application may gain
> control over these scrollbars.  Looking at the Scrollbar widget, I see 
> that the user may set the callback function, specify the thumb position, 
> specify the length of the thump etc.  
>
> Is it possible to gain such control over my Viewport scrollbars without 
> the hassle of implementing individual Scrollbar widgets?
>
> In particular, I would like to be notified when the user has moved 
> a scrollbar thumb and by how much.  Furthermore, I would like
> to be able to move the thumb and scroll the Viewport text from *within* 
> the application.
>   
>Any suggestions are appreciated.

Here is an example of how to move a viewport vertical scrollbar to the
top. Please note that there is probably no *correct* way to do this,
so be warned that children should use this only under parental supervision. 
(flames, etc. >& /dev/null)

	-Dean Johnson
	 Tools, Libraries, and Commands Group
	 Cray Research Inc.
	 Mendota Heights, MN

-------	cut here ---------

ZeroViewportScroll(widget)
ViewportWidget  widget;
{
Widget  v_bar;

        /*
         *      It doesn't make any sense to zero a viewport that doesn't
         *      currently exist.
         */
        if (!XtIsRealized((Widget) widget)) return;

        v_bar = XtNameToWidget(widget,"vertical");
        XtMoveWidget(widget->viewport.child,0,0);
        XtScrollBarSetThumb(v_bar,0.0,-1.0);
}