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From: d88-jwa@byse.nada.kth.se (Jon W{tte)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Question: scrolling in a window
Message-ID: <D88-JWA.91Mar16160052@byse.nada.kth.se>
Date: 16 Mar 91 15:00:45 GMT
References: <1991Mar14.021122.292@husc3.harvard.edu>
	<1991Mar15.032155.305@husc3.harvard.edu>
Sender: news@nada.kth.se (Mr News)
Organization: Royal Institute of Technology, Stockholm, Sweden
Lines: 44
In-reply-to: reiss@husc9.harvard.edu's message of 15 Mar 91 08:21:54 GMT


In article <> reiss@husc9.harvard.edu (Peter Reiss) writes:

   works, but does not look very good.  I have noticed that most programs
   seem to scroll graphics by shifting the current picture in one
   direction and drawing in the extra area.  How can I do this?

ScrollRect() - it also accumulates a region in a RegionHandle
which needs to be repainted.

Like this:

void
ScrollUpDown ( int amount )
{
	RgnHandle saveClip , updateClip ;
	Rect r ;

	r = thePort -> portRect ;
	updateClip = NewRgn ( ) ;
	saveClip = NewRgn ( ) ;
	if ( ! saveClip ) {
		DoSysErr ( MemError ( ) ) ;
	}

	ScrollRect ( & r , 0 , amount , updateClip ) ;

	/* Update variables according to scroll */

	GetClip ( saveClip ) ;
	SetClip ( updateClip ) ;

	DrawEverything ( ) ;

	SetClip ( saveClip ) ;

	DisposeRgn ( saveClip ) ;
	DisposeRgn ( updateClip ) ;
}

--
"The IM-IV file manager chapter documents zillions of calls, all of which
seem to do almost the same thing and none of which seem to do what I want
them to do."  --  Juri Munkki in comp.sys.mac.programmer