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From: Peter_King@NeXT.COM (Peter King)
Newsgroups: comp.sys.next
Subject: Re: View invalidation, scaling, [window display] vs. [view display]
Message-ID: <839@rosie.NeXT.COM>
Date: 29 May 91 01:18:55 GMT
References: <1991May20.163623.10272@engage.pko.dec.com>
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In article <1991May20.163623.10272@engage.pko.dec.com> tenny@ootool.dec.com  
(Dave Tenny) writes:
> 
> When I scale the docview in response to hitting a "magnify" button, say:
> 
> [docview scale :1.2 :1.2] ; 
> 
> then
> 
> [docview display] ;
> 
> the OLD contents of the docview are displayed, unscaled, as well as the 
> new, scaled contents.
> 
> However, if I do a
> 
> [window display] instead for the app's main window (which contains the 
> scrollview/docview), then everything works fine. However, this visibly
> redraws the whole window, and is unpleasant to watch.  
> 
> What is the proper way to redraw the docview?  
> 

I have two answers to your one question.

The best way to redraw a View that has invalidated what has already been drawn  
is to send it a "drawFromOpaqueAncestor:::" message.  You can use this snippit  
of code:

    [myView displayFromOpaqueAncestor:(NXRect *)0 :0 :NO];

Each View keeps track of whether it is opaque or not (the default).  To  
effectively erase parts of a View, its closest opaque ancestor needs to be  
redrawn.

The best way to magnify something in a ScrollView is to scale:: its contentView  
rather than its docView.  The contentView is almost always a member of the  
ClipView class.  Check out the documentation.  When you scale:: a ClipView, it  
will automatically redraw the docView *and* update the Scrollers to reflect the  
new size.

Peter

----------Disclaimers?  Always.  Everything's Subjective----------
Peter F. King	Developer Trainer	NeXT Computer, Inc.
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