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From: oster@dewey.soe.berkeley.edu (David Phillip Oster)
Newsgroups: comp.sys.mac.programmer
Subject: Re: ROM Unlocks handles (was Re: How to Argue Technical Points)
Message-ID: <33034@ucbvax.BERKELEY.EDU>
Date: 6 Dec 89 05:04:51 GMT
References: <2744@dogie.macc.wisc.edu> <3838@atr-la.atr.co.jp> <32977@ucbvax.BERKELEY.EDU> <3842@atr-la.atr.co.jp>
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Reply-To: oster@dewey.soe.berkeley.edu.UUCP (David Phillip Oster)
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In article <3842@atr-la.atr.co.jp> alain@atr-la.atr.co.jp (Alain de Cheveigne) writes:
>But hassle it is.  Is there a better way ?

Yes.  What complexity, and slowness! (all those unnecessary MovHHi()s can
really slow a program down.)  I too use very similar data structrues:
handles in the RefCons of my windows that themselves reference other
handles.

If a field referenced by an O.S. call is small, copy it. If it is large,
lock the owning handle during the call.  Do not write your own routines to
take pointers into handles, instead, if you must do such a thing, do it by
passing a handle an an offset. (Often you can just pass the handle, since
the routine knows its offset.)

Here is an example, from a program that uses a window handle which
references two pixmaps. (I keep the current window handle in a global
variable called "theDoc", by analogy with "thePort".) Notice, no need for
any HLocks or MoveHHis.

/* DocDispose - discard our window
 */
DocDispose(){
	if(NIL != (**theDoc).newPix){
		if(NIL != (**(**theDoc).newPix).baseAddr){
			DisposPtr((**(**theDoc).newPix).baseAddr);
			(**(**theDoc).newPix).baseAddr = NIL;
		}
		DisposPixMap((**theDoc).newPix);
	}
	if(NIL != (**theDoc).oldPix){
		if(NIL != (**(**theDoc).oldPix).baseAddr){
			DisposPtr((**(**theDoc).oldPix).baseAddr);
			(**(**theDoc).oldPix).baseAddr = NIL;
		}
		DisposPixMap((**theDoc).oldPix);
	}
	DisposHandle((Handle) theDoc);
	DisposeWindow(thePort);
}

Actually, this does bring up a question. Inside Mac Vol 5 doesn't say
precisely which fields are disposed when you call DisposPixMap().
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