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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ames!oliveb!apple!applelink.apple.com!MAC.ROMOS
From: MAC.ROMOS@applelink.apple.com (Ian Hendry)
Newsgroups: comp.sys.mac.programmer,comp.sys.mac
Subject: Re: CopyBits in MPW C 3.0
Message-ID: <1458@internal.Apple.COM>
Date: 20 Apr 89 02:01:06 GMT
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References:<225@uw-apl.UUCP> <2403@helios.ee.lbl.gov>

In article <8904171804.AA00203@vs03csc.UMD.EDU> russotto@wam.UMD.EDU 
writes:
> I've never had any problem passing dereferenced handles to CopyBits--
> I don't believe it is a routine that moves or purges memory (I believe
> it's temp buffers are on the stack)  Actually, this almost has to be
> for VBL tasks to be able to draw...

WRONG!
Copybits generally does not affect memory, but in some cases it does!  DO 
NOT pass unlocked dereference handles!  There are cases where QD may make 
memory calls during copybits (which would screw up a dereferenced handle) 
and even if I didn't know actual cases I sure wouldn't count on being able 
to pass dereferenced handles and have future compatability!
For example the (very) newly announced 32-Bit extensions to color quckdraw 
have more such cases than the unextended color quickdraw versions, but 
even the older versions do have cases.

Sorry (but not too sorry) if the above is phrased strongly.   :-)

The point is that the cases exist and Apple has said this trap may move 
memory so this is definately a case in which you should follow Apple's 
guidelines.

Ian Hendry
MAC.ROMOS@applelink.apple.com
Make sure my name is in the subject of any Email, or post replies to 
network.
TE: 408-974-4737

Disclaimer:  It was all HIS idea anyway!  Nothing I say reflects anything 
my employer means... or anything I mean for that matter.