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From: lippin@skippy (tom lippincott)
Newsgroups: comp.sys.mac
Subject: Re: What does access memory manager' mean?
Message-ID: <1329@cartan.Berkeley.EDU>
Date: Thu, 15-Oct-87 04:37:10 EDT
Article-I.D.: cartan.1329
Posted: Thu Oct 15 04:37:10 1987
Date-Received: Sat, 17-Oct-87 05:45:47 EDT
References: <5365@jade.BERKELEY.EDU> <10620001@hpfclm.HP.COM> <1319@cartan.Berkeley.EDU> <6471@apple.UUCP>
Sender: nobody@cartan.Berkeley.EDU
Reply-To: lippin@skippy.UUCP (tom lippincott, ..ucbvax!bosco!lippin)
Organization: UC Berkeley Math Department
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Recently tecot@apple.UUCP (Ed Tecot) said:
>In summary, QuickDraw is reentrant, but it's dependency upon the memory
>manager precludes its use during interrupt time.
>						_emt


Where were you a few months ago when I needed to make use of this?
I was only writing a prototype of a program, and I figured that
locking down everything in sight and trying this would be safe enough
for my purposes.

I had a VBL task doing some drawing; I wanted characters, but would
settle for lines, or a copybits call.  Meanwhile, the main program
wanted to draw sometimes.  What happens?  Whenever the main program
is interrupted while drawing over the cursor, it leaves a cursor image
lying on the screen.  Fine for drawing pine forests, but not good for much
else.

I eventually tracked this down to the QD cursor globals getting confused,
and had the VBL task save and restore them as necessary.  Another
not-so-good step, but it certainly looks like the calls were *not*
reentrant.  I hope you're not speaking for Apple on this one.

Sorry if I sound a little harsh, but it's just not so.

					--Tom Lippincott
					..ucbvax!bosco!lippin

"If it was so, then it would be, and if it were so, then it could be,
	but as it isn't, it ain't.  That's Logic."  --Tweedledee