Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Finding the size of the screen under Multifinder/Color QD
Message-ID: <9481@hoptoad.uucp>
Date: 3 Jan 90 23:43:18 GMT
References: <10139@saturn.ucsc.edu> <9429@hoptoad.uucp> <1102@urbana.mcd.mot.com>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 42

In article <10139@saturn.ucsc.edu> sirkm@ssyx.ucsc.edu (Greg Anderson) writes:
>>>TN #117 says to look at the QuickDraw variable screenbits.bounds to
>>>find the size of the screen, but on my Mac IIx, this rectangle is
>>>always (0,0,0,0) when MultiFinder is installed (color or b&w).

In article <9429@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes:
>>Uh, I really don't think so.  Check again.

In article <1102@urbana.mcd.mot.com> willcox@urbana.mcd.mot.com
(David A Willcox) writes:
>This sounds a bit like what happened when I tried to use screenBits
>from within an XCMD.  The problem, of course, was that I hadn't called
>InitGraf() (I hope that's the right name) from within my XCMD, and I
>was seeing a local copy of screenBits that had not been initialized.
>(I'm using Think C 3.0.)

When I first read this, I though, "Of course!"  But now, I'm not sure
this makes sense.  The XCMD should be called using HyperCard's A5, and
its QD globals are initialized already.  Maybe the problem is that LSC
has a bug that looks for the QD globals off A4 if you are linking a code
resource?  That wouldn't be too surprising.  But the LSC code resource
glue doesn't mess about with the caller's A5, which should remain constant
throughout.

>I tried calling InitGraf() within my XCMD, and that gave me valid
>values for screenBits, but things rapidly went to hell on return to
>HyperCard, since HyperCard's quickdraw globals didn't work any more.
>(Obvious, in hindsight.)

Sort of.  This seems to be compatible with the A4-bug hypothesis,
assuming that the code generated was using offsets from A4 and you
passed a pointer to thePort which was also A4-relative.

>Can anyone tell me, is there a better way to get at global variables
>such as screenBits from within an XCMD?

Tell me, did you try the ugly way of accessing QD globals from assembly
language, from IM I-163?  I bet it would work.
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com

"Gorbachev is returning to the heritage of the great Lenin" - Ronald Reagan