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From: David A Lyons <dlyons@apple.com>
Subject: Re: how to get info from Window Record?
Sender: news@gallant.apple.com
Message-ID: <1994Jan28.233506.15925@gallant.apple.com>
X-Useragent: Version 1.1.3
Date: Fri, 28 Jan 1994 23:35:06 GMT
X-Xxdate: Fri, 28 Jan 94 22:22:15 GMT
References: <2iakd0$btp@TAMUTS.TAMU.EDU>
Organization: Apple Computer, Inc.
Lines: 65

In article <2iakd0$btp@TAMUTS.TAMU.EDU> Jason Perez,
j0p7771@TAMUTS.TAMU.EDU writes:
> [...]
>     CtlRecHndl frameControl,tmp;
>     unsigned long *ctlPtr;
> 	GrafPortPtr bWinPtr;
> 
>     frameControl = (CtlRecHndl)
NewHandle(sizeof(CtlRec),bannerID,0xC010,NULL);
>     tmp = (CtlRecHndl) NewHandle(sizeof(CtlRec),bannerID,0xC010,NULL);
>     bWinPtr = NewWindow(&bWin);
>     ctlPtr = (unsigned long *) (bWinPtr + 0x00CAL); /*offset to Handle

	/

>     frameControl = (CtlRecHndl) (*ctlPtr); /*get Handle */
> /*now go through all controls */
>     for (tmp = frameControl;tmp != 0L; tmp = (*tmp)->ctlNext) {
>             if ((long) ((*tmp)->ctlProc) == scrollProc) {
>                     fprintf(fout,"found a scrollbar:
%#x\n",(*tmp)->ctlFlag);
>             }
>     }
> 
>   this code just doesn't seem to work.  sometimes it will not find the
> end of the list, other times it will find only one control with a
> ctlProc value of $05000000 (what's this?).  any help much appreciated.

Aha!  It took me *three* tries to come up with the right answer on this
one.  First, I was going to tell you to use GetWControls (but that's for
content controls, and there is no corresponding call for the frame
control list).  Second, I was going to tell you that you had to subtract
4 from the offsets on page 52-15 into the window record, because the
window pointer points to the window's grafport at offset 4 (but you
already have the right offset for wFrameCtls).

So!  The magic phrase is (bWinPtr + 0x00CAL), which is an example of C
pointer arithmetic.  If bWinPtr was a pointer to a one-byte value (char

	), then your code would work.  But bWinPtr is a GrafPort *, so it points

to objects that are 170 bytes in size.

So the compiler correctly tries to be helpful, and it computes a value
that points $CA grafports higher in memory ($CA * 170 = 34340 bytes),
which is not exactly what you wanted.

You can instead do: 

     ctlPtr = (unsigned long *) (((char *) bWinPtr) + 0xCA);

Or, better yet, skip a couple steps and go straight from the window
pointer to the frame control handle (and wind up with legible code):

     frameControl = ((WindRecPtr) bWinPtr)->wFrameCtrls;

By the way, your frameControl=NewHandle and tmp=NewHandle statements
serve no purpose (except to allocate memory that you will never use). 
Those lines can simply go away.

By the other way, $05000000 is not a valid ctlProc; it's just garbage you
stumbled across by traversing random memory as if it were a linked list
of control records (you probably saw other values too, but this one
looked close to what you were searching for).

Dave Lyons, dlyons@apple.com
Mr Tangent

My opinions are my own, not Apple's.