Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ucsd!swrinde!cs.utexas.edu!husc6!brauer!fry
From: fry@brauer.harvard.edu (David Fry)
Newsgroups: comp.sys.mac.programmer
Subject: Offscreen Worlds...help, please?
Message-ID: <3990@husc6.harvard.edu>
Date: 23 Aug 90 10:54:49 GMT
Sender: news@husc6.harvard.edu
Reply-To: fry@brauer.harvard.edu (David Fry)
Organization: Harvard Math Department
Lines: 105



I'm having tremendous trouble getting offscreen worlds to work in even
the least little way on my Mac IIfx (8-megs RAM, System 6.0.5, 
32bitQD 1.2 in the System Folder...makes no difference if I remove
it, all other INITs off, 8-bit graphics).  As an example, this program 
opens a small window, and draws a circle in it.  Ideally, the circle would
be drawn in an offscreen world and CopyBits-ed onto the window.
The code to do that is commented out.  However, just by including
a SetGWorld() call to my offscreen GWorld, the PaintOval call
later in the program causes the Mac to crash.  Macsbug shows
that most of my program has been converted to $FFFF's.  (Did
it try to draw the oval in code space??)

If the SetGWorld call is commented out as well, the program works.
So simply allocating and deallocating the GWorlds doesn't crash the
system.

Any ideas?  

David Fry
Harvard University
fry@math.harvard.edu

-------------------------------------------------------------

#include "color.h"
#include "colortoolbox.h"
#include "GraphDevMgr.h"

#define		NULL		0L


main()
{
	WindowPtr	theWindow;
	Rect		bounds;
	GWorldPtr	offGWorld;
	short		error;
	CGrafPtr	savePtr;
	GDHandle	saveDev;

   	InitGraf(&thePort);
    InitWindows();
    InitCursor();
    FlushEvents(everyEvent,0);

	GetGWorld(&savePtr,&saveDev);

	SetRect(&bounds,0,0,300,300);
	OffsetRect(&bounds,5,40);
		
	theWindow = NewWindow(NULL,&bounds,"\ptest of gworlds",
		TRUE,documentProc,-1L,FALSE,NULL);

	SetPort(theWindow);
	SetRect(&bounds,0,0,300,300);

	error = NewGWorld(&offGWorld,1,&bounds,NULL,NULL,0L);
	
	if ( error != noErr ) {
		DebugStr("\pAn Error!");
		SetGWorld(savePtr,saveDev);
		ExitToShell();
	}

	SetGWorld(offGWorld,NULL);	/* <---- the offender */
	
/*
	Ultimately, the circle should be drawn on the offGWorld
	and then CopyBits onto theWindow.  If I don't call
	SetGWorld directly above things are okay.  But calling
	it here, causes the PaintOval below to fail.
*/
/*
	if ( !LockPixels(offGWorld->portPixMap) ) {
		DebugStr("\p pixels purged");
		SetGWorld(savePtr,saveDev);
		ExitToShell();
	}
	
	SetRect(&bounds,0,0,300,300);	
	PaintOval(&bounds);
	UnlockPixels(offGWorld->portPixMap);
*/
		
	SetPort(theWindow);
	SetRect(&bounds,0,0,300,300);
	PaintOval(&bounds);
	
/*
	LockPixels(offGWorld->portPixMap);
	CopyBits( *(offGWorld->portPixMap), &theWindow->portBits,
		&offGWorld->portRect,&theWindow->portRect,srcCopy,NULL);
	UnlockPixels(offGWorld->portPixMap);
*/

	while ( !Button() ) {}

	DisposeGWorld(offGWorld);
	DisposeWindow(theWindow);	
	FlushEvents(everyEvent,0);
	SetGWorld(savePtr,saveDev);	

}