Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!udel!rochester!rit!cci632!ph
From: ph@cci632.UUCP (Pete Hoch)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Offscreen Worlds...help, please?
Summary: Only set gWorld to offscreen when drawing to offscreen.
Message-ID: <39461@cci632.UUCP>
Date: 23 Aug 90 21:15:33 GMT
References: <3990@husc6.harvard.edu>
Organization: Computer Consoles Inc. an STC Company, Rochester, NY
Lines: 58

In article <3990@husc6.harvard.edu>, fry@brauer.harvard.edu (David Fry) writes:

David is having trouble with offscreen gWorlds and keeping the right
graphics device active.  I hacked up his code below.

> Any ideas?  

> David Fry
> Harvard University
> fry@math.harvard.edu



> main()
> {

  [ variable definitions and basic initilization. ]

> 	GetGWorld(&savePtr,&saveDev);

  [ call to NewWindow and NewGWorld. ]


> 	SetGWorld(offGWorld,NULL);	/* <---- the offender */
	                                      No it isn't

> 	if ( !LockPixels(offGWorld->portPixMap) ) {
> 		SetGWorld(savePtr,saveDev);
> 		ExitToShell();
> 	}

> 	SetRect(&bounds,0,0,300,300);	
> 	PaintOval(&bounds);
> 	UnlockPixels(offGWorld->portPixMap);


> 	SetPort(theWindow);
        ^^^^^^^  Here is the problem.  SetPort is not enough.  You must
   first use SetGworld so that the graphics device is set back to a screen
   device and not an offscreen device as it is now.

  try this instead.
       SetGWorld( theWindow, saveDev);

> 	LockPixels(offGWorld->portPixMap);
> 	CopyBits( *(offGWorld->portPixMap), &theWindow->portBits,
> 		&offGWorld->portRect,&theWindow->portRect,srcCopy,NULL);

  Without setting the device to the screen the copybits call will fail.

> 	UnlockPixels(offGWorld->portPixMap);

 [ remainder of program unimportant. ]




Pete Hoch