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From: spencer@eecs.umich.edu (Spencer W. Thomas)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Creating an offscreen pixmap
Message-ID: <SPENCER.91Mar25014604@spline.eecs.umich.edu>
Date: 25 Mar 91 06:46:04 GMT
References: <kwel1.669251989@cs7.cs.aukuni.ac.nz>
Sender: news@zip.eecs.umich.edu
Organization: University of Michigan EECS Dept
Lines: 40
In-Reply-To: kwel1@cs.aukunic.ac.nz's message of 17 Mar 91 23:19:49 GMT


Here's a hunk of Think C code that does it.  You need the 32-bit QD
header file & glue, of course (I've got that for Think C, if you've
got something else, you're on your own.)

static GWorldPtr the_world = 0L;
...
	GWorldPtr old_world;
	GDHandle old_dev;
...
		MoveTo( 20, 20 );
		DrawString( "\pPlease wait, creating bitmap..." );
	
		SetRect( &max_rect, 0, 0, 255, 127 );
		if ( NewGWorld( &the_world, 32, &max_rect, 0L, 0L, 0 )
!= noErr )
		{
			MoveTo( 20, 40 );
			DrawString( "\pNewGWorld failed, sorry.");
			return;
		}
		/* Remember the current world. */
		GetGWorld( &old_world, &old_dev );
		
		SetGWorld( the_world, 0L );
		LockPixels( the_world->portPixMap );
... draw into the pixmap ...
		UnlockPixels( the_world->portPixMap );
		SetGWorld( old_world, old_dev );
		DrawString("\p done.");

... and to copy it to the screen:
	GetPort( &curr_port );
	LockPixels( the_world->portPixMap );
	CopyBits( &the_world->portPixMap, &curr_port->portPixMap, 
				&src_rect, &max_rect, srcCopy, 0L );
	UnlockPixels( the_world->portPixMap );
--
=Spencer W. Thomas 		EECS Dept, U of Michigan, Ann Arbor, MI 48109
spencer@eecs.umich.edu		313-936-2616 (8-6 E[SD]T M-F)