Postponed Rendering

gistfile1.m

- (void)display
{
	dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, NULL);
	dispatch_async(queue, ^{
		size_t contextWidth = [self boundsWidth];
		size_t contextHeight = [self boundsHeight];
		CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
		CGContextRef context = CGBitmapContextCreate(NULL, contextWidth, contextHeight, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);
		CGColorSpaceRelease(colorSpace);
		
		[self drawInContext:context];
		CGImageRef image = CGBitmapContextCreateImage(context);
		CGContextRelease(context);
		
		dispatch_async(dispatch_get_main_queue(), ^{
			[self setContents:(id)image];
			CGImageRelease(image);
		});
	});
}