On 7 Dec, 2013, at 12:46 am, Graham Cox <[email protected]> wrote:
>
>
> @synchronized( self )
> {
> CGContextDrawImage( ctx,
> tileRect, tileImage );
> }
> CGImageRelease( tileImage );
>
> free( bitsPtr );
> }];
>
> [mDrawingQueue addOperation:op];
> #else
> [self drawTile:tileRect inContext:ctx];
> #endif
>
> }
> }
> }
>
> #if DRAW_THREADED
> [mDrawingQueue waitUntilAllOperationsAreFinished];
> #endif
>
You could also, instead of synchronizing the CGContextDrawImage(), which may
make your threads wait for each other for some infinitessimal time, use
dispatch_async( dispatch_get_main_queue(), {
CGContextDrawImage( ctx, tileRect, tileImage );
CGImageRelease( tileImage );
free( bitsPtr );
}
which serializes them. And I doubt it would make a sod of difference.
For completeness, if you wanted a dispatch queue as opposed to NSOperationQueue
based approach, setting up a dispatch queue, concurrent one, and using
dispatch_apply() with iterations = tx * ty would do that, and wait for
completion, so you don't need the waitUntilAllOperationsAreFinished. But
that's just preference, I use dispatch queues when I can most of the time.
And reminded of the comment about how hard block syntax can be to remember, I
didn't make this page, I'm not a fan of the name, but it's awfully useful and I
keep it bookmarked, I tinyURLed it to avoid tripping up swear checkers,
http://tinyurl.com/m6lukyg.
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