closure example

foo.m

- (void)check:(NSEvent *)event onCard:(void (^)(SMCardID, CGPoint))cardHandler onPile:(void (^)(SMPile, CGPoint))pileHandler
{
    CGPoint where = [event locationInWindow];

    [[self openGLContext] makeCurrentContext];
    glBindBuffer(GL_PIXEL_PACK_BUFFER, _pbo);
    uint32_t const *pickData = glMapBuffer(GL_PIXEL_PACK_BUFFER, GL_READ_ONLY);
    uint32_t pixel = pickData[(size_t)where.x + 1024 * (size_t)where.y];
    glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
    glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
    
    uint32_t r = (pixel >> 16) & 0xff;
    CGPoint st = CGPointMake(
        ((pixel >> 8) & 0xff) / 255.0,
        1.0 - ((pixel >> 0) & 0xff) / 255.0);
    if (r != 0)
    {
        SMCardID cardID = (r / 2) - 1;
        if (cardID < 104)
        {
            cardHandler(cardID, st);
        }
        else
        {
            assert(cardID < 104 + SMPileCount);
            pileHandler(cardID - 104, st);
        }
    }
}


- (void)mouseDown:(NSEvent *)event
{
    [self check:event
        onCard:^(SMCardID cardID, CGPoint st)
        {
            // NSLog(@"%C%@", SMSuitToChar([_game suitOfFaceUpCard:cardID]), SMRankToString([_game rankOfFaceUpCard:cardID]));
            _floating = cardID;
            _floatingOffset = st;
            [self setFloatingPos:event];
            [self setNeedsDisplay:YES];
        }
        onPile:^(SMPile pile, CGPoint st)
        {
            // nothing
        }];
}

otherwise.m

- (void)check:(NSEvent *)event wasCard:(BOOL*)wasCard outCardID:(SMCardID*)outCardID outPile:(SMPile*)outPile outPoint:(CGPoint*)outPoint
{
    CGPoint where = [event locationInWindow];

    [[self openGLContext] makeCurrentContext];
    glBindBuffer(GL_PIXEL_PACK_BUFFER, _pbo);
    uint32_t const *pickData = glMapBuffer(GL_PIXEL_PACK_BUFFER, GL_READ_ONLY);
    uint32_t pixel = pickData[(size_t)where.x + 1024 * (size_t)where.y];
    glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
    glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);
    
    uint32_t r = (pixel >> 16) & 0xff;
    CGPoint st = CGPointMake(
        ((pixel >> 8) & 0xff) / 255.0,
        1.0 - ((pixel >> 0) & 0xff) / 255.0);
    if (r != 0)
    {
        *outPoint = st;
        SMCardID cardID = (r / 2) - 1;
        if (cardID < 104)
        {
            *wasCard = YES;
            *outCardID = cardID;
        }
        else
        {
            assert(cardID < 104 + SMPileCount);
            *wasCard = NO;
            *outPileID = cardID - 104;
        }
    }
}


- (void)mouseDown:(NSEvent *)event
{
    BOOL wasCard;
    SMCardID cardID;
    SMPile pile;
    CGPoint st;
    [self check:event wasCard:&wasCard outCardID:&cardID outPile:&pile outPoint:&st];
    if (wasCard)
    {
        // NSLog(@"%C%@", SMSuitToChar([_game suitOfFaceUpCard:cardID]), SMRankToString([_game rankOfFaceUpCard:cardID]));
        _floating = cardID;
        _floatingOffset = st;
        [self setFloatingPos:event];
        [self setNeedsDisplay:YES];
    }
    else
    {
        // nothing
    }
}