Why The Bits

gistfile1.txt

typedef enum {
    BKSlideDirectionRight = 1 << 0,
    BKSlideDirectionLeft  = 1 << 1,
    BKSlideDirectionUp    = 1 << 2,
    BKSlideDirectionDown  = 1 << 3,
    
    BKSlideDirectionVertical = BKSlideDirectionUp | BKSlideDirectionDown,
    BKSlideDirectionHorizontal = BKSlideDirectionLeft | BKSlideDirectionRight
} BKSlideDirection;

BK_EXTERN BKSlideDirection BKSlideOrientation(BKSlideDirection direction);
BK_EXTERN BKSlideDirection BKSlideOtherDirection(BKSlideDirection direction);
BK_EXTERN BOOL BKSlideIsDirection(BKSlideDirection check, BKSlideDirection direction);
BK_EXTERN CGPoint BKSlideOffscreenCenterPoint(CGRect enclosingFrame, CGRect frame, BKSlideDirection direction);
BK_EXTERN CGPoint CGPointCenterOfRect(CGRect frame);



.m file


BK_EXTERN BOOL BKSlideIsDirection(BKSlideDirection check, BKSlideDirection direction) {
    BOOL value = (check | direction) == check;
    return value;
}

BK_EXTERN BKSlideDirection BKSlideOrientation(BKSlideDirection direction) {
    if ((direction | BKSlideDirectionHorizontal) == BKSlideDirectionHorizontal) {
        return BKSlideDirectionHorizontal;
    } else {
        return BKSlideDirectionVertical;
    }
}

BK_EXTERN BKSlideDirection BKSlideOtherDirection(BKSlideDirection direction) {
    BKSlideDirection orientation = BKSlideOrientation(direction);
    return (direction ^ orientation);
}

BK_EXTERN CGPoint CGPointCenterOfRect(CGRect frame) {
    return CGPointMake(frame.origin.x + (frame.size.width / 2), 
                       frame.origin.y + (frame.size.height / 2));
}

BK_EXTERN CGPoint BKSlideOffscreenCenterPoint(CGRect enclosingFrame, CGRect frame, BKSlideDirection direction) {

    // In theory this might handle diagonals too, but the mask would need to be altered.
    CGPoint offscreenCenter = CGPointCenterOfRect(frame);
    if (BKSlideIsDirection(BKSlideDirectionVertical, direction)) {
        CGFloat shift = frame.size.height / 2;
        
        if (BKSlideIsDirection(BKSlideDirectionUp, direction)) {
            offscreenCenter.y = enclosingFrame.origin.y - shift;
        } else if (BKSlideIsDirection(BKSlideDirectionDown, direction)) {
            offscreenCenter.y = enclosingFrame.size.height + shift;
        }
    }
    if (BKSlideIsDirection(BKSlideDirectionHorizontal, direction)) {
        CGFloat shift = frame.size.width / 2;
        
        if (BKSlideIsDirection(BKSlideDirectionRight, direction)) {
            offscreenCenter.x = enclosingFrame.size.width + shift;
        } else if (BKSlideIsDirection(BKSlideDirectionLeft, direction)) {
            offscreenCenter.y = enclosingFrame.origin.x - shift;
        }
    }
    return offscreenCenter;
}