- (NSUInteger)hitTestForEvent:(NSEvent *)event inRect:(NSRect)frame ofView:(NSView *)controlView {

	NSRect checkBoxFrame = [self _checkBoxFrameForInteriorFrame:frame];

    NSPoint point = [controlView convertPoint:[event locationInWindow] fromView:nil];
    // Delegate hit testing to other cells
	if (_checkBoxCell) {
        if (NSPointInRect(point, checkBoxFrame)) {
			return NSCellHitTrackableArea;
        }
    }

    return NSCellHitNone;
}



+ (BOOL)prefersTrackingUntilMouseUp {
    // you want a single, long tracking "session" from mouse down till up
    return YES;
}

- (BOOL)startTrackingAt:(NSPoint)startPoint inView:(NSView *)controlView {

    [_checkBoxCell setHighlighted:YES];
    return YES;  // keep tracking
}

- (BOOL)continueTracking:(NSPoint)lastPoint at:(NSPoint)currentPoint inView:(NSView *)controlView {
    // if |currentPoint| is in the button, highlight it
    // otherwise, unhighlight it
    return YES;  // keep on tracking
}

- (void)stopTracking:(NSPoint)lastPoint at:(NSPoint)stopPoint inView:(NSView *)controlView mouseIsUp:(BOOL)flag {
    // if |flag| and mouse in button's rect, then
    // and, finally,
}