NSView add/removeSubview animated

NSView+Animations.m

@implementation NSView (Animations)

- (void)addSubview:(NSView *)aView animated:(BOOL)animated {
    [aView setAlphaValue:0.f];
    [aView setFrameOrigin:NSZeroPoint];
    
    CGFloat duration = animated ? (([[[self window] currentEvent] modifierFlags] & NSShiftKeyMask) ? 1.f : 0.25f ) : 0.f;
    [NSAnimationContext beginGrouping];
    [[NSAnimationContext currentContext] setDuration:duration];
    
    [self addSubview:aView];
    [[aView animator] setAlphaValue:1.f];
    
    [NSAnimationContext endGrouping];
}

- (void)removeFromSuperviewAnimated:(BOOL)animated {
    CGFloat duration = animated ? (([[[self window] currentEvent] modifierFlags] & NSShiftKeyMask) ? 1.f : 0.25f ) : 0.f;
    [NSAnimationContext beginGrouping];
    [[NSAnimationContext currentContext] setDuration:duration];
    
    [[self animator] setAlphaValue:0.f];
    
    [NSAnimationContext endGrouping];
    
    // if we were Lion-only, using built-in completion handler would be a better idea
    [self performSelector:@selector(removeFromSuperview)
               withObject:nil
               afterDelay:duration];
}

@end