Rounded rect on NSView that clips all containing subviews

Question

I am creating a NSView subclass that has rounded corners. This view is meant to be a container and other subviews will be added to it. I am trying to get the rounded corners of the NSView to clip all of the subview's corners as well, but am not able to get it.

- (void)drawRect:(NSRect)dirtyRect {
    NSRect rect = [self bounds];
    NSBezierPath *path = [NSBezierPath bezierPathWithRoundedRect:rect xRadius:self.radius yRadius:self.radius];
    [path addClip];

    [[NSColor redColor] set];
    NSRectFill(dirtyRect);

    [super drawRect:dirtyRect];     
}

The red is just for example. If I add a subview to the rect, The corners are not clipped:

How can I achieve this?

Answer 1

Have you tried clipping with layers?

self.layer.cornerRadius = self.radius; self.layer.masksToBounds = YES;

---

Ah, sorry, somehow I've missed that you were talking about NSView, not UIView. It would be hard to clip NSView subviews in all cases because it seems that most of Cocoa standard views set their own clipping path. It might be easier to layout subviews with some paddings and avoid need for clipping.

Answer 2

Using Core Animation layers will clip sublayers correctly.

In your container NSView subclass:

- (id)initWithFrame:(NSRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        self.layer = _layer;   // strangely necessary
        self.wantsLayer = YES;
        self.layer.masksToBounds = YES;    
        self.layer.cornerRadius = 10.0;    
    }    
    return self;
}

Answer 3

You can do it in the interface builder without subclassing adding User Defined Runtime Attributes"