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: enter image description here

How can I achieve this?

The clip in -drawRect: affects only the view's drawing and has nothing to do with the subviews that still exist in the view's entire rectangle. The drawing isn't over the subviews, it's under them. Jason's answer is about the only way to accomplish this. Use layer-backed views. — Joshua Nozzi

Jason Harwig Jason Harwig · Accepted Answer · 2011-10-06T15:02:10

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;
}

Rounded rect on NSView that clips all containing subviews

3 Answers