If you want your custom view Palette to support “Size To Fit” from the Layout menu in Interface Builder add a category on your custom view in your IB Palette code that implements
Your implementation of ibSizeToFit should adjust the view’s frame to what you want it to be.
This applies to IB from 10.4 and previously.
Did you try implementing -[NSView sizeToFit]? That’s a public method that should be enough.