How do I receive notifications when TextKit's NSTextContainer's size changes?

Question

I need to know when TextKit's NSTextContainer's size changes, so I can update some caches in my NSLayoutManager. How can I receive notifications when size changes? Does TextKit in general (and NSTextContainer's size property specifically) support KVO? I reviewed the NSTextContainer.h header and the NSTextContainer documetation, and I can't find anything about it either way.

Answer 1

NSTextContainer is supposed to call -[NSLayoutManager textContainerChangedGeometry:] on its NSLayoutManager when its size or shape changes:

This method is invoked automatically by other components of the text system; you should rarely need to invoke it directly. Subclasses of NSTextContainer, however, must invoke this method any time their size of shape changes (a text container that dynamically adjusts its shape to wrap text around placed graphics, for example, must do so when a graphic is added, moved, or removed).

I haven't tested this to determine if it requires that heightTracksTextView or widthTracksTextView be set on the NSTextContainer; that verticallyResizable or horizontallyResizable be set on the NSLayoutManager; or that programmatically calling -[NSTextContainer setSize:] or -[NSTextContainer setSimpleRectangularTextContainer:] will automatically call -[NSLayoutManager textContainerChangedGeometry:] as advertised.