Seeing this as well. I'm using Swift and an NSTextView, and I'm providing autocomplete while the user types. On the call to NSTextView.complete() it will reliably show this error and, oddly, the syntax coloring I'm providing with the NSTextStorageDelegate's textContentStorage(_ textContentStorage: NSTextContentStorage, textParagraphWith range: NSRange) simultaneously stops working. Sadly neither call throws an exception so I'm unable to figure out what's actually causing the error.

Hi krzyzanowskim, Thanks for posting this. I was struggling to make the right associations between the notions of text storage vs. layout fragments, redraw notifications, etc., and also hadn't thought of using an NSRulerView for the numbers. Your approach here is much more concise and easy to implement than the one I was pursuing, and provided a lot of clarity.