How do you change the state of the window close button in Cocoa?
cocoa, objective-c
Solution
To set it programmatically, you can use the `-setDocumentEdited:` method of NSWindow. If you are writing a Document-based app, NSDocumentManager should automatically detect when there are unsaved changes to the NSUndoManager associated with the current NSDocument.
Problem
In Cocoa Applications, you often see a little red dot in the window's close button when you have unsaved data; TextEdit is a good example of this. I've pored through the Cocoa documentation but I can't find a way to programmatically set this state. I'm sure there's some really easy way to do it, but obviously I'm missing something.