Tells the delegate that the Save panel is about to expand or collapse because the user clicked the disclosure triangle that displays or hides the file browser.
For NSOpenPanel delegates, asks the delegate whether the specified URL should be enabled in the panel. This method is not called for NSSavePanel delegates; all URLs are always disabled.
For NSSavePanel delegates, asks the delegate for file URL validation when the user chooses the Save button. For NSOpenPanel delegates, asks the delegate for file URL validation once for each selected filename (or directory) when the user chooses the Open button.
Informs the delegate that the user changed the selected directory to the directory located at the specified URL. The URL may be nil if the current URL can’t be represented by an NSURL object.