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.
The panel asking whether the URL should be enabled.
url
The URL to be checked.
Return Value
YES to allow the URL to be enabled in the panel; otherwise, NO.
Discussion
Implementations of this method should be fast to avoid stalling the user interface. Use panel:validateURL:error: instead if processing will take a long time.
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.
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.