In a Cocoa app, I'm trying to get notified when the user clicks outside of
the current responder view.
The purpose is to check the validity of input before performing the click.
For example, a NSTextField is the current responder. If the user clicks on a
NSButton, since the NSButton can't become responder, the NSTextField is not
notified. I'm looking for a generic way to tell the NSTextField to check
itself, and maybe filter the click.
I was expecting textShouldEndEditing to be called, but it appears that it's
called only when another responder is about to become the current ...