Handle events related to mouse, keyboard, and trackpad input.
NSResponder class defines the responder chain, an ordered list of objects that respond to user events. When the user clicks the mouse button, taps on the trackpad, or presses a key, an event is generated and passed up the responder chain in search of an object that can respond to it. Any object that handles events must inherit from the
NSResponder class. The core AppKit classes,
NSView, inherit from
NSApplication object maintains a list of
NSWindow objects—one for each window belonging to the app—and each
NSWindow object maintains a hierarchy of
NSView objects. This view hierarchy is used for both drawing the user interface and for handling events.
NSWindow object handles window-level events and distributes other events to its views. An
NSWindow object also has a delegate allowing you to customize its behavior.