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Tablet Events and the Responder Chain

Like any NSEvent object, tablet events are routed up the responder chain until they are handled. Responder objects in an application (that is, objects that inherit from NSResponder) can override the appropriate NSResponder methods and handle the NSEvent object that is passed to them in that method. Or they can pass the event on to the next responder in the chain. (If you don’t override one of these method, the event automatically goes to the next responder.

An application that intends to handle tablet events should override at least five NSResponder methods:

• tabletProximity: and tabletPoint:

  Implement these methods to handle native proximity and pointer tablet events.

• mouseDown:, mouseDragged:, and mouseUp:

  implement these methods to handle mouse events with a subtype of NSTabletPointEventSubtype or NSTabletProximityEventSubtype.

A recommended approach is to funnel tablet events in these methods to two common handlers, one for proximity events and the other for pointer events. If you have objects in your application that are not in the responder chain and you want these objects to know about tablet events as they arrive, you could implement your event-handler routine so that it posts a notification to all interested observers.

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