This section extends the topic of event processing started in Chapter 2 with a look at the processing of gadget-related events. The events gadgets can respond to are specified by keywords assigned to the first-level subscript descended from their EVENT attribute nodes. Once event processing has been activated, events may occur for a gadget as the result of user interaction with them, or the execution of an ETRIGGER that references one of their EVENT attribute nodes. Focus must be directed to an active gadget (the value of ^$DI($PD,"FOCUS") contains the gadget's name) before a user can trigger an event for it. An event triggered by an ETRIGGER command can occur for any gadget regardless of focus, and the value of ^$DI($PD,"FOCUS") will remain unchanged.

The developer can define the events a gadget can receive callback processing for by assigning matching-event-type keywords as subscripts to its EVENT attribute node. An application can trigger a particular event through the execution of an ETRIGGER command with the desired EVENT attribute node specified in its argument. Example 5.7 shows an EVENT attribute node.

^$W(<span class="emphasis"><iwindow name</i></span> "G" <span class="emphasis"><igadget name,</i></span> "EVENT" <span class="emphasis"><ievent type<span class="emphasis"><i)</i></span>=</i></span>value