eventinfo.js

/**
 * Records information for later handling of events. This type is
 * shared, and instances of it are passed, between the eventcontract
 * and the dispatcher jsbinary. Therefore, the fields of this type are
 * referenced by string literals rather than property literals
 * throughout the code.
 *
 * 'targetElement' is the element the action occured on, 'actionElement'
 * is the element that has the jsaction handler.
 *
 * A null 'actionElement' identifies an EventInfo instance that didn't match a
 * jsaction attribute.  This allows us to execute global event handlers with the
 * appropriate event type (including a11y clicks and custom events).
 *
 * TODO(user): Using literals to access properties makes type
 * checking partially ineffective. Accessing a wrongly spelled field
 * this way doesn't create a compiler error, and passing such an
 * untyped field to a place where a type is expected doesn't create a
 * jscompiler error either. Assigning a value of the wrong type in
 * this way, however, does trigger a jscompiler error (seen when
 * assigning Event to 'target', which requires !Event).
 *
 * @typedef {{
 *   eventType: string,
 *   event: !Event,
 *   targetElement: !Element,
 *   action: string,
 *   actionElement: Element,
 *   timeStamp: number
 * }}
 */
exports.EventInfo;