Examples of org.waveprotocol.wave.client.wavepanel.event.EventDispatcherPanel

org.waveprotocol.wave.client.wavepanel.event.EventDispatcherPanel

A panel that enables arbitrary event handling using a single DOM event listener.

This panel acts as a sink for all DOM events in its subtree, with a single top-level DOM event listener. Application-level event handlers register themselves with this panel against elements of a particular "kind". When a browser-event occurs, this panel traces up the DOM hierarchy from the source of the event, locating the nearest ancestor with a kind for which an event handler is registered, and dispatches the event to that handler. Dispatching continues up the DOM tree to all such element/handler pairs, until this panel's element is reached, or until a handler declares that propagation should stop. This process is analogous to the native browser mechanism of event bubbling.

This dispatch mechanism has some specific advantages and disadvantages.
Advantages:

since it uses only a single listener, with contextualization driven by data in the DOM, it is more appropriate for a page with a server-supplied rendering, since it avoids the cost of traversing the entire DOM in order to hook up individual DOM event listeners;
it reduces memory overhead; and
finally, it allows UI interaction to occur in a GWT application without using Widgets, which are relatively expensive and heavyweight.

Disadvantages:

runtime dispatch cost is slower;
mixes state and control by injecting kind values into the DOM;
event-handling setup requires global context (this object), in order to register event listeners, rather than being able to setup event-handling directly on a Widget.

   *        for the wave panel to be a root widget
   */
  public static WavePanelImpl create(
      DomAsViewProvider views, Element panelDom, LogicalPanel container) {
    Preconditions.checkArgument(panelDom != null);
    EventDispatcherPanel events =
        (container != null) ? EventDispatcherPanel.inGwtContext(panelDom, container)
            : EventDispatcherPanel.of(panelDom);
    WavePanelImpl panel = new WavePanelImpl(views, events);


    // Existing content?

   *        for the wave panel to be a root widget
   */
  public static WavePanelImpl create(
      DomAsViewProvider views, Element panelDom, LogicalPanel container) {
    Preconditions.checkArgument(panelDom != null);
    EventDispatcherPanel events =
        (container != null) ? EventDispatcherPanel.inGwtContext(panelDom, container)
            : EventDispatcherPanel.of(panelDom);
    WavePanelImpl panel = new WavePanelImpl(views, events);


    // Existing content?

Related Classes of org.waveprotocol.wave.client.wavepanel.event.EventDispatcherPanel

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