[GitHub] wicket pull request #151: WICKET-6055 Made AjaxLazyLoadPanel non-blocking

[Jezza <gi...@git.apache.org>]

Github user Jezza commented on a diff in the pull request:

    https://github.com/apache/wicket/pull/151#discussion_r89122777
  
    --- Diff: wicket-extensions/src/main/java/org/apache/wicket/extensions/ajax/markup/html/AjaxLazyLoadPanel.java ---
    @@ -139,56 +182,176 @@ protected void handleCallbackScript(final IHeaderResponse response,
     	@Override
     	protected void onBeforeRender()
     	{
    -		if (state == 0)
    +		if (state == LoadingState.WAITING_FOR_LAZY_COMPONENT)
     		{
     			add(getLoadingComponent(LAZY_LOAD_COMPONENT_ID));
    -			setState((byte)1);
    +			setState(LoadingState.REPLACING_LAZY_COMPONENT);
     		}
     		super.onBeforeRender();
     	}
     
    +	@Override
    +	public void onEvent(IEvent<?> event)
    +	{
    +		super.onEvent(event);
    +
    +		if (state == LoadingState.REPLACING_LAZY_COMPONENT)
    +		{
    +			if (isReadyForReplacement())
    +			{
    +				// create the lazy load component
    +				Component component = getLazyLoadComponent(LAZY_LOAD_COMPONENT_ID);
    +
    +				// replace the spinner with the new component
    +				AjaxLazyLoadPanel.this.replace(component);
    +
    +				// mark replacement as done
    +				setState(LoadingState.REPLACEMENT_COMPLETED);
    +
    +				// remove ourselves from the timer
    +				getLazyLoadTimer().removeLazyLoadPanel(this);
    +
    +				AjaxRequestTarget target = getRequestCycle().find(AjaxRequestTarget.class);
    +
    +				// notify our subclasses of the updated component
    +				onComponentLoaded(component, target);
    +
    +				// repaint our selves if there's an AJAX request in play, otherwise let the page
    +				// redraw itself
    +				if (target != null)
    +				{
    +					target.add(AjaxLazyLoadPanel.this);
    +				}
    +			}
    +		}
    +	}
    +
    +	@Override
    +	protected void onRemove()
    +	{
    +		super.onRemove();
    +
    +		// mark replacement as done
    +		setState(LoadingState.REPLACEMENT_COMPLETED);
    +
    +		// remove ourselves from the timer
    +		AjaxLazyLoadTimer timer = getLazyLoadTimer();
    +		if (timer != null)
    +		{
    +			timer.removeLazyLoadPanel(this);
    +		}
    +	}
    +
     	/**
    +	 * Sets the new LoadingState for this panel.
     	 * 
    -	 * @param state
    +	 * @param newState
     	 */
    -	private void setState(final byte state)
    +	private void setState(final LoadingState newState)
     	{
    -		this.state = state;
    +		this.state = newState;
     		getPage().dirty();
     	}
     
     	/**
    +	 * Gets the central lazy load timer from the page if one is registered
     	 * 
    -	 * @param markupId
    -	 *            The components markupid.
    -	 * @return The component that must be lazy created. You may call setRenderBodyOnly(true) on this
    -	 *         component if you need the body only.
    +	 * @return the central lazy load timer or {@code null}
     	 */
    -	public abstract Component getLazyLoadComponent(String markupId);
    +	private AjaxLazyLoadTimer getLazyLoadTimer()
    +	{
    +		return getPage().getMetaData(AJAX_LAZY_LOAD_TIMER);
    +	}
     
     	/**
    -	 * Called when the placeholder component is replaced with the lazy loaded one.
    -	 *
    -	 * @param component
    -	 *      The lazy loaded component
    -	 * @param target
    -	 *      The Ajax request handler
    +	 * Sets the central lazy load timer on the page
    +	 * 
    +	 * @param timer
    +	 *            the timer to set
     	 */
    -	protected void onComponentLoaded(Component component, AjaxRequestTarget target)
    +	private void setLazyLoadTimer(AjaxLazyLoadTimer timer)
     	{
    +		getPage().setMetaData(AJAX_LAZY_LOAD_TIMER, timer);
     	}
     
     	/**
    -	 * @param markupId
    -	 *            The components markupid.
    -	 * @return The component to show while the real component is being created.
    +	 * @deprecated No longer called as the AjaxLazyLoadPanel uses a central AJAX timer, and it
    +	 *             doesn't make sense to modify the single timer from multiple panels
     	 */
    -	public Component getLoadingComponent(final String markupId)
    +	@SuppressWarnings("javadoc")
    +	@Deprecated
    +	protected void updateAjaxAttributes(AjaxRequestAttributes attributes)
     	{
    -		IRequestHandler handler = new ResourceReferenceRequestHandler(
    -			AbstractDefaultAjaxBehavior.INDICATOR);
    -		return new Label(markupId, "<img alt=\"Loading...\" src=\"" +
    -			RequestCycle.get().urlFor(handler) + "\"/>").setEscapeModelStrings(false);
     	}
     
    +	/**
    +	 * Allows subclasses to change the callback script if needed.
    +	 * 
    +	 * @param response
    +	 *            the current response that writes to the header
    +	 * @param callbackScript
    +	 *            the JavaScript to write in the header
    +	 * @param component
    +	 *            the component which produced the callback script
    +	 */
    +	protected void handleCallbackScript(final IHeaderResponse response,
    +		final CharSequence callbackScript, final Component component)
    +	{
    +		response.render(OnDomReadyHeaderItem.forScript(callbackScript));
    +	}
    +
    +	/**
    +	 * The AJAX timer for updating the AjaxLazyLoadPanel. Is designed to be a page-local singleton
    +	 * keeping track of multiple LazyLoadPanels using reference counting.
    +	 */
    +	private static class AjaxLazyLoadTimer extends AbstractAjaxTimerBehavior
    +	{
    +		private static final long serialVersionUID = 1L;
    +
    +		private final List<AjaxLazyLoadPanel> lazyLoadPanels = new ArrayList<>();
    +
    +		public AjaxLazyLoadTimer()
    +		{
    +			super(Duration.ONE_SECOND);
    --- End diff --
    
    Yeah, I was just about to say, why not delegate it to the page.
    That seems like a nice compromise between making sure we don't flood the server, and we can control the polling time.


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