    001// Copyright 2009-2013 The Apache Software Foundation
    002//
    003// Licensed under the Apache License, Version 2.0 (the "License");
    004// you may not use this file except in compliance with the License.
    005// You may obtain a copy of the License at
    006//
    007// http://www.apache.org/licenses/LICENSE-2.0
    008//
    009// Unless required by applicable law or agreed to in writing, software
    010// distributed under the License is distributed on an "AS IS" BASIS,
    011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012// See the License for the specific language governing permissions and
    013// limitations under the License.
    014
    015package org.apache.tapestry5.corelib.components;
    016
    017import org.apache.tapestry5.*;
    018import org.apache.tapestry5.annotations.Environmental;
    019import org.apache.tapestry5.annotations.Events;
    020import org.apache.tapestry5.annotations.Parameter;
    021import org.apache.tapestry5.annotations.SupportsInformalParameters;
    022import org.apache.tapestry5.ioc.annotations.Inject;
    023import org.apache.tapestry5.services.compatibility.DeprecationWarning;
    024import org.apache.tapestry5.services.javascript.JavaScriptSupport;
    025
    026import java.io.IOException;
    027
    028/**
    029 * A component used to implement the <a
    030 * href="http://en.wikipedia.org/wiki/Progressive_enhancement">progressive
    031 * enhancement</a> web design strategy; the component renders itself with a
    032 * simplified initial content (i.e., "loading
    033 * ...") and an Ajax request then supplies the component's true body. This
    034 * results in much faster page loads. You can
    035 * even nest these!
    036 * <p/>
    037 * The component simply does not render its body on initial render. On the subsequent action event request, it fires a
    038 * {@link org.apache.tapestry5.EventConstants#PROGRESSIVE_DISPLAY} event to inform the container about the (optional)
    039 * event context. The event handler method may return a renderable object; if not then the component's body is rendered
    040 * as the partial markup response.
    041 *
    042 * @tapestrydoc
    043 * @since 5.1.0.1
    044 */
    045@SupportsInformalParameters
    046@Events(EventConstants.PROGRESSIVE_DISPLAY)
    047@SuppressWarnings("all")
    048public class ProgressiveDisplay
    049{
    050    /**
    051     * The initial content to display until the real content arrives. Defaults
    052     * to "Loading ..." and an Ajax activity
    053     * icon.
    054     */
    055    @Parameter(defaultPrefix = BindingConstants.LITERAL, value = "block:defaultInitial")
    056    private Block initial;
    057
    058    /**
    059     * If provided, this is the event context, which will be provided via the
    060     * {@link org.apache.tapestry5.EventConstants#PROGRESSIVE_DISPLAY event}.
    061     */
    062    @Parameter
    063    private Object[] context;
    064
    065    @Inject
    066    private ComponentResources resources;
    067
    068    @Environmental
    069    private JavaScriptSupport jsSupport;
    070
    071    @Environmental
    072    private TrackableComponentEventCallback eventCallback;
    073
    074    @Inject
    075    private DeprecationWarning deprecationWarning;
    076
    077    /**
    078     * Name of a function on the client-side Tapestry.ElementEffect object that
    079     * is invoked after the elements's body
    080     * content has been updated. If not specified, then the basic "highlight"
    081     * method is used, which performs a classic
    082     * "yellow fade" to indicate to the user that and update has taken place.
    083     *
    084     * @deprecated Deprecated in 5.4 with no replacement.
    085     */
    086    @Parameter(defaultPrefix = BindingConstants.LITERAL)
    087    private String update;
    088
    089    void pageLoaded() {
    090        deprecationWarning.ignoredComponentParameters(resources, "update");
    091    }
    092
    093    Block beginRender(MarkupWriter writer)
    094    {
    095        String clientId = jsSupport.allocateClientId(resources);
    096        String elementName = resources.getElementName("div");
    097
    098        writer.element(elementName, "id", clientId, "data-container-type", "zone");
    099        resources.renderInformalParameters(writer);
    100
    101        Link link = resources.createEventLink(EventConstants.ACTION, context);
    102
    103        jsSupport.require("t5/core/zone").invoke("deferredZoneUpdate").with(clientId, link.toURI());
    104
    105        // Return the placeholder for the full content. That will render instead of the main body
    106        // of the component.
    107        return initial;
    108    }
    109
    110    Object onAction(EventContext context) throws IOException
    111    {
    112        resources.triggerContextEvent(EventConstants.PROGRESSIVE_DISPLAY, context, eventCallback);
    113
    114        if (eventCallback.isAborted())
    115            return null;
    116
    117        return getBody();
    118    }
    119
    120    boolean beforeRenderBody()
    121    {
    122        return false;
    123    }
    124
    125    void afterRender(MarkupWriter writer)
    126    {
    127        writer.end();
    128    }
    129
    130    /**
    131     * Returns the body of the ProgressiveDisplay, which is sometimes (in the
    132     * context of a
    133     * {@linkplain org.apache.tapestry5.services.ajax.AjaxResponseRenderer#addRender(org.apache.tapestry5.ClientBodyElement)} partial page render})
    134     * the content to be included.
    135     *
    136     * @return body of component
    137     * @since 5.2.0
    138     */
    139    public Block getBody()
    140    {
    141        return resources.getBody();
    142    }
    143}