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}