001// Copyright 2009, 2010, 2011 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 java.io.IOException;
018
019import org.apache.tapestry5.BindingConstants;
020import org.apache.tapestry5.Block;
021import org.apache.tapestry5.ComponentResources;
022import org.apache.tapestry5.EventConstants;
023import org.apache.tapestry5.EventContext;
024import org.apache.tapestry5.Link;
025import org.apache.tapestry5.MarkupWriter;
026import org.apache.tapestry5.TrackableComponentEventCallback;
027import org.apache.tapestry5.ajax.MultiZoneUpdate;
028import org.apache.tapestry5.annotations.Environmental;
029import org.apache.tapestry5.annotations.Events;
030import org.apache.tapestry5.annotations.Import;
031import org.apache.tapestry5.annotations.Parameter;
032import org.apache.tapestry5.annotations.SupportsInformalParameters;
033import org.apache.tapestry5.dom.Element;
034import org.apache.tapestry5.ioc.annotations.Inject;
035import org.apache.tapestry5.ioc.internal.util.InternalUtils;
036import org.apache.tapestry5.json.JSONObject;
037import org.apache.tapestry5.services.javascript.JavaScriptSupport;
038
039/**
040 * A component used to implement the <a
041 * href="http://en.wikipedia.org/wiki/Progressive_enhancement">progressive
042 * enhancement</a> web design strategy; the component renders itself with a
043 * simplified initial content (i.e., "loading
044 * ...") and an Ajax request then supplies the component's true body. This
045 * results in much faster page loads. You can
046 * even nest these!
047 * <p/>
048 * The component simply does not render its body on initial render. On the subsequent action event request, it fires a
049 * {@link org.apache.tapestry5.EventConstants#PROGRESSIVE_DISPLAY} event to inform the container about the (optional)
050 * event context. The event handler method may return a renderable object; if not then the component's body is rendered
051 * as the partial markup response.
052 * 
053 * @since 5.1.0.1
054 * @tapestrydoc
055 */
056@SupportsInformalParameters
057@Import(library = "ProgressiveDisplay.js")
058@Events(EventConstants.PROGRESSIVE_DISPLAY)
059@SuppressWarnings("all")
060public class ProgressiveDisplay
061{
062    /**
063     * The initial content to display until the real content arrives. Defaults
064     * to "Loading ..." and an Ajax activity
065     * icon.
066     */
067    @Parameter(defaultPrefix = BindingConstants.LITERAL, value = "block:defaultInitial")
068    private Block initial;
069
070    /**
071     * If provided, this is the event context, which will be provided via the
072     * {@link org.apache.tapestry5.EventConstants#PROGRESSIVE_DISPLAY event}.
073     */
074    @Parameter
075    private Object[] context;
076
077    @Inject
078    private ComponentResources resources;
079
080    @Environmental
081    private JavaScriptSupport jsSupport;
082
083    @Environmental
084    private TrackableComponentEventCallback eventCallback;
085
086    /**
087     * Name of a function on the client-side Tapestry.ElementEffect object that
088     * is invoked after the elements's body
089     * content has been updated. If not specified, then the basic "highlight"
090     * method is used, which performs a classic
091     * "yellow fade" to indicate to the user that and update has taken place.
092     */
093    @Parameter(defaultPrefix = BindingConstants.LITERAL)
094    private String update;
095
096    Block beginRender(MarkupWriter writer)
097    {
098        String clientId = jsSupport.allocateClientId(resources);
099        String elementName = resources.getElementName("div");
100
101        Element e = writer.element(elementName, "id", clientId);
102
103        resources.renderInformalParameters(writer);
104
105        e.addClassName("t-zone");
106
107        Link link = resources.createEventLink(EventConstants.ACTION, context);
108
109        JSONObject spec = new JSONObject();
110
111        if (InternalUtils.isNonBlank(update))
112            spec.put("update", update.toLowerCase());
113
114        spec.put("element", clientId);
115        spec.put("url", link.toURI());
116
117        jsSupport.addInitializerCall("progressiveDisplay", spec);
118
119        return initial;
120    }
121
122    Object onAction(EventContext context) throws IOException
123    {
124        resources.triggerContextEvent(EventConstants.PROGRESSIVE_DISPLAY, context, eventCallback);
125
126        if (eventCallback.isAborted())
127            return null;
128
129        return getBody();
130    }
131
132    boolean beforeRenderBody()
133    {
134        return false;
135    }
136
137    void afterRender(MarkupWriter writer)
138    {
139        writer.end();
140    }
141
142    /**
143     * Returns the body of the ProgressiveDisplay, which is sometimes (in the
144     * context of a {@linkplain MultiZoneUpdate multi-zone update})
145     * the content to be included.
146     * 
147     * @since 5.2.0
148     * @return body of component
149     */
150    public Block getBody()
151    {
152        return resources.getBody();
153    }
154}