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