    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.http.Link;
    021import org.apache.tapestry5.ioc.annotations.Inject;
    022import org.apache.tapestry5.services.compatibility.DeprecationWarning;
    023import org.apache.tapestry5.services.javascript.JavaScriptSupport;
    024
    025import java.io.IOException;
    026
    027/**
    028 * A component used to implement the <a
    029 * href="http://en.wikipedia.org/wiki/Progressive_enhancement">progressive
    030 * enhancement</a> web design strategy; the component renders itself with a
    031 * simplified initial content (i.e., "loading
    032 * ...") and an Ajax request then supplies the component's true body. This
    033 * results in much faster page loads. You can
    034 * even nest these!
    035 *
    036 * The component simply does not render its body on initial render. On the subsequent action event request, it fires a
    037 * {@link org.apache.tapestry5.EventConstants#PROGRESSIVE_DISPLAY} event to inform the container about the (optional)
    038 * event context. The event handler method may return a renderable object; if not then the component's body is rendered
    039 * as the partial markup response.
    040 *
    041 * @tapestrydoc
    042 * @since 5.1.0.1
    043 */
    044@SupportsInformalParameters
    045@Events(EventConstants.PROGRESSIVE_DISPLAY)
    046@SuppressWarnings("all")
    047public class ProgressiveDisplay
    048{
    049    /**
    050     * The initial content to display until the real content arrives. Defaults
    051     * to "Loading ..." and an Ajax activity
    052     * icon.
    053     */
    054    @Parameter(defaultPrefix = BindingConstants.LITERAL, value = "block:defaultInitial")
    055    private Block initial;
    056
    057    /**
    058     * If provided, this is the event context, which will be provided via the
    059     * {@link org.apache.tapestry5.EventConstants#PROGRESSIVE_DISPLAY event}.
    060     */
    061    @Parameter
    062    private Object[] context;
    063
    064    @Inject
    065    private ComponentResources resources;
    066
    067    @Environmental
    068    private JavaScriptSupport jsSupport;
    069
    070    @Environmental
    071    private TrackableComponentEventCallback eventCallback;
    072
    073    @Inject
    074    private DeprecationWarning deprecationWarning;
    075
    076    /**
    077     * Name of a function on the client-side Tapestry.ElementEffect object that
    078     * is invoked after the elements's body
    079     * content has been updated. If not specified, then the basic "highlight"
    080     * method is used, which performs a classic
    081     * "yellow fade" to indicate to the user that and update has taken place.
    082     *
    083     * @deprecated Deprecated in 5.4 with no replacement.
    084     */
    085    @Parameter(defaultPrefix = BindingConstants.LITERAL)
    086    private String update;
    087
    088    void pageLoaded() {
    089        deprecationWarning.ignoredComponentParameters(resources, "update");
    090    }
    091
    092    Block beginRender(MarkupWriter writer)
    093    {
    094        String clientId = jsSupport.allocateClientId(resources);
    095        String elementName = resources.getElementName("div");
    096
    097        writer.element(elementName, "id", clientId, "data-container-type", "zone");
    098        resources.renderInformalParameters(writer);
    099
    100        Link link = resources.createEventLink(EventConstants.ACTION, context);
    101
    102        jsSupport.require("t5/core/zone").invoke("deferredZoneUpdate").with(clientId, link.toURI());
    103
    104        // Return the placeholder for the full content. That will render instead of the main body
    105        // of the component.
    106        return initial;
    107    }
    108
    109    Object onAction(EventContext context) throws IOException
    110    {
    111        resources.triggerContextEvent(EventConstants.PROGRESSIVE_DISPLAY, context, eventCallback);
    112
    113        if (eventCallback.isAborted())
    114            return null;
    115
    116        return getBody();
    117    }
    118
    119    boolean beforeRenderBody()
    120    {
    121        return false;
    122    }
    123
    124    void afterRender(MarkupWriter writer)
    125    {
    126        writer.end();
    127    }
    128
    129    /**
    130     * Returns the body of the ProgressiveDisplay, which is sometimes (in the
    131     * context of a
    132     * {@linkplain org.apache.tapestry5.services.ajax.AjaxResponseRenderer#addRender(org.apache.tapestry5.ClientBodyElement)} partial page render})
    133     * the content to be included.
    134     *
    135     * @return body of component
    136     * @since 5.2.0
    137     */
    138    public Block getBody()
    139    {
    140        return resources.getBody();
    141    }
    142}