tapestry/tapestry-framework/src/java/org/apache/tapestry/html/Rollover.java

// Copyright 2004, 2005 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package org.apache.tapestry.html;

import org.apache.hivemind.ApplicationRuntimeException;
import org.apache.tapestry.*;
import org.apache.tapestry.components.ILinkComponent;
import org.apache.tapestry.form.IFormComponent;
import org.apache.tapestry.form.LinkSubmit;

import java.util.HashMap;
import java.util.Map;

/**
 * Combines a link component (such as
 * {@link org.apache.tapestry.link.DirectLink}) with an <img> and
 * JavaScript code to create a rollover effect that works with both Netscape
 * Navigator and Internet Explorer. [ <a
 * href="../../../../../ComponentReference/Rollover.html">Component Reference
 * </a>]
 *
 * @author Howard Lewis Ship
 */

public abstract class Rollover extends AbstractComponent
{

    /**
     * Converts an {@link IAsset}binding into a usable URL. Returns null if the
     * binding does not exist or the binding's value is null.
     *
     * @param asset
     *          The asset to generate a url for.
     * @return The url to the asset resource, or null if it couldn't be generated.
     */

    protected String getAssetURL(IAsset asset)
    {
        if (asset == null)
            return null;

        return asset.buildURL();
    }

    protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
    {
        // No body, so we skip it all if not rewinding
        // (assumes no side effects on accessors).

        if (cycle.isRewinding())
            return;

        String imageURL = null;
        String mouseOverURL = null;
        String mouseOutURL = null;
        boolean dynamic = false;
        String imageId;
        boolean linkDisabled = false;

        PageRenderSupport pageRenderSupport = TapestryUtils.getPageRenderSupport(cycle, this);

        Object serviceLink = cycle.getAttribute(Tapestry.LINK_COMPONENT_ATTRIBUTE_NAME);
        if (serviceLink == null)
        {
            serviceLink = cycle.getAttribute(LinkSubmit.ATTRIBUTE_NAME);

            if (serviceLink != null)
                linkDisabled = ((IFormComponent) serviceLink).isDisabled();
        } else
        {
            linkDisabled = ((ILinkComponent) serviceLink).isDisabled();
        }

        if (serviceLink == null)
            throw new ApplicationRuntimeException(Tapestry.getMessage("Rollover.must-be-contained-by-link"), this, null, null);

        if (linkDisabled)
        {
            imageURL = getAssetURL(getDisabled());

            if (imageURL == null)
                imageURL = getAssetURL(getImage());
        }
        else
        {
            imageURL = getAssetURL(getImage());
            mouseOverURL = getAssetURL(getMouseOver());
            mouseOutURL = getAssetURL(getMouseOut());

            dynamic = (mouseOverURL != null) || (mouseOutURL != null);
        }

        if (imageURL == null)
            throw Tapestry.createRequiredParameterException(this, "image");

        writer.beginEmpty("img");

        writer.attribute("src", imageURL);

        if (dynamic)
        {
            if (mouseOverURL == null)
                mouseOverURL = imageURL;

            if (mouseOutURL == null)
                mouseOutURL = imageURL;

            imageId = writeScript(cycle, pageRenderSupport, serviceLink, mouseOverURL, mouseOutURL);

            writer.attribute("id", imageId);
        }

        renderInformalParameters(writer, cycle);

        writer.closeTag();

    }

    // Injected

    public abstract IScript getScript();

    private String writeScript(IRequestCycle cycle, PageRenderSupport pageRenderSupport,
                               Object link, String mouseOverImageURL, String mouseOutImageURL)
    {
        String imageId = pageRenderSupport.getUniqueString(getId());

        String preloadedMouseOverImageURL = pageRenderSupport.getPreloadedImageReference(this, mouseOverImageURL);
        String preloadedMouseOutImageURL = pageRenderSupport.getPreloadedImageReference(this, mouseOutImageURL);

        Map symbols = new HashMap();

        symbols.put("link", link);
        symbols.put("imageId", imageId);
        symbols.put("mouseOverImageURL", preloadedMouseOverImageURL);
        symbols.put("mouseOutImageURL", preloadedMouseOutImageURL);

        getScript().execute(this, cycle, pageRenderSupport, symbols);

        return imageId;
    }

    public abstract IAsset getMouseOut();

    public abstract IAsset getDisabled();

    public abstract IAsset getMouseOver();

    public abstract IAsset getImage();
}