tapestry/tapestry-framework/src/java/org/apache/tapestry/PageRenderSupport.java

// Copyright 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;

/**
 * Extends {@link org.apache.tapestry.IScriptProcessor} with a handful of additional methods
 * needed when rendering a page response.
 * 
 * @author Howard M. Lewis Ship
 * @since 4.0
 * @see org.apache.tapestry.html.Body
 * @see org.apache.tapestry.TapestryUtils#getPageRenderSupport(IRequestCycle, IComponent)
 */
public interface PageRenderSupport extends IScriptProcessor
{
    /**
     * Sets up the given URL to preload, and returns a reference to the loaded image, in the form of
     * a snippet of JavaScript expression that can be inserted into some larger block of JavaScript
     * as a function parameter, or as a property assignment. A typical return value might be
     * <code>tapestry_preload[7].src</code>.
     *
     * @param url
     *          The url to the resource to be preloaded.
     * @return Reference to preload image url.
     * @deprecated To be removed in 4.2, use {@link #getPreloadedImageReference(IComponent, String)} 
     *              or {@link #getPreloadedImageReference(IComponent, IAsset)} instead.
     */

    String getPreloadedImageReference(String url);
    
    /**
     * Operates in the same way that {@link #getPreloadedImageReference(IComponent, String)} does, except 
     * the source is the actual {@link IAsset} of an image to preload. 
     * 
     * @param target
     *          The component the asset is being loaded for.
     * @param source
     *          The asset image to preload.
     * @return The url representing the image that can be safely retrieved by the browser to see it.
     */
    String getPreloadedImageReference(IComponent target, IAsset source);
    
    /**
     * Sets up the given URL to preload, and returns a reference to the loaded image, in the form of
     * a snippet of JavaScript expression that can be inserted into some larger block of JavaScript
     * as a function parameter, or as a property assignment. A typical return value might be
     * <code>tapestry_preload[7].src</code>.
     * 
     * @param target
     *          The component url being loaded for.
     * @param url
     *          The asset URL to preload.
     * @return Reference to preload image url.
     */
    
    String getPreloadedImageReference(IComponent target, String url);
}