001    // Copyright 2005 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    
015    package org.apache.tapestry;
016    
017    /**
018     * Extends {@link org.apache.tapestry.IScriptProcessor} with a handful of additional methods
019     * needed when rendering a page response.
020     * 
021     * @author Howard M. Lewis Ship
022     * @since 4.0
023     * @see org.apache.tapestry.html.Body
024     * @see org.apache.tapestry.TapestryUtils#getPageRenderSupport(IRequestCycle, IComponent)
025     */
026    public interface PageRenderSupport extends IScriptProcessor
027    {
028        /**
029         * Sets up the given URL to preload, and returns a reference to the loaded image, in the form of
030         * a snippet of JavaScript expression that can be inserted into some larger block of JavaScript
031         * as a function parameter, or as a property assignment. A typical return value might be
032         * <code>tapestry_preload[7].src</code>.
033         *
034         * @param url
035         *          The url to the resource to be preloaded.
036         * @return Reference to preload image url.
037         * @deprecated To be removed in 4.2, use {@link #getPreloadedImageReference(IComponent, String)} 
038         *              or {@link #getPreloadedImageReference(IComponent, IAsset)} instead.
039         */
040    
041        String getPreloadedImageReference(String url);
042        
043        /**
044         * Operates in the same way that {@link #getPreloadedImageReference(IComponent, String)} does, except 
045         * the source is the actual {@link IAsset} of an image to preload. 
046         * 
047         * @param target
048         *          The component the asset is being loaded for.
049         * @param source
050         *          The asset image to preload.
051         * @return The url representing the image that can be safely retrieved by the browser to see it.
052         */
053        String getPreloadedImageReference(IComponent target, IAsset source);
054        
055        /**
056         * Sets up the given URL to preload, and returns a reference to the loaded image, in the form of
057         * a snippet of JavaScript expression that can be inserted into some larger block of JavaScript
058         * as a function parameter, or as a property assignment. A typical return value might be
059         * <code>tapestry_preload[7].src</code>.
060         * 
061         * @param target
062         *          The component url being loaded for.
063         * @param url
064         *          The asset URL to preload.
065         * @return Reference to preload image url.
066         */
067        
068        String getPreloadedImageReference(IComponent target, String url);
069    }