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
015package 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, Object)
025 */
026public 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
035    public String getPreloadedImageReference(String url);
036}