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- /*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You 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.
- */
-
- /* $Id$ */
-
- package org.apache.fop.accessibility;
-
- import javax.xml.transform.Source;
- import javax.xml.transform.Templates;
- import javax.xml.transform.Transformer;
- import javax.xml.transform.TransformerConfigurationException;
- import javax.xml.transform.sax.SAXTransformerFactory;
- import javax.xml.transform.sax.TransformerHandler;
- import javax.xml.transform.stream.StreamSource;
-
- import org.xml.sax.helpers.DefaultHandler;
-
- import org.apache.fop.apps.FOPException;
- import org.apache.fop.apps.FOUserAgent;
-
- /**
- * Helper class for FOP's accessibility features.
- */
- public final class Accessibility {
-
- /** Constant string for the rendering options key to enable accessibility features. */
- public static final String ACCESSIBILITY = "accessibility";
-
- // TODO what if the default factory is not a SAXTransformerFactory?
- private static SAXTransformerFactory tfactory
- = (SAXTransformerFactory)SAXTransformerFactory.newInstance();
-
- private static Templates addPtrTemplates;
-
- private static Templates reduceFOTreeTemplates;
-
- private Accessibility() { }
-
- /**
- * Decorates the given handler so the structure tree used for accessibility
- * features can be branched off the main content stream.
- * @param handler the handler to decorate
- * @param userAgent the user agent
- * @return the decorated handler
- * @throws FOPException if an error occurs setting up the decoration
- */
- public static DefaultHandler decorateDefaultHandler(DefaultHandler handler,
- FOUserAgent userAgent) throws FOPException {
- try {
- setupTemplates();
- TransformerHandler addPtr = tfactory.newTransformerHandler(addPtrTemplates);
- Transformer reduceFOTree = reduceFOTreeTemplates.newTransformer();
- return new AccessibilityPreprocessor(addPtr, reduceFOTree, userAgent, handler);
- } catch (TransformerConfigurationException e) {
- throw new FOPException(e);
- }
- }
-
- private static synchronized void setupTemplates() throws TransformerConfigurationException {
- if (addPtrTemplates == null) {
- addPtrTemplates = loadTemplates("addPtr.xsl");
- }
- if (reduceFOTreeTemplates == null) {
- reduceFOTreeTemplates = loadTemplates("reduceFOTree.xsl");
- }
- }
-
- private static Templates loadTemplates(String source) throws TransformerConfigurationException {
- Source src = new StreamSource(Accessibility.class.getResource(source).toExternalForm());
- return tfactory.newTemplates(src);
- }
-
- }
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