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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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