code: /*
   * 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.xalan.trace;
  
  
  /**
   * Interface the XSL processor calls when it matches a source node, selects a set of source nodes,
   * or generates a result node.
   * If you want an object instance to be called when a trace event occurs, use the TransformerImpl setTraceListener method.
   * @see org.apache.xalan.trace.TracerEvent
   * @see org.apache.xalan.trace.TraceManager#addTraceListener
   * @xsl.usage advanced
   */
  public interface TraceListener extends java.util.EventListener
  {
  
    /**
     * Method that is called when a trace event occurs.
     * The method is blocking.  It must return before processing continues.
     *
     * @param ev the trace event.
     */
    public void trace(TracerEvent ev);
  
    /**
     * Method that is called just after the formatter listener is called.
     *
     * @param ev the generate event.
     *
     * @throws javax.xml.transform.TransformerException
     */
    public void selected(SelectionEvent ev) throws javax.xml.transform.TransformerException;
  
    /**
     * Method that is called just after the formatter listener is called.
     *
     * @param ev the generate event.
     */
    public void generated(GenerateEvent ev);
  }
  