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Public API for the Apache MyFaces Trinidad project
There is a newer version: 2.2.1
/*
 * 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.
 */
package org.apache.myfaces.trinidad.component;

import java.util.Collections;
import java.util.Set;

import org.apache.myfaces.trinidad.context.RequestContext;

/**
 * ProcessingContext passed to FlattenedComponents and ComponentProcessors representing the
 * current component iteration context.
 * @see ComponentProcessor
 * @see UIXComponent#processFlattenedChildren(FacesContext, ComponentProcessor, UIComponent, Object)
 * @see UIXComponent#processFlattenedChildren(FacesContext, ComponentProcessor, Iterable, Object)
 * @see UIXComponent#processFlattenedChildren(FacesContext, ComponentProcessingContext, ComponentProcessor, UIComponent, Object)
 * @see UIXComponent#processFlattenedChildren(FacesContext, ComponentProcessingContext, ComponentProcessor, Iterable, Object)
 * @see FlattenedComponent
 */
public final class ComponentProcessingContext
{
  ComponentProcessingContext()
  {      
    _requestContext = RequestContext.getCurrentInstance();
  }

  /**
   * Hints to the the FlattenedComponents regarding what the flattened iteration is being used for,
   * The FlattenedComponent may use this information to change its flattening behavior.
   * For example, a FlattenedComponent may generate output during a PROCESS_FOR_ENCODING
   * iteration, but not during a normal iteration.
   */
  public enum ProcessingHint
  {
    /**
     * Indicates that the iteration is occurring in order to encode iterated components.  This
     * hint may only be used during the RenderResponse phase and only once per an iterated
     * component.  Due to these guarantees, the FlattenedComponent is allowed to generate
     * content during the iteration, an exception to the normal rule that iterations must
     * be idempotent in case the same component is iterated multiple times.
     */
    PROCESS_FOR_ENCODING
  }
  
  /**
   * Returns the current starting group depth of the ProcessingContext.  The starting depth is only
   * non-zero for the first rendered child inside a group or nested groups.  If two grouping
   * components, such as UIXGroup, are nested immediately inside of each other, the first processed
   * component in the second UIXGroup will see 2 for the start depth.  The second would see 0.
   * @see #getGroupDepth
   */
  public int getStartDepth()
  {
    return _startDepth;
  }
  
  /**
   * Returns the current group depth of the ProcessingContext.  The group depth is equal to the
   * nesting depth of grouping components, such as UIXGroup that the current iteratior has
   * entered.  In contrast to getStartDepth(), all siblings at a particular nesting
   * level see the same group depth.
   * @see #getStartDepth
   */
  public int getGroupDepth()
  {
    return _groupDepth;
  }

  /**
   * Returns hints that influence the behavior of the component processing
   *
   * @return a non-empty, unmodifiable collection of ProcessingHints
   */
  public Set getHints()
  {
    return _hints;
  }

  public RequestContext getRequestContext()
  {
    return _requestContext;
  }

  /**
   * Increment the grouping and startGroup states.
   * 
   * If pushGroup is called, the seubsequent code should be
   * wrapped in a try{}finally{ComponentProcessingContext.popGroup()} block to guarantee
   * that the group is popped correctly in case an exception is thrown.
   * @see #popGroup
   */
  void pushGroup()
  {
    _startDepth++;
    _groupDepth++;
  }
  
  /**
   * Decrement the grouping and startGroup states.
   * 

   * If pushGroup is called, the seubsequent code should be
   * wrapped in a try{}finally{ComponentProcessingContext.popGroup()} block to guarantee
   * that the group is popped correctly in case an exception is thrown.
   * @see #pushGroup
   */
  void popGroup()
  {
    _groupDepth--;
    
    if (_startDepth > 0)
      _startDepth--;
  }
  
  /**
   * Called by the object performing the iteration over Component instances to 
   * reset the start depth after the ChildProcessor is called on the first component at the
   * new depth.  When iterating, the iterator should place the call to resetStartDepth
   * in a finally block to guarantee that the reset happens correctly in case
   * an exception is thrown.
   */
  void resetStartDepth()
  {
    _startDepth = 0;
  }

  /**
   * Handshake from the UIXComponent
   */
  void __setIsRendering()
  {
    _hints = Collections.singleton(ProcessingHint.PROCESS_FOR_ENCODING);
  }

  private int _startDepth;
  private int _groupDepth;
  private Set _hints = Collections.emptySet();
  private RequestContext _requestContext = null;
}