/**
 * Copyright 2010 Google Inc.
 *
 * Licensed 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.waveprotocol.wave.client.paging;

/**
 * A unit of paging.  A block's state is potentially dynamic; its
 * {@link #getStart() start} and {@link #getEnd() end} may change over time.
 *
 */
public interface Block extends Region, TreeNode {

  /**
   * Pages this block in.  Does not page in any child blocks.
   */
  void pageIn();

  /**
   * Pages this block out. Does not page out child blocks. This method is only
   * to be called if all child blocks are paged out. Block implementations may
   * choose to throw an exception if any child blocks are still paged in.
   */
  void pageOut();

  /**
   * @return the origin, relative to which the positions of this block's
   *         children are expressed.
   */
  double getChildrenOrigin();

  //
  // Covariant overrides.
  //

  @Override
  Block getFirstChild();

  @Override
  Block getLastChild();

  @Override
  Block getNextSibling();

  @Override
  Block getPreviousSibling();

  @Override
  Block getParent();

}