Extent.java

/**
 * 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.waveprotocol.wave.client.scroll;

/**
 * An immutable, one-dimensional region.
 *
 * @author hearnden@google.com (David Hearnden)
 */
public final class Extent {
  private final double start;
  private final double end;

  private Extent(double start, double end) {
    this.start = start;
    this.end = end;
  }

  public static Extent of(double start, double end) {
    return new Extent(start, end);
  }

  public double getStart() {
    return start;
  }

  public double getEnd() {
    return end;
  }

  public double getSize() {
    return end - start;
  }

  public Extent scale(double s) {
    double mid = (end + start) / 2;
    double half = s * (end - start) / 2;
    return Extent.of(mid -half, mid + half);
  }

  @Override
  public String toString() {
    return "[" + start + ", " + end + "]";
  }
}