gcc/libjava/java/awt/ComponentOrientation.java

/* ComponentOrientation.java -- describes a component's orientation
   Copyright (C) 2000, 2001, 2002 Free Software Foundation

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.awt;

import java.io.Serializable;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.ResourceBundle;

/**
 * This class is used to differentiate different orientations for text layout.
 * It controls whether text flows left-to-right or right-to-left, and whether
 * lines are horizontal or vertical, as in this table:<br>
 * <pre>
 * LT      RT      TL      TR
 * A B C   C B A   A D G   G D A
 * D E F   F E D   B E H   H E B
 * G H I   I H G   C F I   I F C
 * </pre>
 * <b>LT</b> languages are most common (left-to-right lines, top-to-bottom).
 * This includes Western European languages, and optionally includes Japanese,
 * Chinese, and Korean. <b>RT</b> languages (right-to-left lines,
 * top-to-bottom) are mainly middle eastern, such as Hebrew and Arabic.
 * <b>TR</b> languages flow top-to-bottom in a line, right-to-left, and are
 * the basis of Japanese, Chinese, and Korean. Finally, <b>TL</b> languages
 * flow top-to-bottom in a line, left-to-right, as in Mongolian.
 *
 * <p>This is a pretty poor excuse for a type-safe enum, since it is not
 * guaranteed that orientation objects are unique (thanks to serialization),
 * yet there is no equals() method. You would be wise to compare the output
 * of isHorizontal() and isLeftToRight() rather than comparing objects with
 * ==, especially since more constants may be added in the future.
 *
 * @author Bryce McKinlay <bryce@albatross.co.nz>
 * @since 1.0
 * @status updated to 1.4
 */
public final class ComponentOrientation implements Serializable
{
  /**
   * Compatible with JDK 1.0+.
   */
  private static final long serialVersionUID = -4113291392143563828L;

  /** Constant for unknown orientation. */
  private static final int UNKNOWN_ID = 1;

  /** Constant for horizontal line orientation. */
  private static final int HORIZONTAL_ID = 2;

  /** Constant for left-to-right orientation. */
  private static final int LEFT_TO_RIGHT_ID = 4;

  /**
   * Items run left to right, and lines flow top to bottom. Examples: English,
   * French.
   */
  public static final ComponentOrientation LEFT_TO_RIGHT
    = new ComponentOrientation(HORIZONTAL_ID | LEFT_TO_RIGHT_ID);

  /**
   * Items run right to left, and lines flow top to bottom. Examples: Arabic,
   * Hebrew.
   */
  public static final ComponentOrientation RIGHT_TO_LEFT
    = new ComponentOrientation(HORIZONTAL_ID);

  /**
   * The orientation is unknown for the locale. For backwards compatibility,
   * this behaves like LEFT_TO_RIGHT in the instance methods.
   */
  public static final ComponentOrientation UNKNOWN
    = new ComponentOrientation(UNKNOWN_ID | HORIZONTAL_ID | LEFT_TO_RIGHT_ID);

  /**
   * The orientation of this object; bitwise-or of unknown (1), horizontal (2),
   * and left-to-right (4).
   *
   * @serial the orientation
   */
  private final int orientation;

  /**
   * Construct a given orientation.
   *
   * @param orientation the orientation
   */
  private ComponentOrientation(int orientation)
  {
    this.orientation = orientation;
  }

  /**
   * Returns true if the lines are horizontal, in which case lines flow
   * top-to-bottom. For example, English, Hebrew. Counterexamples: Japanese,
   * Chinese, Korean, Mongolian.
   *
   * @return true if this orientation has horizontal lines
   */
  public boolean isHorizontal()
  {
    return (orientation & HORIZONTAL_ID) != 0;
  }

  /**
   * If isHorizontal() returns true, then this determines whether items in
   * the line flow left-to-right. If isHorizontal() returns false, items in
   * a line flow top-to-bottom, and this determines if lines flow
   * left-to-right.
   *
   * @return true if this orientation flows left-to-right
   */
  public boolean isLeftToRight()
  {
    return (orientation & LEFT_TO_RIGHT_ID) != 0;
  }

  /**
   * Gets an orientation appropriate for the locale.
   *
   * @param locale the locale
   * @return the orientation for that locale
   * @throws NullPointerException if locale is null
   */
  public static ComponentOrientation getOrientation(Locale locale)
  {
    // Based on iterating over all languages defined in JDK 1.4, this behavior
    // matches Sun's. However, it makes me wonder if any non-horizontal
    // orientations even exist, as it sure contradicts their documentation.
    String language = locale.getLanguage();
    if ("ar".equals(language) || "fa".equals(language) || "iw".equals(language)
        || "ur".equals(language))
      return RIGHT_TO_LEFT;
    return LEFT_TO_RIGHT;
  }

  /**
   * Gets an orientation from a resource bundle. This tries the following:<ol>
   * <li>Use the key "Orientation" to find an instance of ComponentOrientation
   * in the bundle.</li>
   * <li>Get the locale of the resource bundle, and get the orientation of
   * that locale.</li>
   * <li>Give up and get the orientation of the default locale.<li>
   * <ol>
   *
   * @param bdl the bundle to use
   * @return the orientation
   * @throws NullPointerException if bdl is null
   * @deprecated use {@link #getOrientation(Locale)} instead
   */
  public static ComponentOrientation getOrientation(ResourceBundle bdl)
  {
    ComponentOrientation r;
    try
      {
        r = (ComponentOrientation) bdl.getObject("Orientation");
        if (r != null)
          return r;
      }
    catch (MissingResourceException ignored)
      {
      }
    catch (ClassCastException ignored)
      {
      }
    try
      {
        r = getOrientation(bdl.getLocale());
        if (r != null)
          return r;
      }
    catch (Exception ignored)
      {
      }
    return getOrientation(Locale.getDefault());
  }
} // class ComponentOrientation