gcc/libjava/javax/swing/border/EmptyBorder.java

/* EmptyBorder.java -- 
   Copyright (C) 2003 Free Software Foundation, Inc.

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
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General Public License for more details.

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02111-1307 USA.

Linking this library statically or dynamically with other modules is
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permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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package javax.swing.border;

import java.awt.Component;
import java.awt.Graphics;
import java.awt.Insets;


/**
 * A border for leaving a specifiable number of pixels empty around
 * the enclosed component.  An EmptyBorder requires some space on each
 * edge, but does not perform any drawing.
 *
 * <p><img src="EmptyBorder-1.png" width="290" height="200"
 * alt="[An illustration of EmptyBorder]" />
 *
 * @author Sascha Brawer (brawer@dandelis.ch)
 */
public class EmptyBorder
  extends AbstractBorder
{
  /**
   * Determined using the <code>serialver</code> tool
   * of Apple/Sun JDK 1.3.1 on MacOS X 10.1.5.
   */
  static final long serialVersionUID = -8116076291731988694L;


  /**
   * The number of pixels required at the left edge.
   */
  protected int left;


  /**
   * The number of pixels required at the right edge.
   */
  protected int right;


  /**
   * The number of pixels required at the top edge.
   */
  protected int top;


  /**
   * The number of pixels required at the bottom edge.
   */
  protected int bottom;


  /**
   * Constructs an empty border given the number of pixels required
   * on each side.
   *
   * @param top the number of pixels that the border will need
   *        for its top edge.
   *
   * @param left the number of pixels that the border will need
   *        for its left edge.
   *
   * @param bottom the number of pixels that the border will need
   *        for its bottom edge.
   *
   * @param right the number of pixels that the border will need
   *        for its right edge.
   */
  public EmptyBorder(int top, int left, int bottom, int right)
  {
    this.top = top;
    this.left = left;
    this.bottom = bottom;
    this.right = right;
  }


  /**
   * Constructs an empty border given the number of pixels required
   * on each side, passed in an Insets object.
   *
   * @param borderInsets the Insets for the new border.
   */
  public EmptyBorder(Insets borderInsets)
  {
    this(borderInsets.top, borderInsets.left,
         borderInsets.bottom, borderInsets.right);
  }


  /**
   * Performs nothing because an EmptyBorder does not paint any
   * pixels. While the inherited implementation provided by
   * {@link AbstractBorder#paintBorder} is a no-op as well,
   * it is overwritten in order to match the API of the Sun
   * reference implementation.
   *
   * @param c the component whose border is to be painted.
   * @param g the graphics for painting.
   * @param x the horizontal position for painting the border.
   * @param y the vertical position for painting the border.
   * @param width the width of the available area for painting the border.
   * @param height the height of the available area for painting the border.
   */
  public void paintBorder(Component c, Graphics g,
                          int x, int y, int width, int height)
  {
  }


  /**
   * Measures the width of this border.
   *
   * @param c the component whose border is to be measured.
   *
   * @return an Insets object whose <code>left</code>, <code>right</code>,
   *         <code>top</code> and <code>bottom</code> fields indicate the
   *         width of the border at the respective edge.
   *
   * @see #getBorderInsets(java.awt.Component, java.awt.Insets)
   */
  public Insets getBorderInsets(Component c)
  {
    return getBorderInsets(c, null);
  }


  /**
   * Measures the width of this border, storing the results into a
   * pre-existing Insets object.
   *
   * @param insets an Insets object for holding the result values.
   *        After invoking this method, the <code>left</code>,
   *        <code>right</code>, <code>top</code> and
   *        <code>bottom</code> fields indicate the width of the
   *        border at the respective edge.
   *
   * @return the same object that was passed for <code>insets</code>.
   *
   * @see #getBorderInsets()
   */
  public Insets getBorderInsets(Component c, Insets insets)
  {
    if (insets == null)
      insets = new Insets(0, 0, 0, 0);

    insets.left = left;
    insets.right = right;
    insets.top = top;
    insets.bottom = bottom;
    return insets;
  }


  /**
   * Measures the width of this border.
   *
   * @return an Insets object whose <code>left</code>, <code>right</code>,
   *         <code>top</code> and <code>bottom</code> fields indicate the
   *         width of the border at the respective edge.
   *
   * @see #getBorderInsets(java.awt.Component, java.awt.Insets)
   */
  public Insets getBorderInsets()
  {
    return getBorderInsets(null, null);
  }
  
  
  /**
   * Determines whether this border fills every pixel in its area
   * when painting. Since an empty border does not paint any pixels
   * whatsoever, the result is <code>false</code>.
   *
   * @return <code>false</code>.
   */
  public boolean isBorderOpaque()
  {
    /* The inherited implementation of AbstractBorder.isBorderOpaque()
     * would also return false. It is not clear why this is overriden
     * in the Sun implementation, at least not from just reading the
     * JavaDoc.
     */
    return false;
  }
}