001/* EmptyBorder.java -- 
002   Copyright (C) 2003 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package javax.swing.border;
040
041import java.awt.Component;
042import java.awt.Graphics;
043import java.awt.Insets;
044
045
046/**
047 * A border for leaving a specifiable number of pixels empty around
048 * the enclosed component.  An EmptyBorder requires some space on each
049 * edge, but does not perform any drawing.
050 *
051 * <p><img src="EmptyBorder-1.png" width="290" height="200"
052 * alt="[An illustration of EmptyBorder]" />
053 *
054 * @author Sascha Brawer (brawer@dandelis.ch)
055 */
056public class EmptyBorder extends AbstractBorder
057{
058  /**
059   * Determined using the <code>serialver</code> tool
060   * of Apple/Sun JDK 1.3.1 on MacOS X 10.1.5.
061   */
062  static final long serialVersionUID = -8116076291731988694L;
063
064
065  /**
066   * The number of pixels required at the left edge.
067   */
068  protected int left;
069
070
071  /**
072   * The number of pixels required at the right edge.
073   */
074  protected int right;
075
076
077  /**
078   * The number of pixels required at the top edge.
079   */
080  protected int top;
081
082
083  /**
084   * The number of pixels required at the bottom edge.
085   */
086  protected int bottom;
087
088
089  /**
090   * Constructs an empty border given the number of pixels required
091   * on each side.
092   *
093   * @param top the number of pixels that the border will need
094   *        for its top edge.
095   *
096   * @param left the number of pixels that the border will need
097   *        for its left edge.
098   *
099   * @param bottom the number of pixels that the border will need
100   *        for its bottom edge.
101   *
102   * @param right the number of pixels that the border will need
103   *        for its right edge.
104   */
105  public EmptyBorder(int top, int left, int bottom, int right)
106  {
107    this.top = top;
108    this.left = left;
109    this.bottom = bottom;
110    this.right = right;
111  }
112
113
114  /**
115   * Constructs an empty border given the number of pixels required
116   * on each side, passed in an Insets object.
117   *
118   * @param borderInsets the Insets for the new border.
119   */
120  public EmptyBorder(Insets borderInsets)
121  {
122    this(borderInsets.top, borderInsets.left,
123         borderInsets.bottom, borderInsets.right);
124  }
125
126
127  /**
128   * Performs nothing because an EmptyBorder does not paint any
129   * pixels. While the inherited implementation provided by
130   * {@link AbstractBorder#paintBorder} is a no-op as well,
131   * it is overwritten in order to match the API of the Sun
132   * reference implementation.
133   *
134   * @param c the component whose border is to be painted.
135   * @param g the graphics for painting.
136   * @param x the horizontal position for painting the border.
137   * @param y the vertical position for painting the border.
138   * @param width the width of the available area for painting the border.
139   * @param height the height of the available area for painting the border.
140   */
141  public void paintBorder(Component c, Graphics g,
142                          int x, int y, int width, int height)
143  {
144    // Nothing to do here.
145  }
146
147
148  /**
149   * Measures the width of this border.
150   *
151   * @param c the component whose border is to be measured.
152   *
153   * @return an Insets object whose <code>left</code>, <code>right</code>,
154   *         <code>top</code> and <code>bottom</code> fields indicate the
155   *         width of the border at the respective edge.
156   *
157   * @see #getBorderInsets(java.awt.Component, java.awt.Insets)
158   */
159  public Insets getBorderInsets(Component c)
160  {
161    return getBorderInsets(c, null);
162  }
163
164
165  /**
166   * Measures the width of this border, storing the results into a
167   * pre-existing Insets object.
168   *
169   * @param insets an Insets object for holding the result values.
170   *        After invoking this method, the <code>left</code>,
171   *        <code>right</code>, <code>top</code> and
172   *        <code>bottom</code> fields indicate the width of the
173   *        border at the respective edge.
174   *
175   * @return the same object that was passed for <code>insets</code>.
176   *
177   * @see #getBorderInsets()
178   */
179  public Insets getBorderInsets(Component c, Insets insets)
180  {
181    if (insets == null)
182      insets = new Insets(0, 0, 0, 0);
183
184    insets.left = left;
185    insets.right = right;
186    insets.top = top;
187    insets.bottom = bottom;
188    return insets;
189  }
190
191
192  /**
193   * Measures the width of this border.
194   *
195   * @return an Insets object whose <code>left</code>, <code>right</code>,
196   *         <code>top</code> and <code>bottom</code> fields indicate the
197   *         width of the border at the respective edge.
198   *
199   * @see #getBorderInsets(java.awt.Component, java.awt.Insets)
200   */
201  public Insets getBorderInsets()
202  {
203    return getBorderInsets(null, null);
204  }
205  
206  
207  /**
208   * Determines whether this border fills every pixel in its area
209   * when painting. Since an empty border does not paint any pixels
210   * whatsoever, the result is <code>false</code>.
211   *
212   * @return <code>false</code>.
213   */
214  public boolean isBorderOpaque()
215  {
216    /* The inherited implementation of AbstractBorder.isBorderOpaque()
217     * would also return false. It is not clear why this is overriden
218     * in the Sun implementation, at least not from just reading the
219     * JavaDoc.
220     */
221    return false;
222  }
223}