libjava/classpath/javax/swing/border/AbstractBorder.java

   1 /* AbstractBorder.java --
   2    Copyright (C) 2003, 2006, Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package javax.swing.border;
  40
  41 import java.awt.Component;
  42 import java.awt.Graphics;
  43 import java.awt.Insets;
  44 import java.awt.Rectangle;
  45 import java.io.Serializable;
  46
  47
  48 /**
  49  * An invisible zero-width border, serving as a base class for
  50  * implementing more interesting borders.
  51  *
  52  * @author Sascha Brawer (brawer@dandelis.ch)
  53  * @author Ronald Veldema (rveldema@cs.vu.nl)
  54  */
  55 public abstract class AbstractBorder implements Border, Serializable
  56 {
  57   static final long serialVersionUID = -545885975315191844L;
  58
  59   /**
  60    * Constructs a new AbstractBorder.
  61    */
  62   public AbstractBorder()
  63   {
  64     // Nothing to do here.
  65   }
  66
  67   /**
  68    * Performs nothing, because the default implementation provided by
  69    * this class is an invisible, zero-width border. Subclasses will
  70    * likely want to override this method, but they are not required
  71    * to do so.
  72    *
  73    * @param c the component whose border is to be painted.
  74    * @param g the graphics for painting.
  75    * @param x the horizontal position for painting the border.
  76    * @param y the vertical position for painting the border.
  77    * @param width the width of the available area for painting the border.
  78    * @param height the height of the available area for painting the border.
  79    */
  80   public void paintBorder(Component c, Graphics g, int x, int y, int width,
  81                           int height)
  82   {
  83     // A previous version of Classpath had emitted a warning when
  84     // this method was called. The warning was removed because it is
  85     // perfectly legal for a subclass to not override the paintBorder
  86     // method. An example would be EmptyBorder.
  87   }
  88
  89   /**
  90    * Returns the insets required for drawing this border around the specified
  91    * component.
  92    *
  93    * @param c  the component that the border applies to (ignored here,
  94    *     subclasses may use it).
  95    *
  96    * @return an Insets object whose <code>left</code>, <code>right</code>,
  97    *         <code>top</code> and <code>bottom</code> fields indicate the
  98    *         width of the border at the respective edge, which is zero
  99    *         for the default implementation provided by AbstractButton.
 100    *
 101    * @see #getBorderInsets(java.awt.Component, java.awt.Insets)
 102    */
 103   public Insets getBorderInsets(Component c)
 104   {
 105     return new Insets(0, 0, 0, 0);
 106   }
 107
 108   /**
 109    * Returns the insets required for drawing this border around the specified
 110    * component.  The default implementation provided here sets the
 111    * <code>left</code>, <code>right</code>, <code>top</code> and
 112    * <code>bottom</code> fields of the passed <code>insets</code> parameter to
 113    * zero.
 114    *
 115    * @param c  the component that the border applies to (ignored here,
 116    *     subclasses may use it).
 117    * @param insets  an instance that will be overwritten and returned as the
 118    *     result (<code>null</code> not permitted).
 119    *
 120    * @return The border insets (the same object that was passed as the
 121    *     <code>insets</code> argument).
 122    *
 123    * @see #getBorderInsets(Component)
 124    *
 125    * @throws NullPointerException if <code>insets</code> is <code>null</code>.
 126    */
 127   public Insets getBorderInsets(Component c, Insets insets)
 128   {
 129     insets.left = insets.right = insets.top = insets.bottom = 0;
 130     return insets;
 131   }
 132
 133   /**
 134    * Determines whether or not this border is opaque. An opaque border
 135    * fills every pixel in its area when painting. Partially
 136    * translucent borders must return <code>false</code>, or ugly
 137    * artifacts can appear on screen. The default implementation
 138    * provided here always returns <code>false</code>.
 139    *
 140    * @return <code>false</code>.
 141    */
 142   public boolean isBorderOpaque()
 143   {
 144     return false;
 145   }
 146
 147   /**
 148    * Returns a rectangle that covers the specified area minus the insets
 149    * required to draw this border.  Components that wish to determine an area
 150    * into which they can safely draw without intersecting with a border might
 151    * want to use this helper method.
 152    *
 153    * @param c the component in the center of this border.
 154    * @param x the horizontal position of the border.
 155    * @param y the vertical position of the border.
 156    * @param width the width of the available area for the border.
 157    * @param height the height of the available area for the border.
 158    *
 159    * @return The interior rectangle.
 160    */
 161   public Rectangle getInteriorRectangle(Component c, int x, int y, int width,
 162                                         int height)
 163   {
 164     return getInteriorRectangle(c, this, x, y, width, height);
 165   }
 166
 167   /**
 168    * Returns a rectangle that covers the specified area minus the insets
 169    * required to draw the specified border (if the border is <code>null</code>,
 170    * zero insets are assumed).  Components that wish to determine an area into
 171    * which they can safely draw without intersecting with a border might want
 172    * to use this helper method.
 173    *
 174    * @param c the component in the center of this border.
 175    * @param b the border (<code>null</code> permitted).
 176    * @param x the horizontal position of the border.
 177    * @param y the vertical position of the border.
 178    * @param width the width of the available area for the border.
 179    * @param height the height of the available area for the border.
 180    *
 181    * @return The interior rectangle.
 182    */
 183   public static Rectangle getInteriorRectangle(Component c, Border b, int x,
 184                                                int y, int width, int height)
 185   {
 186     Insets borderInsets;
 187
 188     if (b != null)
 189     {
 190       borderInsets = b.getBorderInsets(c);
 191       x += borderInsets.left;
 192       y += borderInsets.top;
 193       width -= borderInsets.left + borderInsets.right;
 194       height -= borderInsets.top + borderInsets.bottom;
 195     }
 196
 197     return new Rectangle (x, y, width, height);
 198   }
 199 }