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}