001/* AbstractBorder.java -- 002 Copyright (C) 2003, 2006, 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; 044import java.awt.Rectangle; 045import java.io.Serializable; 046 047 048/** 049 * An invisible zero-width border, serving as a base class for 050 * implementing more interesting borders. 051 * 052 * @author Sascha Brawer (brawer@dandelis.ch) 053 * @author Ronald Veldema (rveldema@cs.vu.nl) 054 */ 055public abstract class AbstractBorder implements Border, Serializable 056{ 057 static final long serialVersionUID = -545885975315191844L; 058 059 /** 060 * Constructs a new AbstractBorder. 061 */ 062 public AbstractBorder() 063 { 064 // Nothing to do here. 065 } 066 067 /** 068 * Performs nothing, because the default implementation provided by 069 * this class is an invisible, zero-width border. Subclasses will 070 * likely want to override this method, but they are not required 071 * to do so. 072 * 073 * @param c the component whose border is to be painted. 074 * @param g the graphics for painting. 075 * @param x the horizontal position for painting the border. 076 * @param y the vertical position for painting the border. 077 * @param width the width of the available area for painting the border. 078 * @param height the height of the available area for painting the border. 079 */ 080 public void paintBorder(Component c, Graphics g, int x, int y, int width, 081 int height) 082 { 083 // A previous version of Classpath had emitted a warning when 084 // this method was called. The warning was removed because it is 085 // perfectly legal for a subclass to not override the paintBorder 086 // method. An example would be EmptyBorder. 087 } 088 089 /** 090 * Returns the insets required for drawing this border around the specified 091 * component. 092 * 093 * @param c the component that the border applies to (ignored here, 094 * subclasses may use it). 095 * 096 * @return an Insets object whose <code>left</code>, <code>right</code>, 097 * <code>top</code> and <code>bottom</code> fields indicate the 098 * width of the border at the respective edge, which is zero 099 * 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}