001/* GraphicsEnvironment.java -- information about the graphics environment 002 Copyright (C) 2002, 2004, 2005 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 java.awt; 040 041import gnu.java.awt.ClasspathToolkit; 042import gnu.classpath.SystemProperties; 043import java.awt.image.BufferedImage; 044import java.util.Locale; 045 046/** 047 * This descibes the collection of GraphicsDevice and Font objects available 048 * on a given platform. The resources might be local or remote, and specify 049 * the valid configurations for displaying graphics. 050 * 051 * @author Eric Blake (ebb9@email.byu.edu) 052 * @see GraphicsDevice 053 * @see GraphicsConfiguration 054 * @since 1.4 055 * @status updated to 1.4 056 */ 057public abstract class GraphicsEnvironment 058{ 059 private static GraphicsEnvironment localGraphicsEnvironment; 060 061 /** 062 * The environment must be obtained from a factory or query method, hence 063 * this constructor is protected. 064 */ 065 protected GraphicsEnvironment() 066 { 067 } 068 069 /** 070 * Returns the local graphics environment. If the java.awt.graphicsenv 071 * system property is set, it instantiates the specified class, 072 * otherwise it assume that the awt toolkit is a ClasspathToolkit 073 * and delegates to it to create the instance. 074 * 075 * @return the local environment 076 */ 077 public static GraphicsEnvironment getLocalGraphicsEnvironment() 078 { 079 if (localGraphicsEnvironment != null) 080 return localGraphicsEnvironment; 081 082 String graphicsenv = SystemProperties.getProperty("java.awt.graphicsenv", 083 null); 084 if (graphicsenv != null) 085 { 086 try 087 { 088 // We intentionally use the bootstrap class loader. 089 localGraphicsEnvironment = (GraphicsEnvironment) 090 Class.forName(graphicsenv).newInstance(); 091 return localGraphicsEnvironment; 092 } 093 catch (Exception x) 094 { 095 throw (InternalError) 096 new InternalError("Unable to instantiate java.awt.graphicsenv") 097 .initCause(x); 098 } 099 } 100 else 101 { 102 ClasspathToolkit tk; 103 tk = ((ClasspathToolkit) Toolkit.getDefaultToolkit()); 104 localGraphicsEnvironment = tk.getLocalGraphicsEnvironment(); 105 return localGraphicsEnvironment; 106 } 107 } 108 109 /** 110 * Check if the local environment is headless, meaning that it does not 111 * support a display, keyboard, or mouse. Many methods in the Abstract 112 * Windows Toolkit (java.awt) throw a {@link HeadlessException} if this 113 * returns true. 114 * 115 * This method returns true if the java.awt.headless property is set 116 * to "true". 117 * 118 * @return true if the environment is headless, meaning that graphics are 119 * unsupported 120 * @since 1.4 121 */ 122 public static boolean isHeadless() 123 { 124 String headless = SystemProperties.getProperty("java.awt.headless", null); 125 return "true".equalsIgnoreCase(headless); 126 } 127 128 /** 129 * Check if the given environment is headless, meaning that it does not 130 * support a display, keyboard, or mouse. Many methods in the Abstract 131 * Windows Toolkit (java.awt) throw a {@link HeadlessException} if this 132 * returns true. This default implementation returns isHeadless(), so 133 * subclasses need only override it if they differ. 134 * 135 * @return true if the environment is headless, meaning that graphics are 136 * unsupported 137 * @since 1.4 138 */ 139 public boolean isHeadlessInstance() 140 { 141 return isHeadless(); 142 } 143 144 /** 145 * Get an array of all the GraphicsDevice objects. 146 * 147 * @return the available graphics devices, may be 0 length 148 * @throws HeadlessException if the environment is headless 149 */ 150 public abstract GraphicsDevice[] getScreenDevices(); 151 152 /** 153 * Get the default screen GraphicsDevice object. 154 * 155 * @return the default screen device 156 * @throws HeadlessException if the environment is headless 157 */ 158 public abstract GraphicsDevice getDefaultScreenDevice(); 159 160 /** 161 * Return a Graphics2D object which will render into the specified image. 162 * 163 * @param image the image to render into 164 * @return the object that renders into the image 165 */ 166 public abstract Graphics2D createGraphics(BufferedImage image); 167 168 /** 169 * Returns an array of the one-point size fonts available in this 170 * environment. From there, the user can select the font and derive the 171 * correct one of proper size and attributes, using <code>deriveFont</code>. 172 * Only one master version of each font appears in this array; if a font 173 * can be derived from another, it must be created in that way. 174 * 175 * @return the array of available fonts 176 * @see #getAvailableFontFamilyNames() 177 * @see Font#deriveFont(int, float) 178 * @since 1.2 179 */ 180 public abstract Font[] getAllFonts(); 181 182 /** 183 * Returns an array of the font family names available in this environment. 184 * This allows flexibility in choosing the style of font, while still letting 185 * the Font class decide its best match. 186 * 187 * @return the array of available font families 188 * @see #getAllFonts() 189 * @see Font#getFamily() 190 * @since 1.2 191 */ 192 public abstract String[] getAvailableFontFamilyNames(); 193 194 /** 195 * Returns an array of the font family names available in this environment, 196 * localized to the current Locale if l is non-null. This allows 197 * flexibility in choosing the style of font, while still letting the Font 198 * class decide its best match. 199 * 200 * @param l the locale to use 201 * @return the array of available font families, localized 202 * @see #getAllFonts() 203 * @see Font#getFamily() 204 * @since 1.2 205 */ 206 public abstract String[] getAvailableFontFamilyNames(Locale l); 207 208 /** 209 * Returns the point where a window should be centered. You should probably 210 * also check that the window fits within the screen bounds. The default 211 * simply returns the center of the maximum window bounds; subclasses should 212 * override this if native objects (like scrollbars) make that off-centered. 213 * 214 * @return the centering point 215 * @throws HeadlessException if the environment is headless 216 * @see #getMaximumWindowBounds() 217 * @since 1.4 218 */ 219 public Point getCenterPoint() 220 { 221 Rectangle r = getMaximumWindowBounds(); 222 return new Point(r.x + r.width / 2, r.y + r.height / 2); 223 } 224 225 /** 226 * Returns the maximum bounds for a centered window object. The default 227 * implementation simply returns the bounds of the default configuration 228 * of the default screen; subclasses should override this to if native 229 * objects (like scrollbars) reduce what is truly available. Also, 230 * subclasses should override this if the window should be centered across 231 * a multi-screen display. 232 * 233 * @return the maximum window bounds 234 * @throws HeadlessException if the environment is headless 235 * @see #getCenterPoint() 236 * @see GraphicsConfiguration#getBounds() 237 * @see Toolkit#getScreenInsets(GraphicsConfiguration) 238 * @since 1.4 239 */ 240 public Rectangle getMaximumWindowBounds() 241 { 242 return getDefaultScreenDevice().getDefaultConfiguration().getBounds(); 243 } 244} // class GraphicsEnvironment