gomp-20050608-branch/libjava/classpath/java/awt/GraphicsEnvironment.java

   1 /* GraphicsEnvironment.java -- information about the graphics environment
   2    Copyright (C) 2002, 2004, 2005  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 java.awt;
  40
  41 import gnu.java.awt.ClasspathToolkit;
  42 import gnu.classpath.SystemProperties;
  43 import java.awt.image.BufferedImage;
  44 import java.util.Locale;
  45
  46 /**
  47  * This descibes the collection of GraphicsDevice and Font objects available
  48  * on a given platform. The resources might be local or remote, and specify
  49  * the valid configurations for displaying graphics.
  50  *
  51  * @author Eric Blake (ebb9@email.byu.edu)
  52  * @see GraphicsDevice
  53  * @see GraphicsConfiguration
  54  * @since 1.4
  55  * @status updated to 1.4
  56  */
  57 public abstract class GraphicsEnvironment
  58 {
  59   private static GraphicsEnvironment localGraphicsEnvironment;
  60
  61   /**
  62    * The environment must be obtained from a factory or query method, hence
  63    * this constructor is protected.
  64    */
  65   protected GraphicsEnvironment()
  66   {
  67   }
  68
  69   /**
  70    * Returns the local graphics environment. If the java.awt.graphicsenv
  71    * system property is set, it instantiates the specified class,
  72    * otherwise it assume that the awt toolkit is a ClasspathToolkit
  73    * and delegates to it to create the instance.
  74    *
  75    * @return the local environment
  76    */
  77   public static GraphicsEnvironment getLocalGraphicsEnvironment()
  78   {
  79     if (localGraphicsEnvironment != null)
  80       return localGraphicsEnvironment;
  81
  82     String graphicsenv = SystemProperties.getProperty("java.awt.graphicsenv",
  83                                                       null);
  84     if (graphicsenv != null)
  85       {
  86         try
  87           {
  88             // We intentionally use the bootstrap class loader.
  89             localGraphicsEnvironment = (GraphicsEnvironment)
  90                 Class.forName(graphicsenv).newInstance();
  91             return localGraphicsEnvironment;
  92           }
  93         catch (Exception x)
  94           {
  95             throw (InternalError)
  96                 new InternalError("Unable to instantiate java.awt.graphicsenv")
  97                     .initCause(x);
  98           }
  99       }
 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