1 /*
   2  * Copyright (c) 1997, 2007, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 
  27 package javax.swing;
  28 
  29 import java.awt.*;
  30 import java.awt.event.*;
  31 import java.beans.ConstructorProperties;
  32 import java.util.Locale;
  33 import java.io.Serializable;
  34 import javax.accessibility.*;
  35 
  36 /**
  37  * A lightweight container
  38  * that uses a BoxLayout object as its layout manager.
  39  * Box provides several class methods
  40  * that are useful for containers using BoxLayout --
  41  * even non-Box containers.
  42  *
  43  * <p>
  44  * The <code>Box</code> class can create several kinds
  45  * of invisible components
  46  * that affect layout:
  47  * glue, struts, and rigid areas.
  48  * If all the components your <code>Box</code> contains
  49  * have a fixed size,
  50  * you might want to use a glue component
  51  * (returned by <code>createGlue</code>)
  52  * to control the components' positions.
  53  * If you need a fixed amount of space between two components,
  54  * try using a strut
  55  * (<code>createHorizontalStrut</code> or <code>createVerticalStrut</code>).
  56  * If you need an invisible component
  57  * that always takes up the same amount of space,
  58  * get it by invoking <code>createRigidArea</code>.
  59  * <p>
  60  * If you are implementing a <code>BoxLayout</code> you
  61  * can find further information and examples in
  62  * <a
  63  href="http://java.sun.com/docs/books/tutorial/uiswing/layout/box.html">How to Use BoxLayout</a>,
  64  * a section in <em>The Java Tutorial.</em>
  65  * <p>
  66  * <strong>Warning:</strong>
  67  * Serialized objects of this class will not be compatible with
  68  * future Swing releases. The current serialization support is
  69  * appropriate for short term storage or RMI between applications running
  70  * the same version of Swing.  As of 1.4, support for long term storage
  71  * of all JavaBeans<sup><font size="-2">TM</font></sup>
  72  * has been added to the <code>java.beans</code> package.
  73  * Please see {@link java.beans.XMLEncoder}.
  74  *
  75  * @see BoxLayout
  76  *
  77  * @author  Timothy Prinzing
  78  */
  79 @SuppressWarnings("serial")
  80 public class Box extends JComponent implements Accessible {
  81 
  82     /**
  83      * Creates a <code>Box</code> that displays its components
  84      * along the the specified axis.
  85      *
  86      * @param axis  can be {@link BoxLayout#X_AXIS},
  87      *              {@link BoxLayout#Y_AXIS},
  88      *              {@link BoxLayout#LINE_AXIS} or
  89      *              {@link BoxLayout#PAGE_AXIS}.
  90      * @throws AWTError if the <code>axis</code> is invalid
  91      * @see #createHorizontalBox
  92      * @see #createVerticalBox
  93      */
  94     public Box(int axis) {
  95         super();
  96         super.setLayout(new BoxLayout(this, axis));
  97     }
  98 
  99     /**
 100      * Creates a <code>Box</code> that displays its components
 101      * from left to right. If you want a <code>Box</code> that
 102      * respects the component orientation you should create the
 103      * <code>Box</code> using the constructor and pass in
 104      * <code>BoxLayout.LINE_AXIS</code>, eg:
 105      * <pre>
 106      *   Box lineBox = new Box(BoxLayout.LINE_AXIS);
 107      * </pre>
 108      *
 109      * @return the box
 110      */
 111     public static Box createHorizontalBox() {
 112         return new Box(BoxLayout.X_AXIS);
 113     }
 114 
 115     /**
 116      * Creates a <code>Box</code> that displays its components
 117      * from top to bottom. If you want a <code>Box</code> that
 118      * respects the component orientation you should create the
 119      * <code>Box</code> using the constructor and pass in
 120      * <code>BoxLayout.PAGE_AXIS</code>, eg:
 121      * <pre>
 122      *   Box lineBox = new Box(BoxLayout.PAGE_AXIS);
 123      * </pre>
 124      *
 125      * @return the box
 126      */
 127     public static Box createVerticalBox() {
 128         return new Box(BoxLayout.Y_AXIS);
 129     }
 130 
 131     /**
 132      * Creates an invisible component that's always the specified size.
 133      * <!-- WHEN WOULD YOU USE THIS AS OPPOSED TO A STRUT? -->
 134      *
 135      * @param d the dimensions of the invisible component
 136      * @return the component
 137      * @see #createGlue
 138      * @see #createHorizontalStrut
 139      * @see #createVerticalStrut
 140      */
 141     public static Component createRigidArea(Dimension d) {
 142         return new Filler(d, d, d);
 143     }
 144 
 145     /**
 146      * Creates an invisible, fixed-width component.
 147      * In a horizontal box,
 148      * you typically use this method
 149      * to force a certain amount of space between two components.
 150      * In a vertical box,
 151      * you might use this method
 152      * to force the box to be at least the specified width.
 153      * The invisible component has no height
 154      * unless excess space is available,
 155      * in which case it takes its share of available space,
 156      * just like any other component that has no maximum height.
 157      *
 158      * @param width the width of the invisible component, in pixels >= 0
 159      * @return the component
 160      * @see #createVerticalStrut
 161      * @see #createGlue
 162      * @see #createRigidArea
 163      */
 164     public static Component createHorizontalStrut(int width) {
 165         return new Filler(new Dimension(width,0), new Dimension(width,0),
 166                           new Dimension(width, Short.MAX_VALUE));
 167     }
 168 
 169     /**
 170      * Creates an invisible, fixed-height component.
 171      * In a vertical box,
 172      * you typically use this method
 173      * to force a certain amount of space between two components.
 174      * In a horizontal box,
 175      * you might use this method
 176      * to force the box to be at least the specified height.
 177      * The invisible component has no width
 178      * unless excess space is available,
 179      * in which case it takes its share of available space,
 180      * just like any other component that has no maximum width.
 181      *
 182      * @param height the height of the invisible component, in pixels >= 0
 183      * @return the component
 184      * @see #createHorizontalStrut
 185      * @see #createGlue
 186      * @see #createRigidArea
 187      */
 188     public static Component createVerticalStrut(int height) {
 189         return new Filler(new Dimension(0,height), new Dimension(0,height),
 190                           new Dimension(Short.MAX_VALUE, height));
 191     }
 192 
 193     /**
 194      * Creates an invisible "glue" component
 195      * that can be useful in a Box
 196      * whose visible components have a maximum width
 197      * (for a horizontal box)
 198      * or height (for a vertical box).
 199      * You can think of the glue component
 200      * as being a gooey substance
 201      * that expands as much as necessary
 202      * to fill the space between its neighboring components.
 203      *
 204      * <p>
 205      *
 206      * For example, suppose you have
 207      * a horizontal box that contains two fixed-size components.
 208      * If the box gets extra space,
 209      * the fixed-size components won't become larger,
 210     * so where does the extra space go?
 211      * Without glue,
 212      * the extra space goes to the right of the second component.
 213      * If you put glue between the fixed-size components,
 214      * then the extra space goes there.
 215      * If you put glue before the first fixed-size component,
 216      * the extra space goes there,
 217      * and the fixed-size components are shoved against the right
 218      * edge of the box.
 219      * If you put glue before the first fixed-size component
 220      * and after the second fixed-size component,
 221      * the fixed-size components are centered in the box.
 222      *
 223      * <p>
 224      *
 225      * To use glue,
 226      * call <code>Box.createGlue</code>
 227      * and add the returned component to a container.
 228      * The glue component has no minimum or preferred size,
 229      * so it takes no space unless excess space is available.
 230      * If excess space is available,
 231      * then the glue component takes its share of available
 232      * horizontal or vertical space,
 233      * just like any other component that has no maximum width or height.
 234      *
 235      * @return the component
 236      */
 237     public static Component createGlue() {
 238         return new Filler(new Dimension(0,0), new Dimension(0,0),
 239                           new Dimension(Short.MAX_VALUE, Short.MAX_VALUE));
 240     }
 241 
 242     /**
 243      * Creates a horizontal glue component.
 244      *
 245      * @return the component
 246      */
 247     public static Component createHorizontalGlue() {
 248         return new Filler(new Dimension(0,0), new Dimension(0,0),
 249                           new Dimension(Short.MAX_VALUE, 0));
 250     }
 251 
 252     /**
 253      * Creates a vertical glue component.
 254      *
 255      * @return the component
 256      */
 257     public static Component createVerticalGlue() {
 258         return new Filler(new Dimension(0,0), new Dimension(0,0),
 259                           new Dimension(0, Short.MAX_VALUE));
 260     }
 261 
 262     /**
 263      * Throws an AWTError, since a Box can use only a BoxLayout.
 264      *
 265      * @param l the layout manager to use
 266      */
 267     public void setLayout(LayoutManager l) {
 268         throw new AWTError("Illegal request");
 269     }
 270 
 271     /**
 272      * Paints this <code>Box</code>.  If this <code>Box</code> has a UI this
 273      * method invokes super's implementation, otherwise if this
 274      * <code>Box</code> is opaque the <code>Graphics</code> is filled
 275      * using the background.
 276      *
 277      * @param g the <code>Graphics</code> to paint to
 278      * @throws NullPointerException if <code>g</code> is null
 279      * @since 1.6
 280      */
 281     protected void paintComponent(Graphics g) {
 282         if (ui != null) {
 283             // On the off chance some one created a UI, honor it
 284             super.paintComponent(g);
 285         } else if (isOpaque()) {
 286             g.setColor(getBackground());
 287             g.fillRect(0, 0, getWidth(), getHeight());
 288         }
 289     }
 290 
 291 
 292     /**
 293      * An implementation of a lightweight component that participates in
 294      * layout but has no view.
 295      * <p>
 296      * <strong>Warning:</strong>
 297      * Serialized objects of this class will not be compatible with
 298      * future Swing releases. The current serialization support is
 299      * appropriate for short term storage or RMI between applications running
 300      * the same version of Swing.  As of 1.4, support for long term storage
 301      * of all JavaBeans<sup><font size="-2">TM</font></sup>
 302      * has been added to the <code>java.beans</code> package.
 303      * Please see {@link java.beans.XMLEncoder}.
 304      */
 305     @SuppressWarnings("serial")
 306     public static class Filler extends JComponent implements Accessible {
 307 
 308         /**
 309          * Constructor to create shape with the given size ranges.
 310          *
 311          * @param min   Minimum size
 312          * @param pref  Preferred size
 313          * @param max   Maximum size
 314          */
 315         @ConstructorProperties({"minimumSize", "preferredSize", "maximumSize"})
 316         public Filler(Dimension min, Dimension pref, Dimension max) {
 317             setMinimumSize(min);
 318             setPreferredSize(pref);
 319             setMaximumSize(max);
 320         }
 321 
 322         /**
 323          * Change the size requests for this shape.  An invalidate() is
 324          * propagated upward as a result so that layout will eventually
 325          * happen with using the new sizes.
 326          *
 327          * @param min   Value to return for getMinimumSize
 328          * @param pref  Value to return for getPreferredSize
 329          * @param max   Value to return for getMaximumSize
 330          */
 331         public void changeShape(Dimension min, Dimension pref, Dimension max) {
 332             setMinimumSize(min);
 333             setPreferredSize(pref);
 334             setMaximumSize(max);
 335             revalidate();
 336         }
 337 
 338         // ---- Component methods ------------------------------------------
 339 
 340         /**
 341          * Paints this <code>Filler</code>.  If this
 342          * <code>Filler</code> has a UI this method invokes super's
 343          * implementation, otherwise if this <code>Filler</code> is
 344          * opaque the <code>Graphics</code> is filled using the
 345          * background.
 346          *
 347          * @param g the <code>Graphics</code> to paint to
 348          * @throws NullPointerException if <code>g</code> is null
 349          * @since 1.6
 350          */
 351         protected void paintComponent(Graphics g) {
 352             if (ui != null) {
 353                 // On the off chance some one created a UI, honor it
 354                 super.paintComponent(g);
 355             } else if (isOpaque()) {
 356                 g.setColor(getBackground());
 357                 g.fillRect(0, 0, getWidth(), getHeight());
 358             }
 359         }
 360 
 361 /////////////////
 362 // Accessibility support for Box$Filler
 363 ////////////////
 364 
 365         /**
 366          * Gets the AccessibleContext associated with this Box.Filler.
 367          * For box fillers, the AccessibleContext takes the form of an
 368          * AccessibleBoxFiller.
 369          * A new AccessibleAWTBoxFiller instance is created if necessary.
 370          *
 371          * @return an AccessibleBoxFiller that serves as the
 372          *         AccessibleContext of this Box.Filler.
 373          */
 374         public AccessibleContext getAccessibleContext() {
 375             if (accessibleContext == null) {
 376                 accessibleContext = new AccessibleBoxFiller();
 377             }
 378             return accessibleContext;
 379         }
 380 
 381         /**
 382          * This class implements accessibility support for the
 383          * <code>Box.Filler</code> class.
 384          */
 385         @SuppressWarnings("serial")
 386         protected class AccessibleBoxFiller extends AccessibleAWTComponent {
 387             // AccessibleContext methods
 388             //
 389             /**
 390              * Gets the role of this object.
 391              *
 392              * @return an instance of AccessibleRole describing the role of
 393              *   the object (AccessibleRole.FILLER)
 394              * @see AccessibleRole
 395              */
 396             public AccessibleRole getAccessibleRole() {
 397                 return AccessibleRole.FILLER;
 398             }
 399         }
 400     }
 401 
 402 /////////////////
 403 // Accessibility support for Box
 404 ////////////////
 405 
 406     /**
 407      * Gets the AccessibleContext associated with this Box.
 408      * For boxes, the AccessibleContext takes the form of an
 409      * AccessibleBox.
 410      * A new AccessibleAWTBox instance is created if necessary.
 411      *
 412      * @return an AccessibleBox that serves as the
 413      *         AccessibleContext of this Box
 414      */
 415     public AccessibleContext getAccessibleContext() {
 416         if (accessibleContext == null) {
 417             accessibleContext = new AccessibleBox();
 418         }
 419         return accessibleContext;
 420     }
 421 
 422     /**
 423      * This class implements accessibility support for the
 424      * <code>Box</code> class.
 425      */
 426     @SuppressWarnings("serial")
 427     protected class AccessibleBox extends AccessibleAWTContainer {
 428         // AccessibleContext methods
 429         //
 430         /**
 431          * Gets the role of this object.
 432          *
 433          * @return an instance of AccessibleRole describing the role of the
 434          *   object (AccessibleRole.FILLER)
 435          * @see AccessibleRole
 436          */
 437         public AccessibleRole getAccessibleRole() {
 438             return AccessibleRole.FILLER;
 439         }
 440     } // inner class AccessibleBox
 441 }