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1: /* ComponentUI.java -- 2: Copyright (C) 2002, 2003, 2004 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 javax.swing.plaf; 40: 41: import java.awt.Color; 42: import java.awt.Dimension; 43: import java.awt.Graphics; 44: import java.awt.Rectangle; 45: 46: import javax.accessibility.Accessible; 47: import javax.swing.JComponent; 48: 49: /** 50: * The abstract base class for all delegates that provide the 51: * pluggable look and feel for Swing components. User applications 52: * should not need to access this class; it is internal to Swing 53: * and the look-and-feel implementations. 54: * 55: * <p><img src="doc-files/ComponentUI-1.png" width="700" height="550" 56: * alt="[UML diagram illustrating the architecture for pluggable 57: * look and feels]" /></p> 58: * 59: * <p>Components such as {@link javax.swing.JSlider} do not directly 60: * implement operations related to the look and feel of the user 61: * interface, such as painting or layout. Instead, they use a delegate 62: * object for all such tasks. In the case of <code>JSlider</code>, the 63: * user interface would be provided by some concrete subclass of 64: * {@link javax.swing.plaf.SliderUI}. 65: * 66: * <p>Soon after its creation, a <code>ComponentUI</code> will be sent 67: * an {@link #installUI} message. The <code>ComponentUI</code> will 68: * react by setting properties such as the border or the background 69: * color of the <code>JComponent</code> for which it provides its 70: * services. Soon before the end of its lifecycle, the 71: * <code>ComponentUI</code> will receive an {@link #uninstallUI} 72: * message, at which time the <code>ComponentUI</code> is expected to 73: * undo any changes.</p> 74: * 75: * <p>Note that the <code>ui</code> of a <code>JComponent</code> 76: * changes whenever the user switches between look and feels. For 77: * example, the <code>ui</code> property of a <code>JSlider</code> 78: * could change from an instance of <code>MetalSliderUI</code> to an 79: * instance of <code>FooSliderUI</code>. This switch can happen at any 80: * time, but it will always be performed from inside the Swing thread.</p> 81: * 82: * @author Sascha Brawer (brawer@dandelis.ch) 83: */ 84: public abstract class ComponentUI 85: { 86: /** 87: * Constructs a new UI delegate. 88: */ 89: public ComponentUI() 90: { 91: // Nothing to do here. 92: } 93: 94: 95: /** 96: * Sets up the specified component so it conforms the the design 97: * guidelines of the implemented look and feel. When the look and 98: * feel changes, a <code>ComponentUI</code> delegate is created. 99: * The delegate object then receives an <code>installUI</code> 100: * message. 101: * 102: * <p>This method should perform the following tasks:</p> 103: * 104: * <ul> 105: * <li>Set visual properties such as borders, fonts, colors, or 106: * icons. However, no change should be performed for those 107: * properties whose values have been directly set by the client 108: * application. To allow the distinction, LookAndFeels are expected 109: * to use values that implement the {@link UIResource} marker 110: * interface, such as {@link BorderUIResource} or {@link 111: * ColorUIResource}.</li> 112: * <li>If necessary, install a {@link java.awt.LayoutManager}.</li> 113: * <li>Embed custom sub-components. For instance, the UI delegate 114: * for a {@link javax.swing.JSplitPane} might install a special 115: * component for the divider.</li> 116: * <li>Register event listeners.</li> 117: * <li>Set up properties related to keyborad navigation, such as 118: * mnemonics or focus traversal policies.</li> 119: * </ul> 120: * 121: * @param c the component for which this delegate will provide 122: * services. 123: * 124: * @see #uninstallUI 125: * @see javax.swing.JComponent#setUI 126: * @see javax.swing.JComponent#updateUI 127: */ 128: public void installUI(JComponent c) 129: { 130: // The default implementation does not change any properties. 131: } 132: 133: 134: /** 135: * Puts the specified component into the state it had before 136: * {@link #installUI} was called. 137: * 138: * @param c the component for which this delegate has provided 139: * services. 140: * 141: * @see #installUI 142: * @see javax.swing.JComponent#setUI 143: * @see javax.swing.JComponent#updateUI 144: */ 145: public void uninstallUI(JComponent c) 146: { 147: // The default implementation does not change any properties. 148: } 149: 150: 151: /** 152: * Paints the component according to the design guidelines 153: * of the look and feel. Most subclasses will want to override 154: * this method. 155: * 156: * @param g the graphics for painting. 157: * 158: * @param c the component for which this delegate performs 159: * services. 160: */ 161: public void paint(Graphics g, JComponent c) 162: { 163: // Nothing is done here. This method is meant to be overridden by 164: // subclasses. 165: } 166: 167: 168: /** 169: * Fills the specified component with its background color 170: * (unless the <code>opaque</code> property is <code>false</code>) 171: * before calling {@link #paint}. 172: * 173: * <p>It is unlikely that a subclass needs to override this method. 174: * The actual rendering should be performed by the {@link #paint} 175: * method. 176: * 177: * @param g the graphics for painting. 178: * 179: * @param c the component for which this delegate performs 180: * services. 181: * 182: * @see #paint 183: * @see javax.swing.JComponent#paintComponent 184: */ 185: public void update(Graphics g, JComponent c) 186: { 187: if (c.isOpaque()) 188: { 189: Color oldColor = g.getColor(); 190: g.setColor(c.getBackground()); 191: g.fillRect(0, 0, c.getWidth(), c.getHeight()); 192: g.setColor(oldColor); 193: } 194: paint(g, c); 195: } 196: 197: /** 198: * Determines the preferred size of a component. The default 199: * implementation returns <code>null</code>, which means that 200: * <code>c</code>’s layout manager should be asked to 201: * calculate the preferred size. 202: * 203: * @param c the component for which this delegate performs services. 204: * 205: * @return the preferred size, or <code>null</code> to indicate that 206: * <code>c</code>’s layout manager should be asked 207: * for the preferred size. 208: */ 209: public Dimension getPreferredSize(JComponent c) 210: { 211: return null; 212: } 213: 214: 215: /** 216: * Determines the minimum size of a component. The default 217: * implementation calls {@link #getPreferredSize}, but subclasses 218: * might want to override this. 219: * 220: * @param c the component for which this delegate performs services. 221: * 222: * @return the minimum size, or <code>null</code> to indicate that 223: * <code>c</code>’s layout manager should be asked 224: * to calculate the minimum size. 225: */ 226: public Dimension getMinimumSize(JComponent c) 227: { 228: return getPreferredSize(c); 229: } 230: 231: 232: /** 233: * Determines the maximum size of a component. The default 234: * implementation calls {@link #getPreferredSize}, but subclasses 235: * might want to override this. 236: * 237: * @param c the component for which this delegate performs services. 238: * 239: * @return the maximum size, or <code>null</code> to indicate that 240: * <code>c</code>’s layout manager should be asked 241: * to calculate the maximum size. 242: */ 243: public Dimension getMaximumSize(JComponent c) 244: { 245: return getPreferredSize(c); 246: } 247: 248: 249: /** 250: * Determines whether a click into the component at a specified 251: * location is considered as having hit the component. The default 252: * implementation checks whether the point falls into the 253: * component’s bounding rectangle. Some subclasses might want 254: * to override this, for example in the case of a rounded button. 255: * 256: * @param c the component for which this delegate performs services. 257: * 258: * @param x the x coordinate of the point, relative to the local 259: * coordinate system of the component. Zero would be be 260: * component’s left edge, irrespective of the location 261: * inside its parent. 262: * 263: * @param y the y coordinate of the point, relative to the local 264: * coordinate system of the component. Zero would be be 265: * component’s top edge, irrespective of the location 266: * inside its parent. 267: */ 268: public boolean contains(JComponent c, int x, int y) 269: { 270: /* JComponent.contains calls the ui delegate for hit 271: * testing. Therefore, endless mutual recursion would result if we 272: * called c.contains(x, y) here. 273: * 274: * The previous Classpath implementation called the deprecated 275: * method java.awt.Component.inside. In the Sun implementation, it 276: * can be observed that inside, other than contains, does not call 277: * the ui delegate. But that inside() behaves different to 278: * contains() clearly is in violation of the method contract, and 279: * it is not something that a good implementation should rely upon 280: * -- even if Classpath ends up being forced to replicate this 281: * apparent bug of the Sun implementation. 282: */ 283: return (x >= 0) && (x < c.getWidth()) 284: && (y >= 0) && (y < c.getHeight()); 285: } 286: 287: 288: /** 289: * Creates a delegate object for the specified component. Users 290: * should use the <code>createUI</code> method of a suitable 291: * subclass. The implementation of <code>ComponentUI</code> 292: * always throws an error. 293: * 294: * @param c the component for which a UI delegate is requested. 295: */ 296: public static ComponentUI createUI(JComponent c) 297: { 298: throw new Error( 299: "javax.swing.plaf.ComponentUI does not implement createUI; call " 300: + "createUI on a subclass."); 301: } 302: 303: 304: /** 305: * Counts the number of accessible children in the component. The 306: * default implementation delegates the inquiry to the {@link 307: * javax.accessibility.AccessibleContext} of <code>c</code>. 308: * 309: * @param c the component whose accessible children 310: * are to be counted. 311: */ 312: public int getAccessibleChildrenCount(JComponent c) 313: { 314: return c.getAccessibleContext().getAccessibleChildrenCount(); 315: } 316: 317: 318: /** 319: * Returns the specified accessible child of the component. The 320: * default implementation delegates the inquiry to the {@link 321: * javax.accessibility.AccessibleContext} of <code>c</code>. 322: * 323: * @param i the index of the accessible child, starting at zero. 324: * 325: * @param c the component whose <code>i</code>-th accessible child 326: * is requested. 327: */ 328: public Accessible getAccessibleChild(JComponent c, int i) 329: { 330: return c.getAccessibleContext().getAccessibleChild(i); 331: } 332: }