LookAndFeel.java

/* LookAndFeel.java --
   Copyright (C) 2002, 2004, 2005, 2006,  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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permission to link this library with independent modules to produce an
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package javax.swing;

import java.awt.Color;
import java.awt.Component;
import java.awt.Font;
import java.awt.Toolkit;
import java.net.URL;

import javax.swing.border.Border;
import javax.swing.plaf.ComponentInputMapUIResource;
import javax.swing.plaf.IconUIResource;
import javax.swing.plaf.InputMapUIResource;
import javax.swing.plaf.UIResource;
import javax.swing.plaf.metal.MetalLookAndFeel;
import javax.swing.text.JTextComponent;

/**
 * A <i>look-and-feel</i> controls most aspects of the appearance and
 * operation of user interface components in <code>javax.swing</code>.  A
 * cross-platform look-and-feel (the {@link MetalLookAndFeel}) is provided.
 *
 * @see UIManager#getInstalledLookAndFeels()
 * @see UIManager#setLookAndFeel(LookAndFeel)
 */
public abstract class LookAndFeel
{
  /**
   * Creates and returns a look-and-feel specific defaults table.  This method
   * is called once by {@link UIManager#setLookAndFeel(LookAndFeel)} and
   * shouldn't be called again (as it creates a large table of defaults).
   *
   * @return The UI defaults.
   */
  public UIDefaults getDefaults()
  {
    return null;
  }

  /**
   * Returns a description of the look and feel.
   *
   * @return A description of the look and feel.
   */
  public abstract String getDescription();

  /**
   * Returns the value of <code>Toolkit.getDefaultToolkit()
   * .getDesktopProperty(systemPropertyName)</code>, or
   * <code>fallbackValue</code> if no such property is defined.
   *
   * @param systemPropertyName  the system property name.
   * @param fallbackValue  the fallback value.
   *
   * @return The property value or <code>fallbackValue</code>.
   */
  public static Object getDesktopPropertyValue(String systemPropertyName,
      Object fallbackValue)
  {
    Object value = Toolkit.getDefaultToolkit().getDesktopProperty(
        systemPropertyName);
    return value != null ? value : fallbackValue;
  }

  /**
   * Returns an identifier for the look and feel.
   *
   * @return An identifier for the look and feel.
   */
  public abstract String getID();

  /**
   * Returns the name for the look and feel.
   *
   * @return The name for the look and feel.
   */
  public abstract String getName();

  /**
   * Returns <code>true</code> when the look-and-feel supports window
   * decorations, and <code>false</code> otherwise. This default implementation
   * always returns <code>false</code> and needs to be overridden when the
   * derived look-and-feel supports this.
   *
   * @return <code>false</code>.
   *
   * @since 1.4
   */
  public boolean getSupportsWindowDecorations()
  {
    return false;
  }

  /**
   * Initializes the look-and-feel.  The
   * {@link UIManager#setLookAndFeel(LookAndFeel)} method calls this method
   * before the first call (and typically the only call) to
   * {@link #getDefaults()}.  This default implementation does nothing, but
   * subclasses can override this behaviour.
   */
  public void initialize()
  {
    // We do nothing here. This method is meant to be overridden by
    // LookAndFeel implementations.
  }

  /**
   * Convenience method for installing a component's default {@link Border}
   * object on the specified component if either the border is currently
   * <code>null</code> or already an instance of {@link UIResource}.
   *
   * @param c  the component (<code>null</code> not permitted).
   * @param defaultBorderName  the border name (for lookup in the UIDefaults
   *     table).
   */
  public static void installBorder(JComponent c, String defaultBorderName)
  {
    Border b = c.getBorder();
    if (b == null || b instanceof UIResource)
      c.setBorder(UIManager.getBorder(defaultBorderName));
  }

  /**
   * Convenience method for initializing a component's foreground and
   * background color properties with values from the current defaults table.
   *
   * @param c  the component (<code>null</code> not permitted).
   * @param defaultBgName  the key for the background color in the UIDefaults
   *     table.
   * @param defaultFgName  the key for the foreground color in the UIDefaults
   *     table.
   */
  public static void installColors(JComponent c, String defaultBgName,
                                   String defaultFgName)
  {
    // Install background.
    Color bg = c.getBackground();
    if (bg == null || bg instanceof UIResource)
      c.setBackground(UIManager.getColor(defaultBgName));

    // Install foreground.
    Color fg = c.getForeground();
    if (fg == null || fg instanceof UIResource)
      c.setForeground(UIManager.getColor(defaultFgName));
  }

  /**
   * Convenience method for initializing a component's foreground, background
   * and font properties with values from the current defaults table.
   *
   * @param component  the component (<code>null</code> not permitted).
   * @param defaultBgName  the key for the background color in the UIDefaults
   *     table.
   * @param defaultFgName  the key for the foreground color in the UIDefaults
   *     table.
   * @param defaultFontName  the key for the font in the UIDefaults table.
   */
  public static void installColorsAndFont(JComponent component,
                                          String defaultBgName,
                                          String defaultFgName,
                                          String defaultFontName)
  {
    // Install colors.
    installColors(component, defaultBgName, defaultFgName);
    // Install font.
    Font f = component.getFont();
    if (f == null || f instanceof UIResource)
      component.setFont(UIManager.getFont(defaultFontName));
  }

  /**
   * Returns <code>true</code> if the look-and-feel is the "native"
   * look-and-feel for the current platform, and <code>false</code> otherwise.
   * A native look-and-feel emulates the appearance and behaviour of the
   * default windowing system on the host operating system.
   *
   * @return A flag indicating whether or not this is the native look and feel
   *         for the current platform.
   */
  public abstract boolean isNativeLookAndFeel();

  /**
   * Returns <code>true</code> if the look-and-feel is supported on the
   * current operating system, and <code>false</code> otherwise.  This
   * mechanism is provided so that it is possible to prevent a look-and-feel
   * from being used on some operating systems (usually for legal, not
   * technical, reasons).
   *
   * @return A flag indicating whether or not the look-and-feel is supported
   *         on the current platform.
   */
  public abstract boolean isSupportedLookAndFeel();

  /**
   * Loads the bindings in keys into retMap. Does not remove existing entries
   * from retMap.  <code>keys</code> describes the InputMap, every even indexed
   * item is either a KeyStroke or a String representing a KeyStroke and every
   * odd indexed item is the Object associated with that KeyStroke in an
   * ActionMap.
   *
   * @param retMap the InputMap into which we load bindings
   * @param keys the Object array describing the InputMap as above
   */
  public static void loadKeyBindings(InputMap retMap, Object[] keys)
  {
    if (keys == null)
      return;
    for (int i = 0; i < keys.length - 1; i += 2)
      {
        Object key = keys[i];
        KeyStroke keyStroke;
        if (key instanceof KeyStroke)
          keyStroke = (KeyStroke) key;
        else
          keyStroke = KeyStroke.getKeyStroke((String) key);
        retMap.put(keyStroke, keys[i + 1]);
      }
  }

  /**
   * Creates a ComponentInputMap from keys.
   * <code>keys</code> describes the InputMap, every even indexed
   * item is either a KeyStroke or a String representing a KeyStroke and every
   * odd indexed item is the Object associated with that KeyStroke in an
   * ActionMap.
   *
   * @param c the JComponent associated with the ComponentInputMap
   * @param keys the Object array describing the InputMap as above
   *
   * @return A new input map.
   */
  public static ComponentInputMap makeComponentInputMap(JComponent c,
                                                        Object[] keys)
  {
    ComponentInputMap retMap = new ComponentInputMapUIResource(c);
    loadKeyBindings(retMap, keys);
    return retMap;
  }

  /**
   * Utility method that creates a UIDefaults.LazyValue that creates an
   * ImageIcon UIResource for the specified gifFile filename.
   *
   * @param baseClass  the base class for accessing the icon resource.
   * @param gifFile  the file name.
   *
   * @return A {@link UIDefaults.LazyValue} that serves up an
   *     {@link IconUIResource}.
   */
  public static Object makeIcon(Class<?> baseClass, String gifFile)
  {
    final URL file = baseClass.getResource(gifFile);
    return new UIDefaults.LazyValue()
      {
        public Object createValue(UIDefaults table)
        {
          return new IconUIResource(new ImageIcon(file));
        }
      };
  }

  /**
   * Creates a InputMap from keys.
   * <code>keys</code> describes the InputMap, every even indexed
   * item is either a KeyStroke or a String representing a KeyStroke and every
   * odd indexed item is the Object associated with that KeyStroke in an
   * ActionMap.
   *
   * @param keys the Object array describing the InputMap as above
   *
   * @return A new input map.
   */
  public static InputMap makeInputMap(Object[] keys)
  {
    InputMap retMap = new InputMapUIResource();
    loadKeyBindings(retMap, keys);
    return retMap;
  }

  /**
   * Convenience method for building lists of KeyBindings.
   * <code>keyBindingList</code> is an array of KeyStroke-Action pairs where
   * even indexed elements are KeyStrokes or Strings representing KeyStrokes
   * and odd indexed elements are the associated Actions.
   *
   * @param keyBindingList the array of KeyStroke-Action pairs
   * @return a JTextComponent.KeyBinding array
   */
  public static JTextComponent.KeyBinding[] makeKeyBindings(
      Object[] keyBindingList)
  {
    JTextComponent.KeyBinding[] retBindings =
      new JTextComponent.KeyBinding[keyBindingList.length / 2];
    for (int i = 0; i < keyBindingList.length - 1; i += 2)
      {
        KeyStroke stroke;
        if (keyBindingList[i] instanceof KeyStroke)
          stroke = (KeyStroke) keyBindingList[i];
        else
          stroke = KeyStroke.getKeyStroke((String) keyBindingList[i]);
        retBindings[i / 2] = new JTextComponent.KeyBinding(stroke,
            (String) keyBindingList[i + 1]);
      }
    return retBindings;
  }

  /**
   * Invoked when the user attempts an invalid operation. The default
   * implementation just beeps. Subclasses that wish to change this need to
   * override this method.
   *
   * @param component the component the error occured in
   */
  public void provideErrorFeedback(Component component)
  {
    Toolkit.getDefaultToolkit().beep();
  }

  /**
   * Returns a string that displays and identifies this object's properties.
   *
   * @return string containing the description and class name.
   */
  public String toString()
  {
    return getDescription() + " " + getClass().getName();
  }

  /**
   * UIManager.setLookAndFeel calls this method just before we're replaced by
   * a new default look and feel.
   */
  public void uninitialize()
  {
    // We do nothing here. This method is meant to be overridden by
    // LookAndFeel implementations.
  }

  /**
   * Convenience method for un-installing a component's default border on the
   * specified component if the border is currently an instance of UIResource.
   *
   * @param c  the component (<code>null</code> not permitted).
   */
  public static void uninstallBorder(JComponent c)
  {
    if (c.getBorder() instanceof UIResource)
      c.setBorder(null);
  }

  /**
   * This methods installs a UI property if it hasn't already been set by an
   * application. This method is used by UI delegates that install a default
   * value for a property with a primitive type but do not want to override
   * a value that has been set by an application.
   *
   * The supported properties depend on the actual type of the component and
   * are listed in the table below. The supported properties are of course
   * inherited to subclasses.
   *
   * <table>
   * <tr><th>Type</th><th>Supported properties</th></tr>
   * <tr><td><code>JComponent</code></td>
   *     <td><code>opaque, autoscrolls</code></td></tr>
   * <tr><td><code>AbstractButton</code></td>
   *     <td><code>borderPainted, rolloverEnabled, iconTextGap,
   *      contentAreaFilled</code></td></tr>
   * <tr><td><code>JDesktopPane</code></td>
   *     <td><code>dragMode</code></td></tr>
   * <tr><td><code>JSplitPane</code></td>
   *     <td><code>dividerSize, oneTouchExpandable</code></td></tr>
   * <tr><td><code>JTable</code></td>
   *     <td><code>rowHeight</code></td></tr>
   * <tr><td><code>JTree</code></td>
   *     <td><code>rowHeight, scrollsOnExpand, showsRootHandles</code></td></tr>
   * </table>
   *
   * @param c the component to install the property to
   * @param propertyName the name of the property
   * @param value the value of the property
   *
   * @throws IllegalArgumentException if the specified property cannot be set
   *         by this method
   * @throws ClassCastException if the property value does not match the
   *         property type
   * @throws NullPointerException if <code>c</code> or
   *         <code>propertyValue</code> is <code>null</code>
   *
   * @since 1.5
   */
  public static void installProperty(JComponent c, String propertyName,
                                     Object value)
  {
    c.setUIProperty(propertyName, value);
  }
}