javax/swing/LookAndFeel.java

/* LookAndFeel.java --
   Copyright (C) 2002, 2004, 2005  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.text.JTextComponent;

public abstract class LookAndFeel
{
  /**
   * This method is called once by UIManager.setLookAndFeel to create
   * the look and feel specific defaults table.
   *
   * @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();

  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 true when the Look and Feel supports window decorations,
   * false others. This method returns always false and needs to be overwritten
   * when the derived Look and Feel supports this.
   *
   * @return false
   *
   * @since 1.4
   */
  public boolean getSupportsWindowDecorations()
  {
    return false;
  }

  /**
   * UIManager.setLookAndFeel calls this method before the first call
   * (and typically the only call) to getDefaults().
   */
  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 Border object
   * on the specified component if either the border is currently null
   * or already an instance of UIResource.
   */
  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.
   */
  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 components foreground background
   * and font properties with values from the current defaults 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.
   *
   * @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
   */
  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.
   */
  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
   */
  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 implement
   * 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 the string "LookAndFeel"
   */
  public String toString()
  {
    return "LookAndFeel";
  }

  /**
   * 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.
   */
  public static void uninstallBorder(JComponent c)
  {
    if (c.getBorder() instanceof UIResource)
      c.setBorder(null);
  }
}