toolkit.java

gcc3.2.1源代码

/* Toolkit.java -- AWT Toolkit superclass
   Copyright (C) 1999, 2000, 2001, 2002 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
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package java.awt;

import java.awt.event.*;
import java.awt.peer.*;
import java.awt.image.*;
import java.awt.datatransfer.Clipboard;
import java.util.Properties;
import java.net.URL;
import java.beans.*;

/**
  * The AWT system uses a set of native peer objects to implement its
  * widgets.  These peers are provided by a peer toolkit, that is accessed
  * via a subclass of this superclass.  The system toolkit is retrieved
  * by the static methods <code>getDefaultToolkit</code>.  This method
  * determines the system toolkit by examining the system property
  * <code>awt.toolkit</code>.  That property is set to the name of the
  * <code>Toolkit</code> subclass for the specified peer set.  If the
  * <code>awt.toolkit</code> property is not set, then the default
  * toolkit <code>gnu.java.awt.peer.gtk.GtkToolkit</code> is used.  This
  * toolkit creates its peers using the GTK+ toolkit.
  *
  * @author Aaron M. Renn ([e-mail])
  */
public abstract class Toolkit
{

/*
 * Static Variables
 */

// The default toolkit name.
private static String default_toolkit_name = 
  "gnu.java.awt.peer.gtk.GtkToolkit";

// The toolkit in use.  Once we load it, we don't ever change it
// if the awt.toolkit propert is set.
private static Toolkit toolkit;

// The toolkit properties
private static Properties props = new Properties();

private PropertyChangeSupport changeSupport = new PropertyChangeSupport(this);

private Properties desktopProperties = new Properties();

/*************************************************************************/

/*
 * Static Methods
 */

/**
  * Returns an instance of the default toolkit.  The default toolkit is
  * the subclass of <code>Toolkit</code> specified in the system property
  * <code>awt.toolkit</code>, or <code>gnu.java.awt.peer.gtk.GtkToolkit</code>
  * if the property is not set.
  *
  * @return An instance of the system default toolkit.
  *
  * @error AWTError If the toolkit cannot be loaded.
  */
public static Toolkit
getDefaultToolkit()
{
  if (toolkit != null)
    return(toolkit);

  String toolkit_name = System.getProperty("awt.toolkit",
					   default_toolkit_name);

  try
    {
      Class cls = Class.forName(toolkit_name);
      Object obj = cls.newInstance();

      if (!(obj instanceof Toolkit))
        throw new AWTError(toolkit_name + " is not a subclass of " +
                           "java.awt.Toolkit");

      toolkit = (Toolkit)obj;
      return(toolkit);
    }
  catch(Exception e)
    {
      throw new AWTError("Cannot load AWT toolkit: " + e.getMessage());
    }
}

/*************************************************************************/

/**
  * Returns the value of the property with the specified name, or the
  * default value if the property does not exist.
  *
  * @param key The name of the property to retrieve.
  * @param defThe default value of the property.
  */
public static String
getProperty(String key, String def)
{
  return(props.getProperty(key, def));
}

/*************************************************************************/

/**
  * Returns the native container object of the specified component.  This
  * method is necessary because the parent component might be a lightweight
  * component.
  *
  * @param component The component to fetch the native container for.
  *
  * @return The native container object for this component.
  */
protected static Container
getNativeContainer(Component component)
{
  component = component.getParent();

  for(;;)
    {
      if (component == null)
        return(null);

      if (!(component instanceof Container))
        {
          component = component.getParent();
          continue;
        }

      if (component.getPeer() instanceof LightweightPeer)
        {
          component = component.getParent();
          continue;
        } 

      return((Container)component);
    }
}

/*************************************************************************/

/*
 * Constructors
 */

/**
  * Default constructor for subclasses.
  */
public
Toolkit()
{
}

/*************************************************************************/

/*
 * Instance Methods
 */

/**
  * Creates a peer object for the specified <code>Button</code>.
  *
  * @param target The <code>Button</code> to create the peer for.
  *
  * @return The peer for the specified <code>Button</code> object.
  */
protected abstract ButtonPeer
createButton(Button target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>TextField</code>.
  *
  * @param target The <code>TextField</code> to create the peer for.
  *
  * @return The peer for the specified <code>TextField</code> object.
  */
protected abstract TextFieldPeer
createTextField(TextField target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Label</code>.
  *
  * @param target The <code>Label</code> to create the peer for.
  *
  * @return The peer for the specified <code>Label</code> object.
  */
protected abstract LabelPeer
createLabel(Label target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>List</code>.
  *
  * @param target The <code>List</code> to create the peer for.
  *
  * @return The peer for the specified <code>List</code> object.
  */
protected abstract ListPeer
createList(List target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Checkbox</code>.
  *
  * @param target The <code>Checkbox</code> to create the peer for.
  *
  * @return The peer for the specified <code>Checkbox</code> object.
  */
protected abstract CheckboxPeer
createCheckbox(Checkbox target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Scrollbar</code>.
  *
  * @param target The <code>Scrollbar</code> to create the peer for.
  *
  * @return The peer for the specified <code>Scrollbar</code> object.
  */
protected abstract ScrollbarPeer
createScrollbar(Scrollbar target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>ScrollPane</code>.
  *
  * @param target The <code>ScrollPane</code> to create the peer for.
  *
  * @return The peer for the specified <code>ScrollPane</code> object.
  */
protected abstract ScrollPanePeer
createScrollPane(ScrollPane target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>TextArea</code>.
  *
  * @param target The <code>TextArea</code> to create the peer for.
  *
  * @return The peer for the specified <code>TextArea</code> object.
  */
protected abstract TextAreaPeer
createTextArea(TextArea target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Choice</code>.
  *
  * @param target The <code>Choice</code> to create the peer for.
  *
  * @return The peer for the specified <code>Choice</code> object.
  */
protected abstract ChoicePeer
createChoice(Choice target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Frame</code>.
  *
  * @param target The <code>Frame</code> to create the peer for.
  *
  * @return The peer for the specified <code>Frame</code> object.
  */
protected abstract FramePeer
createFrame(Frame target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Canvas</code>.
  *
  * @param target The <code>Canvas</code> to create the peer for.
  *
  * @return The peer for the specified <code>Canvas</code> object.
  */
protected abstract CanvasPeer
createCanvas(Canvas target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Panel</code>.
  *
  * @param target The <code>Panel</code> to create the peer for.
  *
  * @return The peer for the specified <code>Panel</code> object.
  */
protected abstract PanelPeer
createPanel(Panel target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Window</code>.
  *
  * @param target The <code>Window</code> to create the peer for.
  *
  * @return The peer for the specified <code>Window</code> object.
  */
protected abstract WindowPeer
createWindow(Window target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Dialog</code>.
  *
  * @param target The dialog to create the peer for
  *
  * @return The peer for the specified font name.
  */
protected abstract DialogPeer
createDialog(Dialog target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>MenuBar</code>.
  *
  * @param target The <code>MenuBar</code> to create the peer for.
  *
  * @return The peer for the specified <code>MenuBar</code> object.
  */
protected abstract MenuBarPeer
createMenuBar(MenuBar target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>Menu</code>.
  *
  * @param target The <code>Menu</code> to create the peer for.
  *
  * @return The peer for the specified <code>Menu</code> object.
  */
protected abstract MenuPeer
createMenu(Menu target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>PopupMenu</code>.
  *
  * @param target The <code>PopupMenu</code> to create the peer for.
  *
  * @return The peer for the specified <code>PopupMenu</code> object.
  */
protected abstract PopupMenuPeer
createPopupMenu(PopupMenu target);

/*************************************************************************/

/**
  * Creates a peer object for the specified <code>MenuItem</code>.
  *
  * @param target The <code>MenuItem</code> to create the peer for.
  *
  * @return The peer for the specified <code>MenuItem</code> object.
  */
protected abstract MenuItemPeer
createMenuItem(MenuItem target);