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 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

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 */

package java.awt;

import java.util.Vector;

import java.awt.peer.SystemTrayPeer;

import java.beans.PropertyChangeListener;

import java.beans.PropertyChangeSupport;

import sun.awt.AppContext;

import sun.awt.SunToolkit;

import sun.awt.HeadlessToolkit;

import sun.security.util.SecurityConstants;

/**

 * The <code>SystemTray</code> class represents the system tray for a

 * desktop.  On Microsoft Windows it is referred to as the "Taskbar

 * Status Area", on Gnome it is referred to as the "Notification

 * Area", on KDE it is referred to as the "System Tray".  The system

 * tray is shared by all applications running on the desktop.

 *

 * <p> On some platforms the system tray may not be present or may not

 * be supported, in this case {@link SystemTray#getSystemTray()}

 * throws {@link UnsupportedOperationException}.  To detect whether the

 * system tray is supported, use {@link SystemTray#isSupported}.

 *

 * <p>The <code>SystemTray</code> may contain one or more {@link

 * TrayIcon TrayIcons}, which are added to the tray using the {@link

 * #add} method, and removed when no longer needed, using the

 * {@link #remove}.  <code>TrayIcon</code> consists of an

 * image, a popup menu and a set of associated listeners.  Please see

 * the {@link TrayIcon} class for details.

 *

 * <p>Every Java application has a single <code>SystemTray</code>

 * instance that allows the app to interface with the system tray of

 * the desktop while the app is running.  The <code>SystemTray</code>

 * instance can be obtained from the {@link #getSystemTray} method.

 * An application may not create its own instance of

 * <code>SystemTray</code>.

 *

 * <p>The following code snippet demonstrates how to access

 * and customize the system tray:

 * <code>

 * <pre>

 *     {@link TrayIcon} trayIcon = null;

 *     if (SystemTray.isSupported()) {

 *         // get the SystemTray instance

 *         SystemTray tray = SystemTray.{@link #getSystemTray};

 *         // load an image

 *         {@link java.awt.Image} image = {@link java.awt.Toolkit#getImage(String) Toolkit.getDefaultToolkit().getImage}(...);

 *         // create a action listener to listen for default action executed on the tray icon

 *         {@link java.awt.event.ActionListener} listener = new {@link java.awt.event.ActionListener ActionListener}() {

 *             public void {@link java.awt.event.ActionListener#actionPerformed actionPerformed}({@link java.awt.event.ActionEvent} e) {

 *                 // execute default action of the application

 *                 // ...

 *             }

 *         };

 *         // create a popup menu

 *         {@link java.awt.PopupMenu} popup = new {@link java.awt.PopupMenu#PopupMenu PopupMenu}();

 *         // create menu item for the default action

 *         MenuItem defaultItem = new MenuItem(...);

 *         defaultItem.addActionListener(listener);

 *         popup.add(defaultItem);

 *         /// ... add other items

 *         // construct a TrayIcon

 *         trayIcon = new {@link TrayIcon#TrayIcon(java.awt.Image, String, java.awt.PopupMenu) TrayIcon}(image, "Tray Demo", popup);

 *         // set the TrayIcon properties

 *         trayIcon.{@link TrayIcon#addActionListener(java.awt.event.ActionListener) addActionListener}(listener);

 *         // ...

 *         // add the tray image

 *         try {

 *             tray.{@link SystemTray#add(TrayIcon) add}(trayIcon);

 *         } catch (AWTException e) {

 *             System.err.println(e);

 *         }

 *         // ...

 *     } else {

 *         // disable tray option in your application or

 *         // perform other actions

 *         ...

 *     }

 *     // ...

 *     // some time later

 *     // the application state has changed - update the image

 *     if (trayIcon != null) {

 *         trayIcon.{@link TrayIcon#setImage(java.awt.Image) setImage}(updatedImage);

 *     }

 *     // ...

 * </pre>

 * </code>

 *

 * @since 1.6

 * @see TrayIcon

 *

 * @author Bino George

 * @author Denis Mikhalkin

 * @author Sharon Zakhour

 * @author Anton Tarasov

 */

public class SystemTray {

    private static SystemTray systemTray;

    private int currentIconID = 0; // each TrayIcon added gets a unique ID

    transient private SystemTrayPeer peer;

    private static final TrayIcon[] EMPTY_TRAY_ARRAY = new TrayIcon[0];

    /**

     * Private <code>SystemTray</code> constructor.

     *

     */

    private SystemTray() {

        addNotify();

    }

    /**

     * Gets the <code>SystemTray</code> instance that represents the

     * desktop's tray area.  This always returns the same instance per

     * application.  On some platforms the system tray may not be

     * supported.  You may use the {@link #isSupported} method to

     * check if the system tray is supported.

     *

     * <p>If a SecurityManager is installed, the AWTPermission

     * {@code accessSystemTray} must be granted in order to get the

     * {@code SystemTray} instance. Otherwise this method will throw a

     * SecurityException.

     *

     * @return the <code>SystemTray</code> instance that represents

     * the desktop's tray area

     * @throws UnsupportedOperationException if the system tray isn't

     * supported by the current platform

     * @throws HeadlessException if

     * <code>GraphicsEnvironment.isHeadless()</code> returns <code>true</code>

     * @throws SecurityException if {@code accessSystemTray} permission

     * is not granted

     * @see #add(TrayIcon)

     * @see TrayIcon

     * @see #isSupported

     * @see SecurityManager#checkPermission

     * @see AWTPermission

     */

    public static SystemTray getSystemTray() {

        checkSystemTrayAllowed();

        if (GraphicsEnvironment.isHeadless()) {

            throw new HeadlessException();

        }

        initializeSystemTrayIfNeeded();

        if (!isSupported()) {

            throw new UnsupportedOperationException(

                "The system tray is not supported on the current platform.");

        }

        return systemTray;

    }

    /**

     * Returns whether the system tray is supported on the current

     * platform.  In addition to displaying the tray icon, minimal

     * system tray support includes either a popup menu (see {@link

     * TrayIcon#setPopupMenu(PopupMenu)}) or an action event (see

     * {@link TrayIcon#addActionListener(ActionListener)}).

     *

     * <p>Developers should not assume that all of the system tray

     * functionality is supported.  To guarantee that the tray icon's

     * default action is always accessible, add the default action to

     * both the action listener and the popup menu.  See the {@link

     * SystemTray example} for an example of how to do this.

     *

     * <p><b>Note</b>: When implementing <code>SystemTray</code> and

     * <code>TrayIcon</code> it is <em>strongly recommended</em> that

     * you assign different gestures to the popup menu and an action

     * event.  Overloading a gesture for both purposes is confusing

     * and may prevent the user from accessing one or the other.

     *

     * @see #getSystemTray

     * @return <code>false</code> if no system tray access is supported; this

     * method returns <code>true</code> if the minimal system tray access is

     * supported but does not guarantee that all system tray

     * functionality is supported for the current platform

     */

    public static boolean isSupported() {

        Toolkit toolkit = Toolkit.getDefaultToolkit();

        if (toolkit instanceof SunToolkit) {

            return ((SunToolkit)toolkit).isTraySupported();

        } else if (toolkit instanceof HeadlessToolkit) {

            return ((HeadlessToolkit)toolkit).isTraySupported();

        }

    }

    /**

     * Adds a <code>TrayIcon</code> to the <code>SystemTray</code>.

     * The tray icon becomes visible in the system tray once it is

     * added.  The order in which icons are displayed in a tray is not

     * specified - it is platform and implementation-dependent.

     *

     * <p> All icons added by the application are automatically

     * removed from the <code>SystemTray</code> upon application exit

     * and also when the desktop system tray becomes unavailable.

     *

     * @param trayIcon the <code>TrayIcon</code> to be added

     * @throws NullPointerException if <code>trayIcon</code> is

     * <code>null</code>

     * @throws IllegalArgumentException if the same instance of

     * a <code>TrayIcon</code> is added more than once

     * @throws AWTException if the desktop system tray is missing

     * @see #remove(TrayIcon)

     * @see #getSystemTray

     * @see TrayIcon

     * @see java.awt.Image

     */

    public void add(TrayIcon trayIcon) throws AWTException {

        if (trayIcon == null) {

            throw new NullPointerException("adding null TrayIcon");

        }

        TrayIcon[] oldArray = null, newArray = null;

        Vector<TrayIcon> icons = null;

        synchronized (this) {

            oldArray = systemTray.getTrayIcons();

            icons = (Vector<TrayIcon>)AppContext.getAppContext().get(TrayIcon.class);

            if (icons == null) {

                icons = new Vector<TrayIcon>(3);

                AppContext.getAppContext().put(TrayIcon.class, icons);

            } else if (icons.contains(trayIcon)) {

                throw new IllegalArgumentException("adding TrayIcon that is already added");

            }

            icons.add(trayIcon);

            newArray = systemTray.getTrayIcons();

            trayIcon.setID(++currentIconID);

        }

        try {

            trayIcon.addNotify();

        } catch (AWTException e) {

            icons.remove(trayIcon);

            throw e;

        }

        firePropertyChange("trayIcons", oldArray, newArray);

    }

    /**

     * Removes the specified <code>TrayIcon</code> from the

     * <code>SystemTray</code>.

     *

     * <p> All icons added by the application are automatically

     * removed from the <code>SystemTray</code> upon application exit

     * and also when the desktop system tray becomes unavailable.

     *

     * <p> If <code>trayIcon</code> is <code>null</code> or was not

     * added to the system tray, no exception is thrown and no action

     * is performed.

     *

     * @param trayIcon the <code>TrayIcon</code> to be removed

     * @see #add(TrayIcon)

     * @see TrayIcon

     */

    public void remove(TrayIcon trayIcon) {

        if (trayIcon == null) {

            return;

        }

        TrayIcon[] oldArray = null, newArray = null;

        synchronized (this) {

            oldArray = systemTray.getTrayIcons();

            Vector<TrayIcon> icons = (Vector<TrayIcon>)AppContext.getAppContext().get(TrayIcon.class);

            // TrayIcon with no peer is not contained in the array.

            if (icons == null || !icons.remove(trayIcon)) {

                return;

            }

            trayIcon.removeNotify();

            newArray = systemTray.getTrayIcons();

        }

        firePropertyChange("trayIcons", oldArray, newArray);

    }

    /**

     * Returns an array of all icons added to the tray by this

     * application.  You can't access the icons added by another

     * application.  Some browsers partition applets in different

     * code bases into separate contexts, and establish walls between

     * these contexts.  In such a scenario, only the tray icons added

     * from this context will be returned.

     *

     * <p> The returned array is a copy of the actual array and may be

     * modified in any way without affecting the system tray.  To

     * remove a <code>TrayIcon</code> from the

     * <code>SystemTray</code>, use the {@link

     * #remove(TrayIcon)} method.

     *

     * @return an array of all tray icons added to this tray, or an

     * empty array if none has been added

     * @see #add(TrayIcon)

     * @see TrayIcon

     */

    public TrayIcon[] getTrayIcons() {

        Vector<TrayIcon> icons = (Vector<TrayIcon>)AppContext.getAppContext().get(TrayIcon.class);

        if (icons != null) {

            return (TrayIcon[])icons.toArray(new TrayIcon[icons.size()]);

        }

        return EMPTY_TRAY_ARRAY;

    }

    /**

     * Returns the size, in pixels, of the space that a tray icon will

     * occupy in the system tray.  Developers may use this methods to

     * acquire the preferred size for the image property of a tray icon

     * before it is created.  For convenience, there is a similar

     * method {@link TrayIcon#getSize} in the <code>TrayIcon</code> class.

     *

     * @return the default size of a tray icon, in pixels

     * @see TrayIcon#setImageAutoSize(boolean)

     * @see java.awt.Image

     * @see TrayIcon#getSize()

     */

    public Dimension getTrayIconSize() {

        return peer.getTrayIconSize();

    }

    /**

     * Adds a {@code PropertyChangeListener} to the list of listeners for the

     * specific property. The following properties are currently supported:

     * <p> </p>

     * <table border=1 summary="SystemTray properties">

     * <tr>

     *    <th>Property</th>

     *    <th>Description</th>

     * </tr>

     * <tr>

     *    <td>{@code trayIcons}</td>

     *    <td>The {@code SystemTray}'s array of {@code TrayIcon} objects.

     *        The array is accessed via the {@link #getTrayIcons} method.<br>

     *        This property is changed when a tray icon is added to (or removed

     *        from) the system tray.<br> For example, this property is changed

     *        when the system tray becomes unavailable on the desktop<br>

     *        and the tray icons are automatically removed.</td>

     * </tr>

     * <tr>

     *    <td>{@code systemTray}</td>

     *    <td>This property contains {@code SystemTray} instance when the system tray

     *        is available or <code>null</code> otherwise.<br> This property is changed

     *        when the system tray becomes available or unavailable on the desktop.<br>

     *        The property is accessed by the {@link #getSystemTray} method.</td>

     * </tr>

     * </table>

     * <p> </p>

     * The {@code listener} listens to property changes only in this context.

     * <p>

     * If {@code listener} is {@code null}, no exception is thrown

     * and no action is performed.

     *

     * @param propertyName the specified property

     * @param listener the property change listener to be added

     *

     * @see #removePropertyChangeListener

     * @see #getPropertyChangeListeners

     */

    public synchronized void addPropertyChangeListener(String propertyName,

                                                       PropertyChangeListener listener)

    {

        if (listener == null) {

            return;

        }

        getCurrentChangeSupport().addPropertyChangeListener(propertyName, listener);

    }

    /**

     * Removes a {@code PropertyChangeListener} from the listener list

     * for a specific property.

     * <p>

     * The {@code PropertyChangeListener} must be from this context.

     * <p>

     * If {@code propertyName} or {@code listener} is {@code null} or invalid,

     * no exception is thrown and no action is taken.

     *

     * @param propertyName the specified property

     * @param listener the PropertyChangeListener to be removed

     *

     * @see #addPropertyChangeListener

     * @see #getPropertyChangeListeners

     */

    public synchronized void removePropertyChangeListener(String propertyName,

                                                          PropertyChangeListener listener)

    {

        if (listener == null) {

            return;

        }

        getCurrentChangeSupport().removePropertyChangeListener(propertyName, listener);

    }

    /**

     * Returns an array of all the listeners that have been associated

     * with the named property.

     * <p>

     * Only the listeners in this context are returned.

     *

     * @param propertyName the specified property

     * @return all of the {@code PropertyChangeListener}s associated with

     *         the named property; if no such listeners have been added or

     *         if {@code propertyName} is {@code null} or invalid, an empty

     *         array is returned

     *

     * @see #addPropertyChangeListener

     * @see #removePropertyChangeListener

     */

    public synchronized PropertyChangeListener[] getPropertyChangeListeners(String propertyName) {

        return getCurrentChangeSupport().getPropertyChangeListeners(propertyName);

    }

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

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

    /**

     * Support for reporting bound property changes for Object properties.

     * This method can be called when a bound property has changed and it will

     * send the appropriate PropertyChangeEvent to any registered

     * PropertyChangeListeners.

     *

     * @param propertyName the property whose value has changed

     * @param oldValue the property's previous value

     * @param newValue the property's new value

     */

    private void firePropertyChange(String propertyName,

                                    Object oldValue, Object newValue)

    {

        if (oldValue != null && newValue != null && oldValue.equals(newValue)) {

            return;

        }

        getCurrentChangeSupport().firePropertyChange(propertyName, oldValue, newValue);

    }

    /**

     * Returns the current PropertyChangeSupport instance for the

     * calling thread's context.

     *

     * @return this thread's context's PropertyChangeSupport

     */

    private synchronized PropertyChangeSupport getCurrentChangeSupport() {

        PropertyChangeSupport changeSupport =

            (PropertyChangeSupport)AppContext.getAppContext().get(SystemTray.class);

        if (changeSupport == null) {

            changeSupport = new PropertyChangeSupport(this);

            AppContext.getAppContext().put(SystemTray.class, changeSupport);

        }

        return changeSupport;

    }

    synchronized void addNotify() {

        if (peer == null) {

        }

    }

    static void checkSystemTrayAllowed() {

        SecurityManager security = System.getSecurityManager();

        if (security != null) {

            security.checkPermission(SecurityConstants.ACCESS_SYSTEM_TRAY_PERMISSION);

        }

    }

    private static void initializeSystemTrayIfNeeded() {

        synchronized (SystemTray.class) {

            if (systemTray == null) {

                systemTray = new SystemTray();

            }

        }

    }

}