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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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.
 *
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package sun.awt;

import java.awt.*;
import java.awt.event.InputEvent;
import java.awt.event.InvocationEvent;

A stateless class which responds to native mouse moves, Component resizes,
Component moves, showing and hiding of Components, minimizing and
maximizing of top level Windows, addition and removal of Components,
and calls to setCursor().
/**
 * A stateless class which responds to native mouse moves, Component resizes,
 * Component moves, showing and hiding of Components, minimizing and
 * maximizing of top level Windows, addition and removal of Components,
 * and calls to setCursor().
 */
public abstract class GlobalCursorManager {

    class NativeUpdater implements Runnable {
        boolean pending = false;

        public void run() {
            boolean shouldUpdate = false;
            synchronized (this) {
                if (pending) {
                    pending = false;
                    shouldUpdate = true;
                }
            }
            if (shouldUpdate) {
                _updateCursor(false);
            }
        }

        public void postIfNotPending(Component heavy, InvocationEvent in) {
            boolean shouldPost = false;
            synchronized (this) {
                if (!pending) {
                    pending = shouldPost = true;
                }
            }
            if (shouldPost) {
                SunToolkit.postEvent(SunToolkit.targetToAppContext(heavy), in);
            }
        }
    }

    
Use a singleton NativeUpdater for better performance. We cannot use
a singleton InvocationEvent because we want each event to have a fresh
timestamp.
/**
     * Use a singleton NativeUpdater for better performance. We cannot use
     * a singleton InvocationEvent because we want each event to have a fresh
     * timestamp.
     */
    private final NativeUpdater nativeUpdater = new NativeUpdater();

    
The last time the cursor was updated, in milliseconds.
/**
     * The last time the cursor was updated, in milliseconds.
     */
    private long lastUpdateMillis;

    
Locking object for synchronizing access to lastUpdateMillis. The VM
does not guarantee atomicity of longs.
/**
     * Locking object for synchronizing access to lastUpdateMillis. The VM
     * does not guarantee atomicity of longs.
     */
    private final Object lastUpdateLock = new Object();

    
Should be called for any activity at the Java level which may affect
the global cursor, except for Java MOUSE_MOVED events.
/**
     * Should be called for any activity at the Java level which may affect
     * the global cursor, except for Java MOUSE_MOVED events.
     */
    public void updateCursorImmediately() {
        synchronized (nativeUpdater) {
            nativeUpdater.pending = false;
        }
        _updateCursor(false);
    }

    
Should be called in response to Java MOUSE_MOVED events. The update
will be discarded if the InputEvent is outdated.
Params:
e – the InputEvent which triggered the cursor update./**
     * Should be called in response to Java MOUSE_MOVED events. The update
     * will be discarded if the InputEvent is outdated.
     *
     * @param   e the InputEvent which triggered the cursor update.
     */
    public void updateCursorImmediately(InputEvent e) {
        boolean shouldUpdate;
        synchronized (lastUpdateLock) {
            shouldUpdate = (e.getWhen() >= lastUpdateMillis);
        }
        if (shouldUpdate) {
            _updateCursor(true);
        }
    }

    
Should be called in response to a native mouse enter or native mouse
button released message. Should not be called during a mouse drag.
/**
     * Should be called in response to a native mouse enter or native mouse
     * button released message. Should not be called during a mouse drag.
     */
    public void updateCursorLater(Component heavy) {
        nativeUpdater.postIfNotPending(heavy, new InvocationEvent
            (Toolkit.getDefaultToolkit(), nativeUpdater));
    }

    protected GlobalCursorManager() { }

    
Set the global cursor to the specified cursor. The component over
which the Cursor current resides is provided as a convenience. Not
all platforms may require the Component.
/**
     * Set the global cursor to the specified cursor. The component over
     * which the Cursor current resides is provided as a convenience. Not
     * all platforms may require the Component.
     */
    protected abstract void setCursor(Component comp, Cursor cursor,
                                      boolean useCache);
    
Returns the global cursor position, in screen coordinates.
/**
     * Returns the global cursor position, in screen coordinates.
     */
    protected abstract void getCursorPos(Point p);

    protected abstract Point getLocationOnScreen(Component com);

    
Returns the most specific, visible, heavyweight Component
under the cursor. This method should return null iff the cursor is
not over any Java Window.
Params:
useCache – If true, the implementation is free to use caching
mechanisms because the Z-order, visibility, and enabled state of the
Components has not changed. If false, the implementation should not
make these assumptions./**
     * Returns the most specific, visible, heavyweight Component
     * under the cursor. This method should return null iff the cursor is
     * not over any Java Window.
     *
     * @param   useCache If true, the implementation is free to use caching
     * mechanisms because the Z-order, visibility, and enabled state of the
     * Components has not changed. If false, the implementation should not
     * make these assumptions.
     */
    protected abstract Component findHeavyweightUnderCursor(boolean useCache);

    
Updates the global cursor. We apply a three-step scheme to cursor
updates:

(1) InputEvent updates which are outdated are discarded by
updateCursorImmediately(InputEvent).

(2) If 'useCache' is true, the native code is free to use a cached
value to determine the most specific, visible, enabled heavyweight
because this update is occurring in response to a mouse move. If
'useCache' is false, the native code must perform a new search given
the current mouse coordinates.
(3) Once we have determined the most specific, visible, enabled
heavyweight, we use findComponentAt to find the most specific, visible,
enabled Component.
/**
     * Updates the global cursor. We apply a three-step scheme to cursor
     * updates:<p>
     *
     * (1) InputEvent updates which are outdated are discarded by
     * <code>updateCursorImmediately(InputEvent)</code>.<p>
     *
     * (2) If 'useCache' is true, the native code is free to use a cached
     * value to determine the most specific, visible, enabled heavyweight
     * because this update is occurring in response to a mouse move. If
     * 'useCache' is false, the native code must perform a new search given
     * the current mouse coordinates.
     *
     * (3) Once we have determined the most specific, visible, enabled
     * heavyweight, we use findComponentAt to find the most specific, visible,
     * enabled Component.
     */
    private void _updateCursor(boolean useCache) {

        synchronized (lastUpdateLock) {
            lastUpdateMillis = System.currentTimeMillis();
        }

        Point queryPos = null, p = null;
        Component comp;

        try {
            comp = findHeavyweightUnderCursor(useCache);
            if (comp == null) {
                updateCursorOutOfJava();
                return;
            }

            if (comp instanceof Window) {
                p = AWTAccessor.getComponentAccessor().getLocation(comp);
            } else if (comp instanceof Container) {
                p = getLocationOnScreen(comp);
            }
            if (p != null) {
                queryPos = new Point();
                getCursorPos(queryPos);
                Component c = AWTAccessor.getContainerAccessor().
                        findComponentAt((Container) comp,
                        queryPos.x - p.x, queryPos.y - p.y, false);

                // If findComponentAt returns null, then something bad has
                // happened. For example, the heavyweight Component may
                // have been hidden or disabled by another thread. In that
                // case, we'll just use the originial heavyweight.
                if (c != null) {
                    comp = c;
                }
            }

            setCursor(comp, AWTAccessor.getComponentAccessor().getCursor(comp), useCache);

        } catch (IllegalComponentStateException e) {
            // Shouldn't happen, but if it does, abort.
        }
    }

    protected void updateCursorOutOfJava() {
        // Cursor is not over a Java Window. Do nothing...usually
        // But we need to update it in case of grab on X.
    }
}