--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/javax/swing/Autoscroller.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,179 @@
+/*
+ * Copyright 1997-2006 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package javax.swing;
+
+import java.awt.*;
+import java.awt.event.*;
+
+/**
+ * Autoscroller is responsible for generating synthetic mouse dragged
+ * events. It is the responsibility of the Component (or its MouseListeners)
+ * that receive the events to do the actual scrolling in response to the
+ * mouse dragged events.
+ *
+ * @author Dave Moore
+ * @author Scott Violet
+ */
+class Autoscroller implements ActionListener {
+    /**
+     * Global Autoscroller.
+     */
+    private static Autoscroller sharedInstance = new Autoscroller();
+
+    // As there can only ever be one autoscroller active these fields are
+    // static. The Timer is recreated as necessary to target the appropriate
+    // Autoscroller instance.
+    private static MouseEvent event;
+    private static Timer timer;
+    private static JComponent component;
+
+    //
+    // The public API, all methods are cover methods for an instance method
+    //
+    /**
+     * Stops autoscroll events from happening on the specified component.
+     */
+    public static void stop(JComponent c) {
+        sharedInstance._stop(c);
+    }
+
+    /**
+     * Stops autoscroll events from happening on the specified component.
+     */
+    public static boolean isRunning(JComponent c) {
+        return sharedInstance._isRunning(c);
+    }
+
+    /**
+     * Invoked when a mouse dragged event occurs, will start the autoscroller
+     * if necessary.
+     */
+    public static void processMouseDragged(MouseEvent e) {
+        sharedInstance._processMouseDragged(e);
+    }
+
+
+    Autoscroller() {
+    }
+
+    /**
+     * Starts the timer targeting the passed in component.
+     */
+    private void start(JComponent c, MouseEvent e) {
+        Point screenLocation = c.getLocationOnScreen();
+
+        if (component != c) {
+            _stop(component);
+        }
+        component = c;
+        event = new MouseEvent(component, e.getID(), e.getWhen(),
+                               e.getModifiers(), e.getX() + screenLocation.x,
+                               e.getY() + screenLocation.y,
+                               e.getXOnScreen(),
+                               e.getYOnScreen(),
+                               e.getClickCount(), e.isPopupTrigger(),
+                               MouseEvent.NOBUTTON);
+
+        if (timer == null) {
+            timer = new Timer(100, this);
+        }
+
+        if (!timer.isRunning()) {
+            timer.start();
+        }
+    }
+
+    //
+    // Methods mirror the public static API
+    //
+
+    /**
+     * Stops scrolling for the passed in widget.
+     */
+    private void _stop(JComponent c) {
+        if (component == c) {
+            if (timer != null) {
+                timer.stop();
+            }
+            timer = null;
+            event = null;
+            component = null;
+        }
+    }
+
+    /**
+     * Returns true if autoscrolling is currently running for the specified
+     * widget.
+     */
+    private boolean _isRunning(JComponent c) {
+        return (c == component && timer != null && timer.isRunning());
+    }
+
+    /**
+     * MouseListener method, invokes start/stop as necessary.
+     */
+    private void _processMouseDragged(MouseEvent e) {
+        JComponent component = (JComponent)e.getComponent();
+        boolean stop = true;
+        if (component.isShowing()) {
+            Rectangle visibleRect = component.getVisibleRect();
+            stop = visibleRect.contains(e.getX(), e.getY());
+        }
+        if (stop) {
+            _stop(component);
+        } else {
+            start(component, e);
+        }
+    }
+
+    //
+    // ActionListener
+    //
+    /**
+     * ActionListener method. Invoked when the Timer fires. This will scroll
+     * if necessary.
+     */
+    public void actionPerformed(ActionEvent x) {
+        JComponent component = Autoscroller.component;
+
+        if (component == null || !component.isShowing() || (event == null)) {
+            _stop(component);
+            return;
+        }
+        Point screenLocation = component.getLocationOnScreen();
+        MouseEvent e = new MouseEvent(component, event.getID(),
+                                      event.getWhen(), event.getModifiers(),
+                                      event.getX() - screenLocation.x,
+                                      event.getY() - screenLocation.y,
+                                      event.getXOnScreen(),
+                                      event.getYOnScreen(),
+                                      event.getClickCount(),
+                                      event.isPopupTrigger(),
+                                      MouseEvent.NOBUTTON);
+        component.superProcessMouseMotionEvent(e);
+    }
+
+}