MyOtherDropTarget.java

package aliview.sequencelist;

import java.awt.Component;
import java.awt.Dimension;
import java.awt.Insets;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.dnd.Autoscroll;
import java.awt.dnd.DropTarget;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.Timer;

public class MyOtherDropTarget extends DropTarget {
	
	
	/**
     * this protected nested class implements autoscrolling
     */

    protected static class MyOtherDropTargetAutoScroller extends DropTargetAutoScroller {

        /**
         * construct a DropTargetAutoScroller
         * <P>
         * @param c the <code>Component</code>
         * @param p the <code>Point</code>
         */

        protected MyOtherDropTargetAutoScroller(Component c, Point p) {
            super(c,p);

            component  = c;
            autoScroll = (Autoscroll)component;

            Toolkit t  = Toolkit.getDefaultToolkit();

            Integer    initial  = Integer.valueOf(100);
            Integer    interval = Integer.valueOf(100);

            try {
                initial = (Integer)t.getDesktopProperty("DnD.Autoscroll.initialDelay");
            } catch (Exception e) {
                // ignore
            }

            try {
                interval = (Integer)t.getDesktopProperty("DnD.Autoscroll.interval");
            } catch (Exception e) {
                // ignore
            }

            timer  = new Timer(interval.intValue(), this);

            timer.setCoalesce(true);
            timer.setInitialDelay(initial.intValue());

            locn = p;
            prev = p;

            try {
                hysteresis = ((Integer)t.getDesktopProperty("DnD.Autoscroll.cursorHysteresis")).intValue();
            } catch (Exception e) {
                // ignore
            }

            timer.start();
        }

        /**
         * update the geometry of the autoscroll region
         */

        private void updateRegion() {
           Insets    i    = autoScroll.getAutoscrollInsets();
           Dimension size = component.getSize();

           if (size.width != outer.width || size.height != outer.height)
                outer.reshape(0, 0, size.width, size.height);

           if (inner.x != i.left || inner.y != i.top)
                inner.setLocation(i.left, i.top);

           int newWidth  = size.width -  (i.left + i.right);
           int newHeight = size.height - (i.top  + i.bottom);

           if (newWidth != inner.width || newHeight != inner.height)
                inner.setSize(newWidth, newHeight);

        }

        /**
         * cause autoscroll to occur
         * <P>
         * @param newLocn the <code>Point</code>
         */

        protected synchronized void updateLocation(Point newLocn) {
            prev = locn;
            locn = newLocn;

            if (Math.abs(locn.x - prev.x) > hysteresis ||
                Math.abs(locn.y - prev.y) > hysteresis) {
                if (timer.isRunning()) timer.stop();
            } else {
                if (!timer.isRunning()) timer.start();
            }
        }

        /**
         * cause autoscrolling to stop
         */

        protected void stop() { timer.stop(); }

        /**
         * cause autoscroll to occur
         * <P>
         * @param e the <code>ActionEvent</code>
         */

        public synchronized void actionPerformed(ActionEvent e) {
            updateRegion();

            if (outer.contains(locn) && !inner.contains(locn))
                autoScroll.autoscroll(locn);
        }

        /*
         * fields
         */

        private Component  component;
        private Autoscroll autoScroll;

        private Timer      timer;

        private Point      locn;
        private Point      prev;

        private Rectangle  outer = new Rectangle();
        private Rectangle  inner = new Rectangle();

        private int        hysteresis = 10;
    }

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

    /**
     * create an embedded autoscroller
     * <P>
     * @param c the <code>Component</code>
     * @param p the <code>Point</code>
     */

    @Override
    protected DropTargetAutoScroller createDropTargetAutoScroller(Component c,
    		Point p) {
    	// TODO Auto-generated method stub
    	return new MyOtherDropTargetAutoScroller(c, p);
    }

}