Change AutoScroll Bounds in JTextPane

Question

I cannot figure this out for the life of me. I would like to CHANGE the bounds for the autoscroll on a JTextPane that resides inside a JScrollPane when the user selects text and moves the mouse outside of the "autoscroll bounds".
The normal bounds for scrolling down a JTextPane (when inside a JScrollPane) are usually the bounds of the JTextPane itself. (You can verify this with my example by selecting some text with the mouse button held down, and moving your cursor outside the bottom of the window). I would like to move the bottom bounds up higher into the window (indicated by the black line that resides on the glasspane).
I have provided this example to use as a starting point. It doesn't do anything of use right now. I have tried about 20 things, but things have gotten so messed up, and the level of internal code that I started to mess around with got way over my head... so I'm just going to post this with a clean start, and hopefully we can move in a positive direction. I will relay my findings about a paticular route if we start moving down one i've already failed at.
Thanks for you time.
-Js
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.text.BadLocationException;
import javax.swing.text.StyledDocument;
public class AutoScrollTest extends JFrame
     //DATA
     private static final int Y_SCROLL_THRESHOLD = 150;
     //GUI
     private JPanel glassPanel;
     private JScrollPane scrollPane;
          private JTextPane textPane;
     public AutoScrollTest()
          this.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE);
          this.setGlassPane(getGlassPanel());
          this.setContentPane(getScrollPane());
          getGlassPanel().setVisible(true);
          this.pack();
          this.setVisible(true);
     private JPanel getGlassPanel()
          if(glassPanel == null)
               glassPanel = new JPanel()
                    public void paintComponent(Graphics g)
                         super.paintComponent(g);
                         g.setColor(Color.BLACK);
                         g.drawLine(0, Y_SCROLL_THRESHOLD, 300, Y_SCROLL_THRESHOLD);
               glassPanel.setOpaque(false);
          return glassPanel;
     private JScrollPane getScrollPane()
          if(scrollPane == null)
               scrollPane = new JScrollPane(getTextPane());
               scrollPane.setPreferredSize(new Dimension(300,300));
          return scrollPane;
     private JTextPane getTextPane()
          if(textPane == null)
               textPane = new JTextPane();
               try
                    StyledDocument sd = textPane.getStyledDocument();
                    for(int i=1; i<1000; i++)
                         sd.insertString(sd.getLength(),"This is line: " + i + "\n", null);
               catch(BadLocationException ble)
                    ble.printStackTrace();
          return textPane;
     public static void main(String args[])
          new AutoScrollTest();
}

Answer 1

camickr & StanislavL:
Great work guys. I have used both of your ideas... and it works GREAT! I'll split the dukes between you.
Please take a look at the finished code, its very cool. Again, thanks.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;
public class AutoScrollTest extends JFrame
     //DATA
     private static final int Y_SCROLL_THRESHOLD = 150;
     private Timer scrollTimer;
     //GUI
     private JPanel glassPanel;
     private JScrollPane scrollPane;
          private JTextPane textPane;
     public AutoScrollTest()
          this.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE);
          this.setGlassPane(getGlassPanel());
          this.setContentPane(getScrollPane());
          getGlassPanel().setVisible(true);
          this.pack();
          this.setVisible(true);
     private JPanel getGlassPanel()
          if(glassPanel == null)
               glassPanel = new JPanel()
                    public void paintComponent(Graphics g)
                         super.paintComponent(g);
                         g.setColor(Color.BLACK);
                         g.drawLine(0, Y_SCROLL_THRESHOLD, 300, Y_SCROLL_THRESHOLD);
               glassPanel.setOpaque(false);
          return glassPanel;
     private JScrollPane getScrollPane()
          if(scrollPane == null)
               scrollPane = new JScrollPane(getTextPane());
               scrollPane.setPreferredSize(new Dimension(300,300));
          return scrollPane;
     private JTextPane getTextPane()
          if(textPane == null)
               textPane = new JTextPane();
               MouseInputAdapter mia = new MouseInputAdapter()
                    public void mouseDragged(MouseEvent e)
                         Point viewPortPoint = getScrollPane().getViewport().getViewPosition();
                         if(e.getY()-viewPortPoint.getY() > Y_SCROLL_THRESHOLD)
                              getScrollTimer().start();
                         else
                              getScrollTimer().stop();
                    public void mouseReleased(MouseEvent e)
                         getScrollTimer().stop();
               textPane.addMouseListener(mia);
               textPane.addMouseMotionListener(mia);
               try
                    StyledDocument sd = textPane.getStyledDocument();
                    for(int i=1; i<1000; i++)
                         sd.insertString(sd.getLength(),"This is line: " + i + "\n", null);
               catch(BadLocationException ble)
                    ble.printStackTrace();
          return textPane;
     private Timer getScrollTimer()
          if(scrollTimer == null)
               scrollTimer = new Timer(60,new MyScrollListener(getTextPane(),getScrollPane().getVerticalScrollBar()));
          return scrollTimer;
     public static void main(String args[])
          new AutoScrollTest();
class MyScrollListener implements ActionListener
     private JTextPane textPane;
     private JScrollBar scrollBar;
     public MyScrollListener(JTextPane textPane, JScrollBar scrollBar)
          this.scrollBar = scrollBar;
          this.textPane = textPane;
     public void actionPerformed(ActionEvent e)
          //Move down the scrollbar
          scrollBar.setValue(scrollBar.getValue()+scrollBar.getBlockIncrement());
          //Update the mouse highlight
          PointerInfo mousePointerInfo = MouseInfo.getPointerInfo();
          Point convertedPoint = SwingUtilities.convertPoint(null,mousePointerInfo.getLocation(),textPane);
          Position.Bias[] bias = new Position.Bias[1];
          int mouseOffset = textPane.getUI().viewToModel(textPane,convertedPoint, bias);
          if (bias[0] == Position.Bias.Backward && mouseOffset != 0)
               --mouseOffset;
          textPane.setSelectionEnd(mouseOffset);
}