basicscrollpaneui.java

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/* BasicScrollPaneUI.java
   Copyright (C) 2002, 2004, 2005 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath 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 for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package javax.swing.plaf.basic;

import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.ContainerEvent;
import java.awt.event.ContainerListener;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

import javax.swing.JComponent;
import javax.swing.JScrollBar;
import javax.swing.JScrollPane;
import javax.swing.JViewport;
import javax.swing.LookAndFeel;
import javax.swing.ScrollPaneConstants;
import javax.swing.ScrollPaneLayout;
import javax.swing.Scrollable;
import javax.swing.SwingConstants;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.plaf.ComponentUI;
import javax.swing.plaf.ScrollPaneUI;

public class BasicScrollPaneUI extends ScrollPaneUI
  implements ScrollPaneConstants
{

  /**
   * Listens for changes in the state of the horizontal scrollbar's model and
   * updates the scrollpane accordingly.
   *
   * @author Roman Kennke ([e-mail])
   */
  public class HSBChangeListener implements ChangeListener
  {

    /**
     * Receives notification when the state of the horizontal scrollbar
     * model has changed.
     *
     * @param event the change event
     */
    public void stateChanged(ChangeEvent event)
    {
      JScrollBar hsb = scrollpane.getHorizontalScrollBar();
      JViewport vp = scrollpane.getViewport();
      Point viewPosition = vp.getViewPosition();
      int xpos = hsb.getValue();

      if (xpos != viewPosition.x)
        {
          viewPosition.x = xpos;
          vp.setViewPosition(viewPosition);
        }

      viewPosition.y = 0;
      JViewport columnHeader = scrollpane.getColumnHeader();
      if (columnHeader != null 
          && !columnHeader.getViewPosition().equals(viewPosition))
        columnHeader.setViewPosition(viewPosition);
    }

  }

  /**
   * Listens for changes in the state of the vertical scrollbar's model and
   * updates the scrollpane accordingly.
   *
   * @author Roman Kennke ([e-mail])
   */
  public class VSBChangeListener implements ChangeListener
  {

    /**
     * Receives notification when the state of the vertical scrollbar
     * model has changed.
     *
     * @param event the change event
     */
    public void stateChanged(ChangeEvent event)
    {
      JScrollBar vsb = scrollpane.getVerticalScrollBar();
      JViewport vp = scrollpane.getViewport();
      Point viewPosition = vp.getViewPosition();
      int ypos = vsb.getValue();
      if (ypos != viewPosition.y)
        {
          viewPosition.y = ypos;
          vp.setViewPosition(viewPosition);
        }

      viewPosition.x = 0;
      JViewport rowHeader = scrollpane.getRowHeader();
      if (rowHeader != null 
          && !rowHeader.getViewPosition().equals(viewPosition))
        rowHeader.setViewPosition(viewPosition);
    }
 
  }

  /**
   * Listens for changes of the viewport's extent size and updates the
   * scrollpane accordingly.
   *
   * @author Roman Kennke ([e-mail])
   */
  public class ViewportChangeHandler implements ChangeListener
  {

    /**
     * Receives notification when the view's size, position or extent size
     * changes. When the extents size has changed, this method calls
     * {@link BasicScrollPaneUI#syncScrollPaneWithViewport()} to adjust the
     * scrollbars extents as well.
     * 
     * @param event the change event
     */
    public void stateChanged(ChangeEvent event)
    {
      JViewport vp = scrollpane.getViewport();
      JScrollBar hsb = scrollpane.getHorizontalScrollBar();
      JScrollBar vsb = scrollpane.getVerticalScrollBar();
      syncScrollPaneWithViewport();
    }

  }

  /**
   * Listens for property changes on the scrollpane and update the view
   * accordingly.
   *
   * @author Roman Kennke ([e-mail])
   */
  public class PropertyChangeHandler implements PropertyChangeListener
  {

    /**
     * Receives notification when any of the scrollpane's bound property
     * changes. This method calls the appropriate update method on the
     * <code>ScrollBarUI</code>.
     *
     * @param e the property change event
     *
     * @see BasicScrollPaneUI#updateColumnHeader(PropertyChangeEvent)
     * @see BasicScrollPaneUI#updateRowHeader(PropertyChangeEvent)
     * @see BasicScrollPaneUI#updateScrollBarDisplayPolicy(PropertyChangeEvent)
     * @see BasicScrollPaneUI#updateViewport(PropertyChangeEvent)
     */
    public void propertyChange(PropertyChangeEvent e)
    {
      String propName = e.getPropertyName();
      if (propName.equals("viewport"))
        updateViewport(e);
      else if (propName.equals("rowHeader"))
        updateRowHeader(e);
      else if (propName.equals("columnHeader"))
        updateColumnHeader(e);
      else if (propName.equals("horizontalScrollBarPolicy")
          || e.getPropertyName().equals("verticalScrollBarPolicy"))
        updateScrollBarDisplayPolicy(e);
      else if (propName.equals("verticalScrollBar"))
        {
          JScrollBar oldSb = (JScrollBar) e.getOldValue();
          oldSb.getModel().removeChangeListener(vsbChangeListener);
          JScrollBar newSb = (JScrollBar) e.getNewValue();
          newSb.getModel().addChangeListener(vsbChangeListener);
        }
      else if (propName.equals("horizontalScrollBar"))
        {
          JScrollBar oldSb = (JScrollBar) e.getOldValue();
          oldSb.getModel().removeChangeListener(hsbChangeListener);
          JScrollBar newSb = (JScrollBar) e.getNewValue();
          newSb.getModel().addChangeListener(hsbChangeListener);
        }
    }

  }

  /**
   * Listens for mouse wheel events and update the scrollpane accordingly.
   *
   * @author Roman Kennke ([e-mail])
   *
   * @since 1.4
   */
  protected class MouseWheelHandler implements MouseWheelListener
  {
    /**
     * Use to compute the visible rectangle.
     */
    final Rectangle rect = new Rectangle();

    /**
     * Scroll with the mouse whell.
     * 
     * @author Audrius Meskauskas ([e-mail])
     */
    public void mouseWheelMoved(MouseWheelEvent e)
    {
      if (scrollpane.getViewport().getComponentCount() == 0)
        return;

      Component target = scrollpane.getViewport().getComponent(0);
      JScrollBar bar = scrollpane.getVerticalScrollBar();
      Scrollable scrollable = (target instanceof Scrollable) ? (Scrollable) target
                                                            : null;

      boolean tracksHeight = scrollable != null
                             && scrollable.getScrollableTracksViewportHeight();
      int wheel = e.getWheelRotation() * ROWS_PER_WHEEL_CLICK;
      int delta;

      // If possible, scroll vertically.
      if (bar != null && ! tracksHeight)
        {
          if (scrollable != null)
            {
              bounds(target);
              delta = scrollable.getScrollableUnitIncrement(
                rect, SwingConstants.VERTICAL, wheel);
            }
          else
            {
              // Scroll non scrollables.
              delta = wheel * SCROLL_NON_SCROLLABLES;
            }
          scroll(bar, delta);
        }
      // If not, try to scroll horizontally
      else
        {
          bar = scrollpane.getHorizontalScrollBar();
          boolean tracksWidth = scrollable != null
                                && scrollable.getScrollableTracksViewportWidth();

          if (bar != null && ! tracksWidth)
            {
              if (scrollable != null)
                {
                  bounds(target);
                  delta = scrollable.getScrollableUnitIncrement(
                     rect, SwingConstants.HORIZONTAL, wheel);
                }
              else
                {
                  // Scroll non scrollables.
                  delta = wheel * SCROLL_NON_SCROLLABLES;
                }
              scroll(bar, delta);
            }
        }
    }
    
    /**
     * Place the component bounds into rect. The x and y values 
     * need to be reversed.
     * 
     * @param target the target being scrolled
     */
    final void bounds(Component target)
    {
      // Viewport bounds, translated by the scroll bar positions.
      target.getParent().getBounds(rect);
      rect.x = getValue(scrollpane.getHorizontalScrollBar());
      rect.y = getValue(scrollpane.getVerticalScrollBar());
    }
    
    /**
     * Get the scroll bar value or null if there is no such scroll bar.
     */
    final int getValue(JScrollBar bar)
    {
      return bar != null ? bar.getValue() : 0;
    }
    
    /**
     * Scroll the given distance.
     * 
     * @param bar the scrollbar to scroll
     * @param delta the distance
     */
    final void scroll(JScrollBar bar, int delta)
    {
      int y = bar.getValue() + delta;

      if (y < bar.getMinimum())
        y = bar.getMinimum();
      if (y > bar.getMaximum())
        y = bar.getMaximum();

      bar.setValue(y);
    }
  }
  
  /**
   * Adds/removes the mouse wheel listener when the component is added/removed
   * to/from the scroll pane view port.
   * 
   * @author Audrius Meskauskas ([e-mail])