scrollpane.java

gcc的组建

/* ScrollPane.java -- Scrolling window
   Copyright (C) 1999, 2002, 2004  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 java.awt;

import java.awt.event.MouseEvent;
import java.awt.peer.ComponentPeer;
import java.awt.peer.ScrollPanePeer;

import javax.accessibility.Accessible;
import javax.accessibility.AccessibleContext;
import javax.accessibility.AccessibleRole;

/**
  * This widget provides a scrollable region that allows a single 
  * subcomponent to be viewed through a smaller window.
  *
  * @author Aaron M. Renn ([e-mail])
  */
public class ScrollPane extends Container implements Accessible
{

/*
 * Static Variables
 */

/**
  * Constant indicating that scrollbars are created as needed in this
  * windows.
  */
public static final int SCROLLBARS_AS_NEEDED = 0;

/**
  * Constant indicating that scrollbars are always displayed in this
  * window.
  */
public static final int SCROLLBARS_ALWAYS = 1;

/**
  * Constant indicating that scrollbars are never displayed in this window.
  */
public static final int SCROLLBARS_NEVER = 2;

// Serialization constant
private static final long serialVersionUID = 7956609840827222915L;

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

/*
 * Instance Variables
 */

/**
  * @serial The horizontal scrollbar for this window.  The methods
  * <code>setMinimum()</code>, <code>setMaximum</code>, and
  * <code>setVisibleAmount</code> must not be called on this scrollbar.
  */
private ScrollPaneAdjustable hAdjustable;

/**
  * @serial The vertical scrollbar for this window.  The methods
  * <code>setMinimum()</code>, <code>setMaximum</code>, and
  * <code>setVisibleAmount</code> must not be called on this scrollbar.
  */
private ScrollPaneAdjustable vAdjustable;

/**
  * @serial Indicates when scrollbars are displayed in this window, will
  * be one of the constants from this class.
  */
private int scrollbarDisplayPolicy;

// Current scroll position
private Point scrollPosition = new Point(0, 0);

private boolean wheelScrollingEnabled;

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

/*
 * Constructors
 */

/**
  * Initializes a new instance of <code>ScrollPane</code> with a default
  * scrollbar policy of <code>SCROLLBARS_AS_NEEDED</code>.
  *
  * @exception HeadlessException If GraphicsEnvironment.isHeadless() is true.
  */
public
ScrollPane()
{
  this(SCROLLBARS_AS_NEEDED);
}

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

/**
  * Initializes a new instance of <code>ScrollPane</code> with the
  * specified scrollbar policy.
  *
  * @param scrollbarDisplayPolicy When to display scrollbars, which must
  * be one of the constants defined in this class.
  *
  * @exception HeadlessException If GraphicsEnvironment.isHeadless() is true.
  */
public
ScrollPane(int scrollbarDisplayPolicy)
{
  if (GraphicsEnvironment.isHeadless ())
    throw new HeadlessException ();

  this.scrollbarDisplayPolicy = scrollbarDisplayPolicy;

  if (scrollbarDisplayPolicy != SCROLLBARS_ALWAYS
      && scrollbarDisplayPolicy != SCROLLBARS_AS_NEEDED
      && scrollbarDisplayPolicy != SCROLLBARS_NEVER)
    throw new IllegalArgumentException("Bad scrollbarDisplayPolicy: " +
                                       scrollbarDisplayPolicy);

  if (scrollbarDisplayPolicy != SCROLLBARS_NEVER)
    {
      hAdjustable = new ScrollPaneAdjustable (this, Scrollbar.HORIZONTAL);
      vAdjustable = new ScrollPaneAdjustable (this, Scrollbar.VERTICAL);
    }

  wheelScrollingEnabled = true;

  // Default size.
  setSize(100,100);
}

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

/*
 * Instance Variables
 */

/**
  * Returns the current scrollbar display policy.
  *
  * @return The current scrollbar display policy.
  */
public int
getScrollbarDisplayPolicy()
{
  return(scrollbarDisplayPolicy);
}

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

/**
  * Returns the horizontal scrollbar for this object.  If the scrollbar
  * display policy is set to <code>SCROLLBARS_NEVER</code> then this
  * will be <code>null</code>.
  *
  * @return The horizontal scrollbar for this window.
  */
public Adjustable
getHAdjustable()
{
  return(hAdjustable);
}

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

/**
  * Returns the vertical scrollbar for this object.  If the scrollbar
  * display policy is set to <code>SCROLLBARS_NEVER</code> then this
  * will be <code>null</code>.
  *
  * @return The horizontal scrollbar for this window.
  */
public Adjustable
getVAdjustable()
{
  return(vAdjustable);
}

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

/**
  * Returns the current viewport size.  The viewport is the region of
  * this object's window where the child is actually displayed.
  *
  * @return The viewport size.
  */
public Dimension getViewportSize ()
{
  Dimension viewsize = getSize ();
  Insets insets = getInsets ();

  viewsize.width -= (insets.left + insets.right);
  viewsize.height -= (insets.top + insets.bottom);

  Component[] list = getComponents();
  if ((list == null) || (list.length <= 0))
    return viewsize;

  Dimension dim = list[0].getPreferredSize();

  if (dim.width <= 0 && dim.height <= 0)
    return viewsize;

  int vScrollbarWidth = getVScrollbarWidth ();
  int hScrollbarHeight = getHScrollbarHeight ();

  if (scrollbarDisplayPolicy == SCROLLBARS_ALWAYS)
    {
      viewsize.width -= vScrollbarWidth;
      viewsize.height -= hScrollbarHeight;
      return viewsize;
    }

  if (scrollbarDisplayPolicy == SCROLLBARS_NEVER)
    return viewsize;

  // The scroll policy is SCROLLBARS_AS_NEEDED, so we need to see if
  // either scrollbar is needed.

  // Assume we don't need either scrollbar.
  boolean mayNeedVertical = false;
  boolean mayNeedHorizontal = false;

  boolean needVertical = false;
  boolean needHorizontal = false;

  // Check if we need vertical scrollbars.  If we do, then we need to
  // subtract the width of the vertical scrollbar from the viewport's
  // width.
  if (dim.height > viewsize.height)
    needVertical = true;
  else if (dim.height > (viewsize.height - hScrollbarHeight))
    // This is tricky.  In this case the child is tall enough that its
    // bottom edge would be covered by a horizontal scrollbar, if one
    // were present.  This means that if there's a horizontal
    // scrollbar then we need a vertical scrollbar.
    mayNeedVertical = true;

  if (dim.width > viewsize.width)
    needHorizontal = true;
  else if (dim.width > (viewsize.width - vScrollbarWidth))
    mayNeedHorizontal = true;

  if (needVertical && mayNeedHorizontal)
    needHorizontal = true;

  if (needHorizontal && mayNeedVertical)
    needVertical = true;

  if (needHorizontal)
    viewsize.height -= hScrollbarHeight;

  if (needVertical)
    viewsize.width -= vScrollbarWidth;

  return viewsize;
}

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

/**
  * Returns the height of a horizontal scrollbar.
  *
  * @return The height of a horizontal scrollbar.
  */
public int
getHScrollbarHeight()
{
  ScrollPanePeer spp = (ScrollPanePeer)getPeer();
  if (spp != null)
    return(spp.getHScrollbarHeight());
  else
    return(0); // FIXME: What to do here?