/* ScrollPane.java -- Scrolling window
   Copyright (C) 1999 Free Software Foundation, Inc.

This file is part of the non-peer AWT libraries of GNU Classpath.

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

This library 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 Library General Public License for more details.

You should have received a copy of the GNU Library General Public License
along with this library; if not, write to the Free Software Foundation
Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307 USA. */


package java.awt;

import java.awt.peer.ScrollPanePeer;
import java.awt.peer.ContainerPeer;
import java.awt.peer.ComponentPeer;

/**
  * This widget provides a scrollable region that allows a single 
  * subcomponent to be viewed through a smaller window.
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  */
public class ScrollPane extends Container implements java.io.Serializable
{

/*
 * 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);

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

/*
 * Constructors
 */

/**
  * Initializes a new instance of <code>ScrollPane</code> with a default
  * scrollbar policy of <code>SCROLLBARS_AS_NEEDED</code>.
  */
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.
  */
public
ScrollPane(int scrollbarDisplayPolicy)
{
  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(Scrollbar.HORIZONTAL);
      vAdjustable = new ScrollPaneAdjustable(Scrollbar.VERTICAL);
    }
}

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

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

  ScrollPaneAdjustable v = (ScrollPaneAdjustable)getVAdjustable();
  ScrollPaneAdjustable h = (ScrollPaneAdjustable)getHAdjustable();

  if ((v != null) && v.isVisible())
    viewsize.width = viewsize.width - v.getSize().width;
  if ((h != null) && h.isVisible())
    viewsize.height = viewsize.height - v.getSize().height;

  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?
}

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

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

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

/**
  * Returns the current scroll position of the viewport.
  *
  * @return The current scroll position of the viewport.
  */
public Point
getScrollPosition()
{
  int x = 0;
  int y = 0;

  Adjustable v = getVAdjustable();
  Adjustable h = getHAdjustable();

  if (v != null)
    y = v.getValue();
  if (h != null)
    x = h.getValue();

  return(new Point(x, y));
}

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

/**
  * Sets the scroll position to the specified value.
  *
  * @param scrollPosition The new scrollPosition.
  *
  * @exception IllegalArgumentException If the specified value is outside
  * the legal scrolling range.
  */
public void
setScrollPosition(Point scrollPosition) throws IllegalArgumentException
{
  setScrollPosition(scrollPosition.x, scrollPosition.y);
}

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

/**
  * Sets the scroll position to the specified value.
  *
  * @param x The new X coordinate of the scroll position.
  * @param y The new Y coordinate of the scroll position.
  *
  * @exception IllegalArgumentException If the specified value is outside
  * the legal scrolling range.
  */
public void
setScrollPosition(int x, int y)
{
  Adjustable h = getHAdjustable();
  Adjustable v = getVAdjustable();

  if (h != null)
    h.setValue(x);
  if (v != null)
    v.setValue(y);

  ScrollPanePeer spp = (ScrollPanePeer)getPeer();
  if (spp != null)
    spp.setScrollPosition(x, y);
}

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

/**
  * Notifies this object that it should create its native peer.
  */
public void
addNotify()
{
  if (getPeer() == null)
    return;

  setPeer((ComponentPeer)getToolkit().createScrollPane(this));

  if (hAdjustable != null)
    hAdjustable.addNotify();
  if (vAdjustable != null)
    vAdjustable.removeNotify();
}

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

/**
  * Notifies this object that it should destroy its native peers.
  */
public void
removeNotify()
{
  if (hAdjustable != null)
    hAdjustable.removeNotify();
  if (vAdjustable != null)
    vAdjustable.removeNotify();

  super.removeNotify();
}

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

/**
  * Adds the specified child component to this container.  A 
  * <code>ScrollPane</code> can have at most one child, so if a second
  * one is added, then first one is removed.
  *
  * @param component The component to add to this container.
  * @param constraints A list of layout constraints for this object.
  * @param index The index at which to add the child, which is ignored
  * in this implementation.
  */
public final void
addImpl(Component component, Object constraints, int index)
{
  Component[] list = getComponents();
  if ((list != null) && (list.length > 0))
    remove(list[0]);

  super.addImpl(component, constraints, -1);

  doLayout();
}

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

/**
  * Lays out this component.  This consists of resizing the sole child
  * component to its perferred size.
  */
public void
doLayout()
{
  Component[] list = getComponents();
  if ((list != null) && (list.length > 0))
    {
      Dimension dim = list[0].getPreferredSize();
      list[0].resize(dim);

      Point p = getScrollPosition();
      if (p.x > dim.width)
        p.x = dim.width;
      if (p.y > dim.height)
        p.y = dim.height;

      setScrollPosition(p);
    }
}

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

/**
  * Lays out this component.  This consists of resizing the sole child
  * component to its perferred size.
  *
  * @deprecated This method is deprecated in favor of
  * <code>doLayout()</code>.
  */
public void
layout()
{
  doLayout();
}

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

/**
  * This method overrides its superclass method to ensure no layout
  * manager is set for this container.  <code>ScrollPane</code>'s do
  * not have layout managers.
  *
  * @param layoutManager Ignored
  */
public final void
setLayout(LayoutManager layoutManager)
{
  return;
}

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

/**
  * Prints all of the components in this container.
  *
  * @param graphics The desired graphics context for printing.
  */
public void
printComponents(Graphics graphics)
{
  super.printComponents(graphics);
}

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

/**
  * Returns a debug string for this object.
  *
  * @return A debug string for this object.
  */
public String
paramString()
{
  return(getClass().getName());
}

} // class ScrollPane