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/* ViewportLayout.java --

   Copyright (C) 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 javax.swing;

import java.awt.Component;

import java.awt.Container;

import java.awt.Dimension;

import java.awt.LayoutManager;

import java.awt.Point;

import java.awt.Rectangle;

import java.io.Serializable;

/**

 * ViewportLayout

 * @author      Andrew Selkirk

 * @author      Graydon Hoare

 */

public class ViewportLayout implements LayoutManager, Serializable

{

  private static final long serialVersionUID = -788225906076097229L;

  public ViewportLayout()

  {

    // Nothing to do here.

  }

  public void addLayoutComponent(String name, Component c)

  {

    // Nothing to do here.

  }

  public void removeLayoutComponent(Component c)

  {

    // Nothing to do here.

  }

  public Dimension preferredLayoutSize(Container parent)

  {

    JViewport vp = (JViewport)parent;

    Component view = vp.getView();

    if (view != null)

      {

        if (view instanceof Scrollable)

          return ((Scrollable)view).getPreferredScrollableViewportSize();

        return view.getPreferredSize();

      }

    else

      return new Dimension();

  }

  public Dimension minimumLayoutSize(Container parent)

  {

    JViewport vp = (JViewport)parent;

    Component view = vp.getView();

    if (view != null)

      return view.getMinimumSize();

    else

      return new Dimension();

  }

  /**

   * Layout the view and viewport to respect the following rules. These are

   * not precisely the rules described in sun's javadocs, but they are the

   * rules which sun's swing implementation follows, if you watch its

   * behavior:

   *

   * <ol>

   *

   * <li>If the port is larger than the view's minimum size, put the port

   * at view position <code>(0,0)</code> and make the view's size equal to

   * the port's.</li>

   *

   * <li>If the port is smaller than the view, leave the view at its

   * minimum size. also, do not move the port, <em>unless</em> the port

   * extends into space <em>past</em> the edge of the view. If so, move the

   * port up or to the left, in view space, by the amount of empty space

   * (keep the lower and right edges lined up)</li>

   *

   * </ol>

   *

   * @see JViewport#getViewSize

   * @see JViewport#setViewSize

   * @see JViewport#getViewPosition

   * @see JViewport#setViewPosition

   */

  public void layoutContainer(Container parent)

  {

    // The way to interpret this function is basically to ignore the names

    // of methods it calls, and focus on the variable names here. getViewRect

    // doesn't, for example, return the view; it returns the port bounds in

    // view space. Likwise setViewPosition doesn't reposition the view; it 

    // positions the port, in view coordinates.

    JViewport port = (JViewport) parent;

    Component view = port.getView();

    if (view == null)

      return;

    // These dimensions and positions are in *view space*.  Do not mix

    // variables in here from port space (eg. parent.getBounds()). This

    // function should be entirely in view space, because the methods on

    // the viewport require inputs in view space.

    Rectangle portBounds = port.getViewRect();

    Dimension viewPref = view.getPreferredSize();

    Dimension viewMinimum = view.getMinimumSize();

    Point portLowerRight = new Point(portBounds.x + portBounds.width,

                                     portBounds.y + portBounds.height);

    // vertical implementation of the above rules

    if (portBounds.height >= viewMinimum.height)

      {

        portBounds.y = 0;

        if ( !(view instanceof Scrollable) || ((Scrollable)view).getScrollableTracksViewportHeight())

          viewPref.height = portBounds.height;

      }

    else

      {

        viewPref.height = viewMinimum.height;

        int overextension = portLowerRight.y - viewPref.height;

        if (overextension > 0)

            portBounds.y -= overextension;

      }

    // horizontal implementation of the above rules

    if (portBounds.width >= viewMinimum.width)

      {

        portBounds.x = 0;

        if ( !(view instanceof Scrollable) || ((Scrollable)view).getScrollableTracksViewportWidth())

          viewPref.width = portBounds.width;

      }

    else

      {

        viewPref.width = viewMinimum.width;

        int overextension = portLowerRight.x - viewPref.width;

        if (overextension > 0)

            portBounds.x -= overextension;

      }

    port.setViewPosition(portBounds.getLocation());

    port.setViewSize(viewPref);

  }

}