001/* ViewportLayout.java --
002   Copyright (C) 2002, 2004, 2006 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package javax.swing;
039
040import java.awt.Component;
041import java.awt.Container;
042import java.awt.Dimension;
043import java.awt.LayoutManager;
044import java.awt.Point;
045import java.awt.Rectangle;
046import java.io.Serializable;
047
048/**
049 * The default layout for {@link JViewport}. The viewport makes its view the
050 * same size as itself, but not smaller than its minimum size.
051 *
052 * If the port extends extends into space <em>past</em> the edge of the view,
053 * this layout manager moves the port up or to the left, in view space, by the
054 * amount of empty space (keep the lower and right edges lined up).
055 *
056 * @author  Andrew Selkirk
057 * @author  Graydon Hoare
058 * @author  Audrius Meskauskas (audriusa@Bioinformatics.org)
059 */
060public class ViewportLayout implements LayoutManager, Serializable
061{
062  private static final long serialVersionUID = -788225906076097229L;
063
064  public ViewportLayout()
065  {
066    // Nothing to do here.
067  }
068
069  /**
070   * The method is not used with this manager.
071   */
072  public void addLayoutComponent(String name, Component c)
073  {
074    // Nothing to do here.
075  }
076
077  /**
078   * The method is not used with this manager.
079   */
080  public void removeLayoutComponent(Component c)
081  {
082    // Nothing to do here.
083  }
084
085  /**
086   * Get the preferred layout size. If the view implements
087   * {@link Scrollable}, this method returns
088   * {@link Scrollable#getPreferredScrollableViewportSize}.
089   * Otherwise, it returns {@link Component#getPreferredSize()}.
090   *
091   * @return the preferred layout size, as described about.
092   */
093  public Dimension preferredLayoutSize(Container parent)
094  {
095    JViewport vp = (JViewport)parent;
096    Component view = vp.getView();
097    if (view != null)
098      {
099        if (view instanceof Scrollable)
100          return ((Scrollable)view).getPreferredScrollableViewportSize();
101        return view.getPreferredSize();
102      }
103    else
104      return new Dimension();
105  }
106
107  /**
108   * Get the minimum layout size. Normally this method returns the value,
109   * returned by the view method {@link Component#getMinimumSize()}.
110   *
111   * If the view is not set, the zero size is returned.
112   *
113   * @param parent the viewport
114   * @return the minimum layout size.
115   */
116  public Dimension minimumLayoutSize(Container parent)
117  {
118    // These values have been determined by the Mauve test for this method.
119    return new Dimension(4, 4);
120  }
121
122  /**
123   * Layout the view and viewport to respect the following rules. These are not
124   * precisely the rules described in sun's javadocs, but they are the rules
125   * which sun's swing implementation follows, if you watch its behavior:
126   * <ol>
127   * <li>If the port is smaller than the view, leave the view at its current
128   * size.</li>
129   * <li>If the view is smaller than the port, the view is top aligned.</li>
130   * <li>If the view tracks the port size, the view position is always zero and
131   * the size equal to the viewport size</li>
132   * <li>In {@link JViewport#setViewSize(Dimension)}, the view size is never
133   * set smaller that its minimum size.</li>
134   * </ol>
135   *
136   * @see JViewport#getViewSize
137   * @see JViewport#setViewSize
138   * @see JViewport#getViewPosition
139   * @see JViewport#setViewPosition
140   */
141  public void layoutContainer(Container parent)
142  {
143    // The way to interpret this function is basically to ignore the names
144    // of methods it calls, and focus on the variable names here. getViewRect
145    // doesn't, for example, return the view; it returns the port bounds in
146    // view space. Likwise setViewPosition doesn't reposition the view; it
147    // positions the port, in view coordinates.
148
149    JViewport port = (JViewport) parent;
150    Component view = port.getView();
151
152    if (view == null)
153      return;
154
155    // These dimensions and positions are in *view space*. Do not mix
156    // variables in here from port space (eg. parent.getBounds()). This
157    // function should be entirely in view space, because the methods on
158    // the viewport require inputs in view space.
159
160    Rectangle portBounds = port.getViewRect();
161    Dimension viewPref = new Dimension(view.getPreferredSize());
162
163    Point portLowerRight = new Point(portBounds.x + portBounds.width,
164                                     portBounds.y + portBounds.height);
165
166    // vertical implementation of the above rules
167    if (view instanceof Scrollable)
168      {
169        Scrollable sView = (Scrollable) view;
170
171        // If the view size matches viewport size, the port offset can
172        // only be zero.
173        if (sView.getScrollableTracksViewportWidth())
174          {
175            viewPref.width = portBounds.width;
176            portBounds.x = 0;
177          }
178        if (sView.getScrollableTracksViewportHeight())
179          {
180            viewPref.height = portBounds.height;
181            portBounds.y = 0;
182          }
183      }
184
185     if (viewPref.width < portBounds.width)
186       viewPref.width = portBounds.width;
187     if (viewPref.height < portBounds.height)
188       viewPref.height = portBounds.height;
189
190    // If the view is larger than the port, the port is top and right
191    // aligned.
192    if (portLowerRight.x > viewPref.width)
193      portBounds.x = 0;
194
195    if (portLowerRight.y > viewPref.height)
196      portBounds.y = 0;
197
198    port.setViewSize(viewPref);
199    port.setViewPosition(portBounds.getLocation());
200  }
201
202}