libjava/classpath/javax/swing/ViewportLayout.java

   1 /* ViewportLayout.java --
   2    Copyright (C) 2002, 2004 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package javax.swing;
  39
  40 import java.awt.Component;
  41 import java.awt.Container;
  42 import java.awt.Dimension;
  43 import java.awt.LayoutManager;
  44 import java.awt.Point;
  45 import java.awt.Rectangle;
  46 import java.io.Serializable;
  47
  48 /**
  49  * ViewportLayout
  50  * @author      Andrew Selkirk
  51  * @author      Graydon Hoare
  52  */
  53 public class ViewportLayout implements LayoutManager, Serializable
  54 {
  55   private static final long serialVersionUID = -788225906076097229L;
  56
  57   public ViewportLayout()
  58   {
  59     // Nothing to do here.
  60   }
  61
  62   public void addLayoutComponent(String name, Component c)
  63   {
  64     // Nothing to do here.
  65   }
  66
  67   public void removeLayoutComponent(Component c)
  68   {
  69     // Nothing to do here.
  70   }
  71
  72   public Dimension preferredLayoutSize(Container parent)
  73   {
  74     JViewport vp = (JViewport)parent;
  75     Component view = vp.getView();
  76     if (view != null)
  77       {
  78         if (view instanceof Scrollable)
  79           return ((Scrollable)view).getPreferredScrollableViewportSize();
  80         return view.getPreferredSize();
  81       }
  82     else
  83       return new Dimension();
  84   }
  85
  86   public Dimension minimumLayoutSize(Container parent)
  87   {
  88     JViewport vp = (JViewport)parent;
  89     Component view = vp.getView();
  90     if (view != null)
  91       return view.getMinimumSize();
  92     else
  93       return new Dimension();
  94   }
  95
  96   /**
  97    * Layout the view and viewport to respect the following rules. These are
  98    * not precisely the rules described in sun's javadocs, but they are the
  99    * rules which sun's swing implementation follows, if you watch its
 100    * behavior:
 101    *
 102    * <ol>
 103    *
 104    * <li>If the port is larger than the view's minimum size, put the port
 105    * at view position <code>(0,0)</code> and make the view's size equal to
 106    * the port's.</li>
 107    *
 108    * <li>If the port is smaller than the view, leave the view at its
 109    * minimum size. also, do not move the port, <em>unless</em> the port
 110    * extends into space <em>past</em> the edge of the view. If so, move the
 111    * port up or to the left, in view space, by the amount of empty space
 112    * (keep the lower and right edges lined up)</li>
 113    *
 114    * </ol>
 115    *
 116    * @see JViewport#getViewSize
 117    * @see JViewport#setViewSize
 118    * @see JViewport#getViewPosition
 119    * @see JViewport#setViewPosition
 120    */
 121
 122   public void layoutContainer(Container parent)
 123   {
 124     // The way to interpret this function is basically to ignore the names
 125     // of methods it calls, and focus on the variable names here. getViewRect
 126     // doesn't, for example, return the view; it returns the port bounds in
 127     // view space. Likwise setViewPosition doesn't reposition the view; it
 128     // positions the port, in view coordinates.
 129
 130     JViewport port = (JViewport) parent;
 131     Component view = port.getView();
 132
 133     if (view == null)
 134       return;
 135
 136     // These dimensions and positions are in *view space*.  Do not mix
 137     // variables in here from port space (eg. parent.getBounds()). This
 138     // function should be entirely in view space, because the methods on
 139     // the viewport require inputs in view space.
 140
 141     Rectangle portBounds = port.getViewRect();
 142     Dimension viewPref = view.getPreferredSize();
 143     Dimension viewMinimum = view.getMinimumSize();
 144     Point portLowerRight = new Point(portBounds.x + portBounds.width,
 145                                      portBounds.y + portBounds.height);
 146
 147     // vertical implementation of the above rules
 148     if ((! (view instanceof Scrollable) && viewPref.height < portBounds.height
 149          || (view instanceof Scrollable
 150             && ((Scrollable) view).getScrollableTracksViewportHeight())))
 151       viewPref.height = portBounds.height;
 152
 153     if (portBounds.height >= viewMinimum.height)
 154       portBounds.y = 0;
 155     else
 156       {
 157         int overextension = portLowerRight.y - viewPref.height;
 158         if (overextension > 0)
 159             portBounds.y -= overextension;
 160       }
 161
 162     // horizontal implementation of the above rules
 163     if ((! (view instanceof Scrollable) && viewPref.width < portBounds.width
 164          || (view instanceof Scrollable
 165          && ((Scrollable) view).getScrollableTracksViewportWidth())))
 166       viewPref.width = portBounds.width;
 167
 168     if (portBounds.width >= viewMinimum.width)
 169       portBounds.x = 0;
 170     else
 171       {
 172         int overextension = portLowerRight.x - viewPref.width;
 173         if (overextension > 0)
 174             portBounds.x -= overextension;
 175       }
 176
 177     port.setViewPosition(portBounds.getLocation());
 178     port.setViewSize(viewPref);
 179   }
 180 }