Source for javax.swing.ViewportLayout

   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: }