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:   }
  60:   public void addLayoutComponent(String name, Component c) 
  61:   {
  62:   }
  63:   public void removeLayoutComponent(Component c) 
  64:   {
  65:   }
  66: 
  67:   public Dimension preferredLayoutSize(Container parent) 
  68:   {
  69:     JViewport vp = (JViewport)parent;
  70:     Component view = vp.getView();
  71:     if (view != null)
  72:       {
  73:         if (view instanceof Scrollable)
  74:           return ((Scrollable)view).getPreferredScrollableViewportSize();
  75:         return view.getPreferredSize();
  76:       }
  77:     else
  78:       return new Dimension();
  79:   }
  80: 
  81:   public Dimension minimumLayoutSize(Container parent) 
  82:   {
  83:     JViewport vp = (JViewport)parent;
  84:     Component view = vp.getView();
  85:     if (view != null)
  86:       return view.getMinimumSize();
  87:     else
  88:       return new Dimension();
  89:   }
  90: 
  91:   /**
  92:    * Layout the view and viewport to respect the following rules. These are
  93:    * not precisely the rules described in sun's javadocs, but they are the
  94:    * rules which sun's swing implementation follows, if you watch its
  95:    * behavior:
  96:    *
  97:    * <ol> 
  98:    * 
  99:    * <li>If the port is larger than the view's minimum size, put the port
 100:    * at view position <code>(0,0)</code> and make the view's size equal to
 101:    * the port's.</li>
 102:    *
 103:    * <li>If the port is smaller than the view, leave the view at its
 104:    * minimum size. also, do not move the port, <em>unless</em> the port
 105:    * extends into space <em>past</em> the edge of the view. If so, move the
 106:    * port up or to the left, in view space, by the amount of empty space
 107:    * (keep the lower and right edges lined up)</li>
 108:    *
 109:    * </ol>
 110:    *
 111:    * @see JViewport#getViewSize
 112:    * @see JViewport#setViewSize
 113:    * @see JViewport#getViewPosition
 114:    * @see JViewport#setViewPosition
 115:    */
 116: 
 117:   public void layoutContainer(Container parent) 
 118:   {
 119:     // The way to interpret this function is basically to ignore the names
 120:     // of methods it calls, and focus on the variable names here. getViewRect
 121:     // doesn't, for example, return the view; it returns the port bounds in
 122:     // view space. Likwise setViewPosition doesn't reposition the view; it 
 123:     // positions the port, in view coordinates.
 124: 
 125:     JViewport port = (JViewport) parent;    
 126:     Component view = port.getView();
 127:     
 128:     if (view == null)
 129:       return;
 130: 
 131:     // These dimensions and positions are in *view space*.  Do not mix
 132:     // variables in here from port space (eg. parent.getBounds()). This
 133:     // function should be entirely in view space, because the methods on
 134:     // the viewport require inputs in view space.
 135: 
 136:     Rectangle portBounds = port.getViewRect();
 137:     Dimension viewPref = view.getPreferredSize();
 138:     Dimension viewMinimum = view.getMinimumSize();
 139:     Point portLowerRight = new Point(portBounds.x + portBounds.width,
 140:                                      portBounds.y + portBounds.height);
 141:         
 142:     // vertical implementation of the above rules
 143:     if (portBounds.height >= viewMinimum.height)
 144:       {
 145:         portBounds.y = 0;
 146:         if ( !(view instanceof Scrollable) || ((Scrollable)view).getScrollableTracksViewportHeight())
 147:           viewPref.height = portBounds.height;
 148:       }
 149:     else
 150:       {
 151:         viewPref.height = viewMinimum.height;
 152:         int overextension = portLowerRight.y - viewPref.height;
 153:         if (overextension > 0)
 154:             portBounds.y -= overextension;
 155:       }
 156: 
 157:     // horizontal implementation of the above rules
 158:     if (portBounds.width >= viewMinimum.width)
 159:       {
 160:         portBounds.x = 0;
 161:         if ( !(view instanceof Scrollable) || ((Scrollable)view).getScrollableTracksViewportWidth())
 162:           viewPref.width = portBounds.width;
 163:       }
 164:     else
 165:       {
 166:         viewPref.width = viewMinimum.width;
 167:         int overextension = portLowerRight.x - viewPref.width;
 168:         if (overextension > 0)
 169:             portBounds.x -= overextension;
 170:       }
 171: 
 172:     port.setViewPosition(portBounds.getLocation());
 173:     port.setViewSize(viewPref);
 174:   }
 175: }