libjava/gnu/awt/LightweightRedirector.java

   1 /* Copyright (C) 2000  Free Software Foundation
   2
   3    This file is part of libgcj.
   4
   5 This software is copyrighted work licensed under the terms of the
   6 Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
   7 details.  */
   8
   9 package gnu.awt;
  10
  11 import java.awt.AWTEvent;
  12 import java.awt.AWTError;
  13 import java.awt.Component;
  14 import java.awt.Container;
  15 import java.awt.event.MouseEvent;
  16 import java.awt.event.InputEvent;
  17
  18 /**
  19  * Encapsulates the logic required to dispatch events to the correct
  20  * component in a component tree that may contain lightweight
  21  * components. Toolkits typically only identify heavyweight components
  22  * as the source of events. This class redirects the events to the
  23  * appropriate lightweight children of the heavyweight component.
  24  */
  25 public class LightweightRedirector
  26 {
  27   final static int LAST_BUTTON_NUMBER = 3;
  28
  29   /* We sacrifice one array element to allow the button number to
  30      match the index of this array. */
  31   Component[] releaseTargets = new Component[LAST_BUTTON_NUMBER+1];
  32
  33   /**
  34    *
  35    * Modifies or replaces the given event with an event that has been
  36    * properly redirected.  State of button presses are kept so that
  37    * button releases can be redirected to the same component as the
  38    * button press.  It is required that all events are sent through
  39    * this method in chronological order.
  40    */
  41   public AWTEvent redirect(AWTEvent event)
  42   {
  43     if (event instanceof MouseEvent)
  44       return redirectMouse((MouseEvent) event);
  45
  46     /* In case we don't know how to redirect the event, simply return
  47        the event unchanged. */
  48     return event;
  49   }
  50
  51   MouseEvent redirectMouse(MouseEvent event)
  52   {
  53     int button = getButtonNumber(event);
  54     int id = event.getID();
  55
  56     Component heavySource = (Component) event.getSource();
  57     Component source = heavySource;
  58     int x = event.getX();
  59     int y = event.getY();
  60
  61     if (id == MouseEvent.MOUSE_RELEASED)
  62       {
  63         Component target = releaseTargets[button];
  64
  65         if (target != null)
  66           {
  67             releaseTargets[button] = null;
  68             source = target;
  69
  70             Component child = source;
  71             while (child != heavySource)
  72               {
  73                 x -= child.getX();
  74                 y -= child.getY();
  75                 child = child.getParent();
  76                 if (child == null)
  77                   System.err.println("warning, orphaned release target");
  78               }
  79           }
  80       }
  81     else
  82       {
  83         /* Find real component, and adjust source, x and y
  84            accordingly. */
  85
  86         while (true)
  87           {
  88             Component parent = source;
  89
  90             Component child = parent.getComponentAt(x, y);
  91
  92             if (parent == child)
  93               break;
  94
  95             // maybe ignoring would be better?
  96             if (child == null)
  97               {
  98                 String msg = "delivered event not within component. " +
  99                   "Heavyweight source was " + heavySource + ". " +
 100                   "Component was " + parent;
 101                 throw new AWTError(msg);
 102               }
 103             if (child.isLightweight())
 104               {
 105                 // descend down to child
 106                 source = child;
 107                 x -= child.getX();
 108                 y -= child.getY();
 109               }
 110             else
 111               {
 112                 System.err.println("warning: event delivered to wrong " +
 113                                    "heavyweight component. Was " +
 114                                    "delivered to " + source + ". " +
 115                                    "Should have been delivered to " +
 116                                    child + ". Maybe the native window " +
 117                                    "system is bubbling events up the " +
 118                                    "containment hierarchy.");
 119                 break;
 120               }
 121           }
 122
 123         /* ensure that the release event is delivered to the same
 124            component as the press event. For most toolkits this is
 125            only necessary for lightweight components, since the
 126            underlying windowing system takes care of its heavyweight
 127            components. */
 128         if (id == MouseEvent.MOUSE_PRESSED)
 129           releaseTargets[button] = source;
 130       }
 131
 132
 133     if (source == heavySource)
 134       return event; // no change in event
 135
 136     // print warning for heavyweights
 137     /* this warning can safely be removed if a toolkit that
 138        needs heavyweight redirection support is ever created. */
 139     if (!source.isLightweight())
 140       System.err.println("warning: redirecting to heavyweight");
 141
 142     MouseEvent redirected = new MouseEvent(source, event.getID(),
 143                                            event.getWhen(),
 144                                            event.getModifiers(),
 145                                            x, y,
 146                                            event.getClickCount(),
 147                                            event.isPopupTrigger());
 148
 149     return redirected;
 150   }
 151
 152   /**
 153    * Identifies the button number for an input event.
 154    *
 155    * @returns the button number, or 0 if no button modifier was set
 156    * for the event.
 157    */
 158   int getButtonNumber(InputEvent event)
 159   {
 160     int modifiers = event.getModifiers();
 161
 162     modifiers &=
 163       InputEvent.BUTTON1_MASK |
 164       InputEvent.BUTTON2_MASK |
 165       InputEvent.BUTTON3_MASK;
 166
 167     switch (modifiers)
 168       {
 169       case InputEvent.BUTTON1_MASK:
 170         return 1;
 171       case InputEvent.BUTTON2_MASK:
 172         return 2;
 173       case InputEvent.BUTTON3_MASK:
 174         return 3;
 175       case 0:
 176         return 0;
 177
 178       default:
 179         System.err.println("FIXME: multibutton event");
 180         return 0;
 181       }
 182   }
 183 }