Added a ptr() method to SGPropertyNode_ptr to get the raw pointer.

Added the SGPropertyChangeListener interface and addChangeListener and
firePropertyChange methods.

simgear/misc/props.cxx

@@ -360,9 +360,15 @@ inline bool
 SGPropertyNode::set_bool (bool val)
 {
   if (_tied) {
-    return _value.bool_val->setValue(val);
+    if (_value.bool_val->setValue(val)) {
+      firePropertyChange();
+      return true;
+    } else {
+      return false;
+    }
   } else {
     _local_val.bool_val = val;
+    firePropertyChange();
     return true;
   }
 }
@@ -371,9 +377,15 @@ inline bool
 SGPropertyNode::set_int (int val)
 {
   if (_tied) {
-    return _value.int_val->setValue(val);
+    if (_value.int_val->setValue(val)) {
+      firePropertyChange();
+      return true;
+    } else {
+      return false;
+    }
   } else {
     _local_val.int_val = val;
+    firePropertyChange();
     return true;
   }
 }
@@ -382,9 +394,15 @@ inline bool
 SGPropertyNode::set_long (long val)
 {
   if (_tied) {
-    return _value.long_val->setValue(val);
+    if (_value.long_val->setValue(val)) {
+      firePropertyChange();
+      return true;
+    } else {
+      return false;
+    }
   } else {
     _local_val.long_val = val;
+    firePropertyChange();
     return true;
   }
 }
@@ -393,9 +411,15 @@ inline bool
 SGPropertyNode::set_float (float val)
 {
   if (_tied) {
-    return _value.float_val->setValue(val);
+    if (_value.float_val->setValue(val)) {
+      firePropertyChange();
+      return true;
+    } else {
+      return false;
+    }
   } else {
     _local_val.float_val = val;
+    firePropertyChange();
     return true;
   }
 }
@@ -404,9 +428,15 @@ inline bool
 SGPropertyNode::set_double (double val)
 {
   if (_tied) {
-    return _value.double_val->setValue(val);
+    if (_value.double_val->setValue(val)) {
+      firePropertyChange();
+      return true;
+    } else {
+      return false;
+    }
   } else {
     _local_val.double_val = val;
+    firePropertyChange();
     return true;
   }
 }
@@ -415,10 +445,16 @@ inline bool
 SGPropertyNode::set_string (const char * val)
 {
   if (_tied) {
-    return _value.string_val->setValue(val);
+    if (_value.string_val->setValue(val)) {
+      firePropertyChange();
+      return true;
+    } else {
+      return false;
+    }
   } else {
     delete [] _local_val.string_val;
     _local_val.string_val = copy_string(val);
+    firePropertyChange();
     return true;
   }
 }
@@ -592,7 +628,8 @@ SGPropertyNode::SGPropertyNode ()
     _type(NONE),
     _tied(false),
     _attr(READ|WRITE),
-    _count(0)
+    _count(0),
+    _listeners(0)
 {
   _local_val.string_val = 0;
 }
@@ -608,7 +645,8 @@ SGPropertyNode::SGPropertyNode (const SGPropertyNode &node)
     _type(node._type),
     _tied(node._tied),
     _attr(node._attr),
-    _count(0)
+    _count(0),
+    _listeners(0)		// CHECK!!
 {
   _name = copy_string(node._name);
   _local_val.string_val = 0;
@@ -690,7 +728,8 @@ SGPropertyNode::SGPropertyNode (const char * name,
     _type(NONE),
     _tied(false),
     _attr(READ|WRITE),
-    _count(0)
+    _count(0),
+    _listeners(0)
 {
   _name = copy_string(name);
   _local_val.string_val = 0;
@@ -705,6 +744,7 @@ SGPropertyNode::~SGPropertyNode ()
   delete [] _name;
   delete _path_cache;
   clear_value();
+  delete _listeners;
 }
 
 
@@ -812,6 +852,8 @@ SGPropertyNode::getChild (const char * name, int index, bool create)
       node = new SGPropertyNode(name, index, this);
     }
     _children.push_back(node);
+    if (_parent != 0)
+      _parent->firePropertyChange();
     return _children[_children.size()-1];
   } else {
     return 0;
@@ -870,6 +912,8 @@ SGPropertyNode::removeChild (const char * name, int index, bool keep)
     node->setAttribute(REMOVED, true);
     ret = node;
   }
+  if (_parent != 0)
+    _parent->firePropertyChange();
   return ret;
 }
 
@@ -1939,6 +1983,26 @@ SGPropertyNode::untie (const char * relative_path)
   return (node == 0 ? false : node->untie());
 }
 
+void
+SGPropertyNode::addChangeListener (SGPropertyChangeListener * listener)
+{
+  if (_listeners == 0)
+    _listeners = new vector<SGPropertyChangeListener *>;
+  _listeners->push_back(listener);
+}
+
+void
+SGPropertyNode::firePropertyChange (SGPropertyNode * node)
+{
+  if (_listeners != 0) {
+    for (int i = 0; i < _listeners->size(); i++) {
+      (*_listeners)[i]->propertyChanged(node);
+    }
+  }
+  if (_parent != 0)
+    _parent->firePropertyChange(node);
+}
+
 
 
 ////////////////////////////////////////////////////////////////////////

simgear/misc/props.hxx

@@ -503,6 +503,11 @@ public:
    */
   operator const SGPropertyNode *() const;
 
+  /**
+   * Return the pointer.
+   */
+  SGPropertyNode * ptr () { return _ptr; }
+
   /**
    * Validity test
    */
@@ -513,6 +518,23 @@ private:
   SGPropertyNode *_ptr;
 };
 
+
+
+/**
+ * The property change listener interface.
+ *
+ * <p>Any class that needs to listen for property changes must implement
+ * this interface.</p>
+ */
+class SGPropertyChangeListener
+{
+public:
+
+  virtual void propertyChanged (SGPropertyNode * node) = 0;
+
+};
+
+
 
 /**
  * A node in a property tree.
@@ -1098,9 +1120,30 @@ public:
   bool untie (const char * relative_path);
 
 
+  /**
+   * Add a change listener to the property.
+   */
+  void addChangeListener (SGPropertyChangeListener * listener);
+
+
+  /**
+   * Fire a property change to all listeners.
+   */
+  void firePropertyChange ()
+  {
+    firePropertyChange(this);
+  }
+
+
 protected:
 
 
+  /**
+   * Fire a property change with an explicit target node.
+   */
+  void firePropertyChange (SGPropertyNode * node);
+
+
   /**
    * Protected constructor for making new nodes on demand.
    */
@@ -1198,6 +1241,8 @@ private:
     char * string_val;
   } _local_val;
 
+  vector <SGPropertyChangeListener *> * _listeners;
+
 
 
   /**