diff --git a/src/GUI/dialog.hxx b/src/GUI/dialog.hxx
index de2e900a9..4b4752d16 100644
--- a/src/GUI/dialog.hxx
+++ b/src/GUI/dialog.hxx
@@ -1,4 +1,4 @@
-// dialog.hxx - XML-configurable dialog box.
+// dialog.hxx - XML-configured dialog box.
 
 #ifndef __DIALOG_HXX
 #define __DIALOG_HXX 1
@@ -20,28 +20,25 @@ class FGBinding;
 
 
 /**
- * PUI userdata describing a GUI object.
- */
-struct GUIInfo
-{
-    GUIInfo (FGDialog * w);
-    virtual ~GUIInfo ();
-    
-    FGDialog * widget;
-    vector <FGBinding *> bindings;
-};
-
-
-/**
- * Top-level GUI widget.
+ * An XML-configured dialog box.
+ *
+ * The GUI manager stores only the property tree for the dialog
+ * boxes.  This class creates a PUI dialog box on demand from
+ * the properties in that tree.  The manager recreates the dialog
+ * every time it needs to show it.
  */
 class FGDialog
 {
 public:
 
-
     /**
      * Construct a new GUI widget configured by a property tree.
+     *
+     * The configuration properties are not part of the main
+     * FlightGear property tree; the GUI manager reads them
+     * from individual configuration files.
+     *
+     * @param props A property tree describing the dialog.
      */
     FGDialog (SGPropertyNode_ptr props);
 
@@ -55,7 +52,8 @@ public:
     /**
      * Update the values of all GUI objects with a specific name.
      *
-     * This method copies from the property to the GUI object.
+     * This method copies values from the FlightGear property tree to
+     * the GUI object(s).
      *
      * @param objectName The name of the GUI object(s) to update.
      *        Use the empty name for all unnamed objects.
@@ -66,7 +64,8 @@ public:
     /**
      * Apply the values of all GUI objects with a specific name.
      *
-     * This method copies from the GUI object to the property.
+     * This method copies values from the GUI object(s) to the
+     * FlightGear property tree.
      *
      * @param objectName The name of the GUI object(s) to update.
      *        Use the empty name for all unnamed objects.
@@ -77,7 +76,8 @@ public:
     /**
      * Update the values of all GUI objects.
      *
-     * This method copies from the properties to the GUI objects.
+     * This method copies values from the FlightGear property tree to
+     * the GUI objects.
      */
     virtual void updateValues ();
 
@@ -85,23 +85,39 @@ public:
     /**
      * Apply the values of all GUI objects.
      *
-     * This method copies from the GUI objects to the properties.
+     * This method copies from the GUI objects to the FlightGear
+     * property tree properties.
      */
     virtual void applyValues ();
 
 
 private:
-    FGDialog (const FGDialog &); // just for safety
 
+    // Private copy constructor to avoid unpleasant surprises.
+    FGDialog (const FGDialog &);
+
+    // Show the dialog.
     void display (SGPropertyNode_ptr props);
+
+    // Build the dialog or a subobject of it.
     puObject * makeObject (SGPropertyNode * props,
                            int parentWidth, int parentHeight);
+
+    // Common configuration for all GUI objects.
     void setupObject (puObject * object, SGPropertyNode * props);
+
+    // Common configuration for all GUI group objects.
     void setupGroup (puGroup * group, SGPropertyNode * props,
                      int width, int height, bool makeFrame = false);
 
+    // The top-level PUI object.
     puObject * _object;
-    vector<GUIInfo *> _info;
+
+    // PUI provides no way for userdata to be deleted automatically
+    // with a GUI object, so we have to keep track of all the special
+    // data we allocated and then free it manually when the dialog
+    // closes.
+    vector<void *> _info;
     struct PropertyObject {
         PropertyObject (const char * name,
                         puObject * object,
@@ -111,6 +127,12 @@ private:
         SGPropertyNode_ptr node;
     };
     vector<PropertyObject *> _propertyObjects;
+
+    // PUI doesn't copy arrays, so we have to allocate string arrays
+    // and then keep pointers so that we can delete them when the
+    // dialog closes.
+    char ** make_char_array (int size);
+    vector<char **> _char_arrays;
 };
 
 #endif // __DIALOG_HXX