* Fix Mantis 761 (linking and delinking prims rapidly caused prims to 'disappear')

* Root cause was that if two updates occurred in the same second of time, the second one was never sent
* Linking/delinking appears to be okay now

OpenSim/Region/Environment/Scenes/InnerScene.cs

@@ -206,6 +206,12 @@ namespace OpenSim.Region.Environment.Scenes
             }
         }
 
+        /// <summary>
+        /// Add an entity to the list of prims to process on the next update
+        /// </summary>
+        /// <param name="obj">
+        /// A <see cref="EntityBase"/>
+        /// </param>
         internal void AddToUpdateList(EntityBase obj)
         {
             lock (m_updateList)

OpenSim/Region/Environment/Scenes/Scene.cs

@@ -614,7 +614,7 @@ namespace OpenSim.Region.Environment.Scenes
         }
 
         /// <summary>
-        /// 
+        /// Start the timer which triggers regular scene updates
         /// </summary>
         public void StartTimer()
         {

OpenSim/Region/Environment/Scenes/SceneObjectGroup.cs

@@ -247,9 +247,11 @@ namespace OpenSim.Region.Environment.Scenes
         public SceneObjectGroup(Scene scene, ulong regionHandle, SceneObjectPart part)
         {
             m_scene = scene;
+            
             part.SetParent(this);
             part.ParentID = 0;
             part.LinkNum = 0;
+            
             m_parts.Add(part.UUID, part);
 
             SetPartAsRoot(part);
@@ -691,7 +693,7 @@ namespace OpenSim.Region.Environment.Scenes
         #region Scheduling
 
         /// <summary>
-        /// 
+        /// Examine this object's parts to see if they've changed sufficiently to warrant an update
         /// </summary>
         public override void Update()
         {
@@ -703,6 +705,7 @@ namespace OpenSim.Region.Environment.Scenes
                 }
                 lastPhysGroupPos = AbsolutePosition;
             }
+            
             if ((Math.Abs(lastPhysGroupRot.W - GroupRotation.W) > 0.1)
                 || (Math.Abs(lastPhysGroupRot.X - GroupRotation.X) > 0.1)
                 || (Math.Abs(lastPhysGroupRot.Y - GroupRotation.Y) > 0.1)
@@ -714,6 +717,7 @@ namespace OpenSim.Region.Environment.Scenes
                 }
                 lastPhysGroupRot = GroupRotation;
             }
+            
             foreach (SceneObjectPart part in m_parts.Values)
             {
                 part.SendScheduledUpdates();
@@ -737,7 +741,7 @@ namespace OpenSim.Region.Environment.Scenes
         }
 
         /// <summary>
-        /// 
+        /// Schedule a full update for every part in this object
         /// </summary>
         public void ScheduleGroupForFullUpdate()
         {
@@ -910,6 +914,7 @@ namespace OpenSim.Region.Environment.Scenes
             linkPart.RotationOffset = new LLQuaternion(newRot.x, newRot.y, newRot.z, newRot.w);
             
             linkPart.ParentID = m_rootPart.LocalId;
+            
             linkPart.LinkNum = m_parts.Count;
             
             m_parts.Add(linkPart.UUID, linkPart);
@@ -1715,6 +1720,9 @@ namespace OpenSim.Region.Environment.Scenes
             m_scene.EventManager.TriggerGroupGrab(UUID, offsetPos, remoteClient.AgentId);
         }
 
+        /// <summary>
+        /// Completely delete this group and tell all the scene presences about that deletion.
+        /// </summary>
         public void DeleteGroup()
         {
             DetachFromBackup(this);

OpenSim/Region/Environment/Scenes/SceneObjectPart.cs

@@ -132,7 +132,12 @@ namespace OpenSim.Region.Environment.Scenes
         [XmlIgnore] public uint TimeStampLastActivity = 0; // Will be used for AutoReturn
 
         /// <summary>
-        /// Only used internally to schedule client updates
+        /// Only used internally to schedule client updates.
+        /// 0 - no update is scheduled
+        /// 1 - terse update scheduled
+        /// 2 - full update scheduled
+        /// 
+        /// TODO - This should be an enumeration
         /// </summary>
         private byte m_updateFlag;
 
@@ -1090,7 +1095,7 @@ namespace OpenSim.Region.Environment.Scenes
         #region Update Scheduling
 
         /// <summary>
-        /// 
+        /// Clear all pending updates
         /// </summary>
         private void ClearUpdateSchedule()
         {
@@ -1098,7 +1103,7 @@ namespace OpenSim.Region.Environment.Scenes
         }
 
         /// <summary>
-        /// 
+        /// Schedules this prim for a full update
         /// </summary>
         public void ScheduleFullUpdate()
         {
@@ -1107,6 +1112,7 @@ namespace OpenSim.Region.Environment.Scenes
                 m_parentGroup.HasGroupChanged = true;
                 m_parentGroup.QueueForUpdateCheck();
             }
+            
             TimeStampFull = (uint) Util.UnixTimeSinceEpoch();
             m_updateFlag = 2;
         }
@@ -1156,7 +1162,7 @@ namespace OpenSim.Region.Environment.Scenes
         }
 
         /// <summary>
-        /// 
+        /// Tell all the prims which have had updates scheduled 
         /// </summary>
         public void SendScheduledUpdates()
         {
@@ -1689,6 +1695,9 @@ namespace OpenSim.Region.Environment.Scenes
 
         #region Client Update Methods
         
+        /// <summary>
+        /// Tell all scene presences that they should send updates for this part to their clients
+        /// </summary>
         public void AddFullUpdateToAllAvatars()
         {
             List<ScenePresence> avatars = m_parentGroup.GetScenePresences();
@@ -1697,6 +1706,7 @@ namespace OpenSim.Region.Environment.Scenes
                 avatars[i].QueuePartForUpdate(this);
             }
         }
+
         public void SendFullUpdateToAllClientsExcept(LLUUID agentID)
         {
             List<ScenePresence> avatars = m_parentGroup.GetScenePresences();
@@ -1710,6 +1720,8 @@ namespace OpenSim.Region.Environment.Scenes
                 }
             }
         }
+    
+
         public void AddFullUpdateToAvatar(ScenePresence presence)
         {
             presence.QueuePartForUpdate(this);

OpenSim/Region/Environment/Scenes/ScenePresence.cs

@@ -418,6 +418,10 @@ namespace OpenSim.Region.Environment.Scenes
 
         #endregion
 
+        /// <summary>
+        /// Add the part to the queue of parts for which we need to send an update to the client
+        /// </summary>
+        /// <param name="part"></param>
         public void QueuePartForUpdate(SceneObjectPart part)
         {
             //if (InterestList.Contains(part.ParentGroup))
@@ -434,6 +438,11 @@ namespace OpenSim.Region.Environment.Scenes
             return m_scene.PermissionsMngr.GenerateClientFlags(m_uuid, ObjectID);
         }
 
+        /// <summary>
+        /// Send updates to the client about prims which have been placed on the update queue.  We don't 
+        /// necessarily send updates for all the parts on the queue, e.g. if an updates with a more recent
+        /// timestamp has already been sent.
+        /// </summary>
         public void SendPrimUpdates()
         {
             // if (m_scene.QuadTree.GetNodeID(this.AbsolutePosition.X, this.AbsolutePosition.Y) != m_currentQuadNode)
@@ -447,12 +456,11 @@ namespace OpenSim.Region.Environment.Scenes
             {
                 if (!m_isChildAgent || m_scene.m_seeIntoRegionFromNeighbor)
                 {                    
-                    
                     m_scene.SendAllSceneObjectsToClient(this);
                     m_gotAllObjectsInScene = true;                    
-                    
                 }
             }
+            
             if (m_partsUpdateQueue.Count > 0)
             {
                 bool runUpdate = true;
@@ -465,16 +473,18 @@ namespace OpenSim.Region.Environment.Scenes
                         ScenePartUpdate update = m_updateTimes[part.UUID];
 
                         // Two updates can occur with the same timestamp (especially
-                        // since our timestamp resolution is to the nearest second).  The first
+                        // since our timestamp resolution is to the nearest second).  Therefore, we still need
-                        // could have been sent in the last update - we still need to send the 
+                        // to send an update even if the last full update time is identical to the part's 
-                        // second here.
+                        // update timestamp.
-
+                        //
-                        if (update.LastFullUpdateTime < part.TimeStampFull)
+                        // If we don't do this, various events (such as linking and delinking in the same
+                        // second), will stop working properly!
+                        if (update.LastFullUpdateTime <= part.TimeStampFull)
                         {
                             //need to do a full update
                             part.SendFullUpdate(ControllingClient, GenerateClientFlags(part.UUID));
 
-                            // We'll update to the part's timestamp rather than the current to 
+                            // We'll update to the part's timestamp rather than the current time to 
                             // avoid the race condition whereby the next tick occurs while we are
                             // doing this update.  If this happened, then subsequent updates which occurred
                             // on the same tick or the next tick of the last update would be ignored.