Fixes bug where IViewManagerClient could be messaged unnecessarily

mojo/services/view_manager/root_node_manager.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_SERVICES_VIEW_MANAGER_ROOT_NODE_MANAGER_H_
 #define MOJO_SERVICES_VIEW_MANAGER_ROOT_NODE_MANAGER_H_
 
 #include <map>
 #include <set>
 
@@ skipping 30 matching lines @@
   // Create when a ViewManagerConnection is about to make a change. Ensures
   // clients are notified of the correct change id.
   class ScopedChange {
    public:
     ScopedChange(ViewManagerConnection* connection,
                  RootNodeManager* root,
                  RootNodeManager::ChangeType change_type,
                  bool is_delete_node);
     ~ScopedChange();
 
+    TransportConnectionId connection_id() const { return connection_id_; }
+    ChangeType change_type() const { return change_type_; }
+    bool is_delete_node() const { return is_delete_node_; }
+
+    // Marks the connection with the specified id as having seen a message.
+    void MarkConnectionAsMessaged(TransportConnectionId connection_id) {
+      message_ids_.insert(connection_id);
+    }
+
+    // Returns true if MarkConnectionAsMessaged(connection_id) was invoked.
+    bool DidMessageConnection(TransportConnectionId connection_id) const {
+      return message_ids_.count(connection_id) > 0;
+    }
+
    private:
     RootNodeManager* root_;
+    const TransportConnectionId connection_id_;
     const ChangeType change_type_;
+    const bool is_delete_node_;
+
+    // See description of MarkConnectionAsMessaged/DidMessageConnection.
+    std::set<TransportConnectionId> message_ids_;
 
     DISALLOW_COPY_AND_ASSIGN(ScopedChange);
   };
 
   RootNodeManager(ServiceProvider* service_provider,
                   RootViewManagerDelegate* view_manager_delegate);
   virtual ~RootNodeManager();
 
   // Returns the id for the next ViewManagerConnection.
   TransportConnectionId GetAndAdvanceNextConnectionId();
@@ skipping 17 matching lines @@
   ViewManagerConnection* GetConnection(TransportConnectionId connection_id);
 
   // Returns the Node identified by |id|.
   Node* GetNode(const NodeId& id);
 
   // Returns the View identified by |id|.
   View* GetView(const ViewId& id);
 
   Node* root() { return &root_; }
 
-  bool IsProcessingChange() const { return change_source_ != 0; }
+  bool IsProcessingChange() const { return current_change_ != NULL; }
 
-  bool is_processing_delete_node() const { return is_processing_delete_node_; }
+  bool is_processing_delete_node() const {
+    return current_change_ && current_change_->is_delete_node(); }
+
+  // Invoked when a connection messages a client about the change. This is used
+  // to avoid sending ServerChangeIdAdvanced() unnecessarily.
+  void OnConnectionMessagedClient(TransportConnectionId id);
+
+  // Returns true if OnConnectionMessagedClient() was invoked for id.
+  bool DidConnectionMessageClient(TransportConnectionId id) const;
 
   // These functions trivially delegate to all ViewManagerConnections, which in
   // term notify their clients.
   void ProcessNodeBoundsChanged(const Node* node,
                                 const gfx::Rect& old_bounds,
                                 const gfx::Rect& new_bounds);
   void ProcessNodeHierarchyChanged(const Node* node,
                                    const Node* new_parent,
                                    const Node* old_parent);
   void ProcessNodeViewReplaced(const Node* node,
                                const View* new_view_id,
                                const View* old_view_id);
   void ProcessNodeDeleted(const NodeId& node);
   void ProcessViewDeleted(const ViewId& view);
 
  private:
   // Used to setup any static state needed by RootNodeManager.
   struct Context {
     Context();
     ~Context();
   };
 
   typedef std::map<TransportConnectionId, ViewManagerConnection*> ConnectionMap;
 
-  // Invoked when a particular connection is about to make a change.
-  // Subsequently followed by FinishChange() once the change is done.
+  // Invoked when a connection is about to make a change.  Subsequently followed
+  // by FinishChange() once the change is done.
   //
   // Changes should never nest, meaning each PrepareForChange() must be
   // balanced with a call to FinishChange() with no PrepareForChange()
   // in between.
-  void PrepareForChange(ViewManagerConnection* connection, bool is_delete_node);
+  void PrepareForChange(ScopedChange* change);
 
   // Balances a call to PrepareForChange().
-  void FinishChange(ChangeType change_type);
+  void FinishChange();
 
   // Returns true if the specified connection originated the current change.
   bool IsChangeSource(TransportConnectionId connection_id) const {
-    return connection_id == change_source_;
+    return current_change_ && current_change_->connection_id() == connection_id;
   }
 
   // Implementation of the two connect variants.
   ViewManagerConnection* ConnectImpl(const String& url,
                                      const Array<TransportNodeId>& node_ids);
 
   // Overridden from NodeDelegate:
   virtual void OnNodeHierarchyChanged(const Node* node,
                                       const Node* new_parent,
                                       const Node* old_parent) OVERRIDE;
   virtual void OnNodeViewReplaced(const Node* node,
                                   const View* new_view,
                                   const View* old_view) OVERRIDE;
 
   Context context_;
 
   ServiceProvider* service_provider_;
 
   // ID to use for next ViewManagerConnection.
   TransportConnectionId next_connection_id_;
 
   TransportChangeId next_server_change_id_;
 
   // Set of ViewManagerConnections.
   ConnectionMap connection_map_;
 
-  // If non-zero we're processing a change from this client.
-  TransportConnectionId change_source_;
-
-  // True if we're processing a DeleteNode request.
-  bool is_processing_delete_node_;
-
   RootViewManager root_view_manager_;
 
   // Root node.
   Node root_;
 
   // Set of ViewManagerConnections created by way of Connect(). These have to be
   // explicitly destroyed.
   std::set<ViewManagerConnection*> connections_created_by_connect_;
 
+  // If non-null we're processing a change. The ScopedChange is not owned by us
+  // (it's created on the stack by ViewManagerConnection).
+  ScopedChange* current_change_;
+
   DISALLOW_COPY_AND_ASSIGN(RootNodeManager);
 };
 
 }  // namespace service
 }  // namespace view_manager
 }  // namespace mojo
 
 #endif  // MOJO_SERVICES_VIEW_MANAGER_ROOT_NODE_MANAGER_H_