Multi-tab: Adding new Notification when tab selection changes (again).

chrome/browser/tabs/tab_strip_model_observer.h

 // Copyright (c) 2011 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 CHROME_BROWSER_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 #define CHROME_BROWSER_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 #pragma once
 
 class TabContentsWrapper;
 class TabStripModel;
+class TabStripSelectionModel;
 
 ////////////////////////////////////////////////////////////////////////////////
 //
 // TabStripModelObserver
 //
 //  Objects implement this interface when they wish to be notified of changes
 //  to the TabStripModel.
 //
 //  Two major implementers are the TabStrip, which uses notifications sent
 //  via this interface to update the presentation of the strip, and the Browser
@@ skipping 33 matching lines @@
   // The specified TabContents at |index| is being detached, perhaps to be
   // inserted in another TabStripModel. The implementer should take whatever
   // action is necessary to deal with the TabContents no longer being present.
   virtual void TabDetachedAt(TabContentsWrapper* contents, int index);
 
   // The active TabContents is about to change from |old_contents|.
   // This gives observers a chance to prepare for an impending switch before it
   // happens.
   virtual void TabDeactivated(TabContentsWrapper* contents);
 
-  // Sent when the selection changes. The previously selected tab is identified
-  // by |old_contents| and the newly selected tab by |new_contents|. |index| is
-  // the index of |new_contents|. When using multiple selection this may be sent
-  // even when the active tab has not changed. For example, if the selection is
-  // extended this method is invoked to inform observers the selection has
-  // changed, but |old_contents| and |new_contents| are the same.  If you only
-  // care about when the active tab changes, check for when |old_contents|
-  // differs from |new_contents|. |user_gesture| specifies whether or not this
+  // Sent when the active tab changes. The previously active tab is identified
+  // by |old_contents| and the newly active tab by |new_contents|. |index| is
+  // the index of |new_contents|. |user_gesture| specifies whether or not this
   // was done by a user input event (e.g. clicking on a tab, keystroke) or as a
   // side-effect of some other function.
-  //
-  // TODO(dpapad): Add TabSelectionChanged method for when the selected tabs
-  // change.
+  // Note: It is possible for the selection to change while the active tab
+  // remains unchanged. For example, control-click may not change the active tab
+  // but does change the selection. In this case |ActiveTabChanged| is not sent.
+  // If you care about any changes to the selection, override
+  // TabSelectionChanged.
   virtual void ActiveTabChanged(TabContentsWrapper* old_contents,
                                 TabContentsWrapper* new_contents,
                                 int index,
                                 bool user_gesture);
 
+  // Sent when the selection changes. More precisely when selected tabs, anchor
+  // tab or active tab change. |old_model| is a snapshot of the selection model
+  // before the change. See also ActiveTabChanged for details.
+  virtual void TabSelectionChanged(const TabStripSelectionModel& old_model);
+
   // The specified TabContents at |from_index| was moved to |to_index|.
   virtual void TabMoved(TabContentsWrapper* contents,
                         int from_index,
                         int to_index);
 
   // The specified TabContents at |index| changed in some way. |contents| may
   // be an entirely different object and the old value is no longer available
   // by the time this message is delivered.
   //
   // See TabChangeType for a description of |change_type|.
@@ skipping 35 matching lines @@
 
   // Invoked when an active/selected tab at |index| is selected again (ie - the
   // active/foreground tab is clicked).
   virtual void ActiveTabClicked(int index);
 
  protected:
   virtual ~TabStripModelObserver() {}
 };
 
 #endif  // CHROME_BROWSER_TABS_TAB_STRIP_MODEL_OBSERVER_H_