Add observers to UndoManager.

Observers are notified when the internal state of UndoManager changes.

BUG=361413

Review URL: https://codereview.chromium.org/231073003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@264001 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 97 insertions, 0 deletions

diff --git a/chrome/browser/undo/undo_manager.cc b/chrome/browser/undo/undo_manager.cc
index 89ffe30..94e28f4 100644
--- a/chrome/browser/undo/undo_manager.cc
+++ b/chrome/browser/undo/undo_manager.cc
@@ -6,6 +6,7 @@
 
 #include "base/auto_reset.h"
 #include "base/logging.h"
+#include "chrome/browser/undo/undo_manager_observer.h"
 #include "chrome/browser/undo/undo_operation.h"
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
@@ -165,6 +166,16 @@ void UndoManager::RemoveAllOperations() {
   DCHECK(!group_actions_count_);
   undo_actions_.clear();
   redo_actions_.clear();
+
+  NotifyOnUndoManagerStateChange();
+}
+
+void UndoManager::AddObserver(UndoManagerObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void UndoManager::RemoveObserver(UndoManagerObserver* observer) {
+  observers_.RemoveObserver(observer);
 }
 
 void UndoManager::Undo(bool* performing_indicator,
@@ -185,6 +196,13 @@ void UndoManager::Undo(bool* performing_indicator,
   StartGroupingActions();
   action->Undo();
   EndGroupingActions();
+
+  NotifyOnUndoManagerStateChange();
+}
+
+void UndoManager::NotifyOnUndoManagerStateChange() {
+  FOR_EACH_OBSERVER(
+      UndoManagerObserver, observers_, OnUndoManagerStateChange());
 }
 
 void UndoManager::AddUndoGroup(UndoGroup* new_undo_group) {
@@ -197,6 +215,8 @@ void UndoManager::AddUndoGroup(UndoGroup* new_undo_group) {
   // Limit the number of undo levels so the undo stack does not grow unbounded.
   if (GetActiveUndoGroup()->size() > kMaxUndoGroups)
     GetActiveUndoGroup()->erase(GetActiveUndoGroup()->begin());
+
+  NotifyOnUndoManagerStateChange();
 }
 
 ScopedVector<UndoGroup>* UndoManager::GetActiveUndoGroup() {
diff --git a/chrome/browser/undo/undo_manager.h b/chrome/browser/undo/undo_manager.h
index d05edc3..443d2d7 100644
--- a/chrome/browser/undo/undo_manager.h
+++ b/chrome/browser/undo/undo_manager.h
@@ -8,8 +8,10 @@
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
+#include "base/observer_list.h"
 #include "base/strings/string16.h"
 
+class UndoManagerObserver;
 class UndoOperation;
 
 // UndoGroup ------------------------------------------------------------------
@@ -83,11 +85,18 @@ class UndoManager {
   // suspension of undo tracking states are left unchanged.
   void RemoveAllOperations();
 
+  // Observers are notified when the internal state of this class changes.
+  void AddObserver(UndoManagerObserver* observer);
+  void RemoveObserver(UndoManagerObserver* observer);
+
  private:
   void Undo(bool* performing_indicator,
             ScopedVector<UndoGroup>* active_undo_group);
   bool is_user_action() const { return !performing_undo_ && !performing_redo_; }
 
+  // Notifies the observers that the undo manager's state has changed.
+  void NotifyOnUndoManagerStateChange();
+
   // Handle the addition of |new_undo_group| to the active undo group container.
   void AddUndoGroup(UndoGroup* new_undo_group);
 
@@ -99,6 +108,9 @@ class UndoManager {
   ScopedVector<UndoGroup> undo_actions_;
   ScopedVector<UndoGroup> redo_actions_;
 
+  // The observers to notify when internal state changes.
+  ObserverList<UndoManagerObserver> observers_;
+
   // Supports grouping operations into a single undo action.
   int group_actions_count_;
 
diff --git a/chrome/browser/undo/undo_manager_observer.h b/chrome/browser/undo/undo_manager_observer.h
new file mode 100644
index 0000000..c61aea2
--- /dev/null
+++ b/chrome/browser/undo/undo_manager_observer.h
@@ -0,0 +1,18 @@
+// 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 CHROME_BROWSER_UNDO_UNDO_MANAGER_OBSERVER_H_
+#define CHROME_BROWSER_UNDO_UNDO_MANAGER_OBSERVER_H_
+
+// Observer for the UndoManager.
+class UndoManagerObserver {
+ public:
+  // Invoked when the internal state of the UndoManager has changed.
+  virtual void OnUndoManagerStateChange() = 0;
+
+ protected:
+  virtual ~UndoManagerObserver() {}
+};
+
+#endif  // CHROME_BROWSER_UNDO_UNDO_MANAGER_OBSERVER_H_
diff --git a/chrome/browser/undo/undo_manager_test.cc b/chrome/browser/undo/undo_manager_test.cc
index 70215d7..4ed7d49 100644
--- a/chrome/browser/undo/undo_manager_test.cc
+++ b/chrome/browser/undo/undo_manager_test.cc
@@ -4,6 +4,7 @@
 
 #include "base/auto_reset.h"
 #include "chrome/browser/undo/undo_manager.h"
+#include "chrome/browser/undo/undo_manager_observer.h"
 #include "chrome/browser/undo/undo_operation.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -95,6 +96,22 @@ void TestUndoService::RecordUndoCall() {
     ++undo_operation_count_;
 }
 
+// TestObserver ----------------------------------------------------------------
+
+class TestObserver : public UndoManagerObserver {
+ public:
+  TestObserver() : state_change_count_(0) {}
+  // Returns the number of state change callbacks
+  int state_change_count() { return state_change_count_; }
+
+  virtual void OnUndoManagerStateChange() OVERRIDE { ++state_change_count_; }
+
+ private:
+  int state_change_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestObserver);
+};
+
 // Tests -----------------------------------------------------------------------
 
 TEST(UndoServiceTest, AddUndoActions) {
@@ -216,4 +233,34 @@ TEST(UndoServiceTest, GetAllUndoOperations) {
   EXPECT_EQ(4U, all_operations.size());
 }
 
+TEST(UndoServiceTest, ObserverCallbacks) {
+  TestObserver observer;
+  TestUndoService undo_service;
+  undo_service.undo_manager_.AddObserver(&observer);
+  EXPECT_EQ(0, observer.state_change_count());
+
+  undo_service.TriggerOperation();
+  EXPECT_EQ(1, observer.state_change_count());
+
+  undo_service.undo_manager_.StartGroupingActions();
+  undo_service.TriggerOperation();
+  undo_service.TriggerOperation();
+  undo_service.undo_manager_.EndGroupingActions();
+  EXPECT_EQ(2, observer.state_change_count());
+
+  // There should be at least 1 observer callback for undo.
+  undo_service.undo_manager_.Undo();
+  int callback_count_after_undo = observer.state_change_count();
+  EXPECT_GT(callback_count_after_undo, 2);
+
+  // There should be at least 1 observer callback for redo.
+  undo_service.undo_manager_.Redo();
+  int callback_count_after_redo = observer.state_change_count();
+  EXPECT_GT(callback_count_after_redo, callback_count_after_undo);
+
+  undo_service.undo_manager_.RemoveObserver(&observer);
+  undo_service.undo_manager_.Undo();
+  EXPECT_EQ(callback_count_after_redo, observer.state_change_count());
+}
+
 } // namespace