Add ViewObserver to View for view updates

ui/views/view.cc

Index: ui/views/view.cc
diff --git a/ui/views/view.cc b/ui/views/view.cc
index b6cd9d0e97f9345128f754a62f0b80e15fa2430f..596fbf9863c3e05de8801420f0e5a19fe1e0013b 100644
--- a/ui/views/view.cc
+++ b/ui/views/view.cc
@@ -51,6 +51,7 @@
 #include "ui/views/drag_controller.h"
 #include "ui/views/focus/view_storage.h"
 #include "ui/views/layout/layout_manager.h"
+#include "ui/views/view_observer.h"
 #include "ui/views/views_delegate.h"
 #include "ui/views/widget/native_widget_private.h"
 #include "ui/views/widget/root_view.h"
@@ -220,6 +221,8 @@ void View::AddChildViewAt(View* view, int index) {
 
   if (layout_manager_.get())
     layout_manager_->ViewAdded(this, view);
+
+  NotifyViewParentChanged(view, nullptr, this);
 }
 
 void View::ReorderChildView(View* view, int index) {
@@ -247,6 +250,9 @@ void View::ReorderChildView(View* view, int index) {
   InitFocusSiblings(view, index);
   children_.insert(children_.begin() + index, view);
 
+  for (ViewObserver& observer : observers_)
+    observer.OnChildViewReordered(view, index);

[sky, 2016/11/21 16:33:37]

Is index really useful for this notification?

[Sarmad Hashmi, 2016/11/21 17:09:53]

Avoids looking up where the view was placed after being reordered. Removed for
now.

+
   ReorderLayers();
 }
 
@@ -298,6 +304,9 @@ void View::SetBoundsRect(const gfx::Rect& bounds) {
   gfx::Rect prev = bounds_;
   bounds_ = bounds;
   BoundsChanged(prev);
+
+  for (ViewObserver& observer : observers_)
+    observer.OnViewBoundsChanged(this);
 }
 
 void View::SetSize(const gfx::Size& size) {
@@ -418,6 +427,9 @@ void View::SetVisible(bool visible) {
       parent_->NotifyAccessibilityEvent(ui::AX_EVENT_CHILDREN_CHANGED, false);
     }
 
+    for (ViewObserver& observer : observers_)
+      observer.OnViewVisibilityChanged(this);
+
     // This notifies all sub-views recursively.
     PropagateVisibilityNotifications(this, visible_);
     UpdateLayerVisibility();
@@ -436,6 +448,10 @@ void View::SetEnabled(bool enabled) {
   if (enabled != enabled_) {
     enabled_ = enabled;
     AdvanceFocusIfNecessary();
+
+    for (ViewObserver& observer : observers_)
+      observer.OnViewEnabledChanged(this);

[sky, 2016/11/21 16:33:37]

I mildly favor calling this after OnEnabledChanged. That better matches other
places you're notifying observers.

[Sarmad Hashmi, 2016/11/21 17:09:53]

Done.

+
     OnEnabledChanged();
   }
 }
@@ -1364,6 +1380,27 @@ int View::GetLineScrollIncrement(ScrollView* scroll_view,
   return 0;
 }
 
+// Observers -------------------------------------------------------------------

[sky, 2016/11/21 16:33:37]

No need for this comment, please remove.

[Sarmad Hashmi, 2016/11/21 17:09:53]

Done.

+void View::AddObserver(ViewObserver* observer) {
+  CHECK(observer);
+  observers_.AddObserver(observer);
+}
+
+void View::RemoveObserver(ViewObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+bool View::HasObserver(const ViewObserver* observer) const {
+  return observers_.HasObserver(observer);
+}
+
+void View::NotifyViewParentChanged(View* view,
+                                   View* old_parent,
+                                   View* new_parent) {
+  for (ViewObserver& observer : observers_)
+    observer.OnViewParentChanged(view, old_parent, new_parent);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // View, protected:
 
@@ -1839,6 +1876,8 @@ void View::DoRemoveChildView(View* view,
 
   if (layout_manager_)
     layout_manager_->ViewRemoved(this, view);
+
+  NotifyViewParentChanged(view, this, nullptr);

[sky, 2016/11/21 16:33:37]

DoRemoveChildView is called from AddChildView. So, notifying here is wrong in
some cases. Please add test coverage of this case, e.g. adding when a view
already has a parent.

[Sarmad Hashmi, 2016/11/21 17:09:53]

Already have this under the ViewParentChanged test.

[sky, 2016/11/21 18:32:12]

Sure, but your test is verifying the observer is called with a null parent, then
a new parent. It should ensure only one change is observed with the new parent.

 }
 
 void View::PropagateRemoveNotifications(View* old_parent, View* new_parent) {