Make code path for bounds changes getting to renderer less brittle

content/browser/web_contents/web_contents_view_aura.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/web_contents/web_contents_view_aura.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 635 matching lines @@
   bool need_paint_update_;
 
   DISALLOW_COPY_AND_ASSIGN(OverscrollNavigationOverlay);
 };
 
 class WebContentsViewAura::WindowObserver
     : public aura::WindowObserver, public aura::RootWindowObserver {
  public:
   explicit WindowObserver(WebContentsViewAura* view)
       : view_(view),
-        parent_(NULL) {
+        top_level_(NULL) {
     view_->window_->AddObserver(this);
   }
 
   virtual ~WindowObserver() {
     view_->window_->RemoveObserver(this);
     if (view_->window_->GetDispatcher())
       view_->window_->GetDispatcher()->RemoveRootWindowObserver(this);
-    if (parent_)
-      parent_->RemoveObserver(this);
+    if (top_level_)
+      top_level_->RemoveObserver(this);
   }
 
   // Overridden from aura::WindowObserver:
   virtual void OnWindowParentChanged(aura::Window* window,
                                      aura::Window* parent) OVERRIDE {
-    if (window == parent_)
+    if (window == top_level_)
       return;
-    if (parent_)
-      parent_->RemoveObserver(this);
-    parent_ = parent;
-    if (parent)
-      parent->AddObserver(this);
+
+    if (top_level_) {
+      top_level_->RemoveObserver(this);
+      top_level_ = NULL;
+    }
+
+    if (window && window != window->GetToplevelWindow())
+      top_level_ = window->GetToplevelWindow();
+    if (top_level_)
+      top_level_->AddObserver(this);
   }
 
   virtual void OnWindowBoundsChanged(aura::Window* window,
                                      const gfx::Rect& old_bounds,
                                      const gfx::Rect& new_bounds) OVERRIDE {
     SendScreenRects();

[sadrul, 2013/10/31 20:27:05]

As I think about it, this needs to be invoked whenever the bounds of the window
changes in screen coordinate, right? If that is the case, then this should
really be watching all the ancestor windows for the bounds-changed signal. So
not just |parent|, and not just |top-level|. I don't know if there's a better
way of doing that.

[sky, 2013/10/31 21:55:30]

I think you're right. We have something like this in View. See
NeedsNotificationWhenVisibleBoundsChange.

     if (view_->touch_editable_)
       view_->touch_editable_->UpdateEditingController();
   }
 
   virtual void OnWindowAddedToRootWindow(aura::Window* window) OVERRIDE {
-    if (window != parent_)
+    if (window != top_level_)
       window->GetDispatcher()->AddRootWindowObserver(this);
   }
 
   virtual void OnWindowRemovingFromRootWindow(aura::Window* window) OVERRIDE {
-    if (window != parent_)
+    if (window != top_level_)
       window->GetDispatcher()->RemoveRootWindowObserver(this);
   }
 
   // Overridden RootWindowObserver:
   virtual void OnRootWindowHostMoved(const aura::RootWindow* root,
                                      const gfx::Point& new_origin) OVERRIDE {
     // This is for the desktop case (i.e. Aura desktop).
     SendScreenRects();
   }
 
  private:
   void SendScreenRects() {
     RenderWidgetHostImpl::From(view_->web_contents_->GetRenderViewHost())->
         SendScreenRects();
   }
 
   WebContentsViewAura* view_;
 
-  // We cache the old parent so that we can unregister when it's not the parent
-  // anymore.
-  aura::Window* parent_;
+  // We cache the old value so that we can unregister the observer when it
+  // changes. This also allows for filtering the events seen by the observer.
+  aura::Window* top_level_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowObserver);
 };
 
 #if defined(OS_WIN)
 // Constrained windows are added as children of the WebContent's view which may
 // overlap with windowed NPAPI plugins. In that case, tell the RWHV so that it
 // can update the plugins' cutout rects accordingly.
 class WebContentsViewAura::ChildWindowObserver : public aura::WindowObserver,
                                                  public WebContentsObserver {
@@ skipping 920 matching lines @@
       event.location(),
       gfx::Screen::GetScreenFor(GetNativeView())->GetCursorScreenPoint(),
       ConvertAuraEventFlagsToWebInputEventModifiers(event.flags()));
   if (drag_dest_delegate_)
     drag_dest_delegate_->OnDrop();
   current_drop_data_.reset();
   return current_drag_op_;
 }
 
 }  // namespace content