Separate the logic of popup alignment and workarea handling as delegate.

ui/message_center/views/popup_alignment_delegate.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 UI_MESSAGE_CENTER_VIEWS_POPUP_ALIGNMENT_DELEGATE_H_
+#define UI_MESSAGE_CENTER_VIEWS_POPUP_ALIGNMENT_DELEGATE_H_
+
+#include "ui/message_center/message_center_export.h"
+
+namespace gfx {
+class Display;
+class Point;
+class Rect;
+}
+
+namespace message_center {
+
+class MessagePopupCollection;
+
+class MESSAGE_CENTER_EXPORT PopupAlignmentDelegate {
+ public:
+  PopupAlignmentDelegate();
+
+  void set_collection(MessagePopupCollection* collection) {
+    collection_ = collection;
+  }
+
+  // Returns the x-origin for the given toast bounds in the current work area.
+  virtual int GetToastOriginX(const gfx::Rect& toast_bounds) const = 0;
+
+  // Returns the baseline height of the current work area. That is the starting
+  // point if there are no other toasts.
+  virtual int GetBaseLine() const = 0;
+
+  // Returns the height of the bottom of the current work area.
+  virtual int GetWorkAreaBottom() const  = 0;
+
+  // Returns true if the toast should be aligned from top to down.

[stevenjb, 2014/07/02 21:59:24]

s/from top to down/top down/ (or 'from top to bottom')

[Jun Mukai, 2014/07/07 18:12:36]

Done.

+  virtual bool IsTopDown() const = 0;
+
+  // Returns true if the toasts is positioned at the left side of the desktop

[stevenjb, 2014/07/02 21:59:24]

s/toasts is/toasts are/

[Jun Mukai, 2014/07/07 18:12:36]

Done.

+  // so that their reveal animation should happen from left side.
+  virtual bool IsFromLeft() const = 0;
+
+  // Called when a new toast appears or toasts are rearranged in the |display|.
+  // The subclass may override this method to check the current desktop status
+  // so that the toasts are arranged at the right place.

[stevenjb, 2014/07/02 21:59:24]

s/right/correct/ (only because 'right' is ambiguous here since there are lots of
references to left/right)

[Jun Mukai, 2014/07/07 18:12:36]

Done.

+  virtual void RecomputeAlignment(const gfx::Display& display) {}

[stevenjb, 2014/07/02 21:59:23]

nit: It might be better to make this a pure virtual so that each subclass has to
do something here or explicitly do nothing.

[Jun Mukai, 2014/07/07 18:12:36]

Done.

+
+ protected:
+  virtual ~PopupAlignmentDelegate();
+
+  void DoUpdateIfPossible();
+
+ private:
+  MessagePopupCollection* collection_;
+};
+
+}  // namespace message_center
+
+#endif  // UI_MESSAGE_CENTER_VIEWS_POPUP_ALIGNMENT_DELEGATE_H_