Experimental alignment layout manager using a property on the views

ui/views/anchor_attribute.h

+// Copyright (c) 2016 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_VIEWS_ANCHOR_ATTRIBUTE_H_
+#define UI_VIEWS_ANCHOR_ATTRIBUTE_H_
+
+#include "base/macros.h"
+#include "base/set_template.h"
+#include "ui/gfx/geometry/point.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/geometry/size.h"
+#include "ui/views/attributes.h"
+#include "ui/views/fill_attribute.h"
+#include "ui/views/view.h"
+
+namespace views {
+
+enum class Anchor {
+  // Anchor view's left side to the parent's left side of its content bounds.
+  Left,
+  // Anchor view's top side to the parent's top side of its content bounds.
+  Top,
+  // Anchor view's right side to the parent's right side of its content
+  // bounds.
+  Right,
+  // Anchor view's bottom side to the parent's bottom side of its content
+  // bounds.
+  Bottom,
+};
+
+using Anchors = base::SetOf<Anchor, Anchor::Bottom>;
+
+struct VIEWS_EXPORT AnchorContent {
+  AnchorContent();
+  AnchorContent(Anchors anchors);
+  AnchorContent(const AnchorContent& content);
+  static Anchors AnchorFill(Fill fill);
+  gfx::Point& anchorBasis() { return anchor_basis_; }
+  Anchors& anchors() { return anchors_; }
+  gfx::Size& LastParentSize() { return last_parent_size_; }
+  void SetAnchors(Anchors anchors);
+  void SetAttribute(Attribute *attribute) { attribute_ = attribute; }
+  void UpdateAnchorBasis(View *view);
+ private:
+  Attribute *attribute_;
+  Anchors anchors_;
+  gfx::Point anchor_basis_;
+  gfx::Size last_parent_size_;
+};
+
+class VIEWS_EXPORT AnchorAttribute : public CustomAttribute<AnchorContent> {
+ public:
+  AnchorAttribute();
+  AnchorAttribute(Anchors anchors);
+  AnchorAttribute(AnchorContent& content);
+  AttributeId Identity() const override;
+  void Notification(Attribute::NotifyType type, Attribute* attribute) override;
+  void ViewNotification(View *view) override;
+};
+
+REGISTER_ATTRIBUTE_ID(CustomAttribute<AnchorContent>);
+REGISTER_ATTRIBUTE_ID(AnchorAttribute);
+
+} // namespace views
+
+#endif // UI_VIEWS_ANCHOR_ATTRIBUTE_H_