Experimental alignment layout manager using state retained in the layout manager

ui/views/layout/align_layout_state.h

+// Copyright (c) 2011 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_LAYOUT_ALIGN_LAYOUT_STATE_H_
+#define UI_VIEWS_LAYOUT_ALIGN_LAYOUT_STATE_H_
+
+#include <stddef.h>
+
+#include <algorithm>
+#include <initializer_list>
+#include <map>
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "base/macros.h"
+#include "ui/gfx/geometry/point.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/views/align_attribute.h"
+#include "ui/views/anchor_attribute.h"
+#include "ui/views/layout/layout_manager.h"
+#include "ui/views/view.h"
+
+namespace views {
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// AlignLayout
+//  A LayoutManager that causes the associated view's children to be aligned
+//  and/or anchored within the bounds of their parent based on the value of the
+//  views' align or anchor attributes.
+//
+///////////////////////////////////////////////////////////////////////////////
+class VIEWS_EXPORT AlignLayoutState : public LayoutManager {
+ public:
+  AlignLayoutState();
+  ~AlignLayoutState() override;
+
+  // Overridden from LayoutManager:
+  void Installed(View* host) override;
+  void Layout(View* host) override;
+  gfx::Size GetPreferredSize(const View* host) const override;
+  int GetPreferredHeightForWidth(const View* host, int width) const override;
+  void ViewAdded(View* host, View* view) override;
+  void ViewRemoved(View* host, View* view) override;
+
+  void AlignView(View* view, Align align);
+  void AnchorView(View* view, Anchors anchors);
+  void AnchorView(View* view, const std::initializer_list<Anchor>& anchors);
+  void NoAlignView(View* view);
+  void NoAnchorView(View* view);
+
+  void SetViewBounds(View* view, int x, int y, int width, int height);
+
+ private:
+  struct AnchorState {
+    AnchorState();
+    AnchorState(Anchors anchors);
+    AnchorState(const AnchorState& state);
+    ~AnchorState();
+    Anchors anchors;
+    gfx::Point anchor_basis;
+  };
+  using AlignMap = std::map<const View*, Align>;
+  using AnchorMap = std::map<const View*, AnchorState>;
+  void AlignViews(View* host, Align align, gfx::Rect& contents);
+  bool FindAlign(View* view, Align* align);
+  bool FindAlign(const View* view, Align* align) const;
+  bool FindAnchorState(View* view, AnchorState** state);
+  void InternalUpdateAnchorBasis(View* view, AnchorMap::iterator pos);
+  void PlaceView(View* view, Align align, gfx::Rect& contents);
+  bool ShouldAlign(View* host);
+  bool ShouldInsert(View* child1, View* child2, Align align);
+  void UpdateAnchorAlign(View *view, Align align);
+  void UpdateAnchorBasis(View* view);
+  AlignMap align_map_;
+  AnchorMap anchor_map_;
+  gfx::Size last_host_size_;
+  DISALLOW_COPY_AND_ASSIGN(AlignLayoutState);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_LAYOUT_FILL_LAYOUT_STATE_H_