BoxLayout now suports per-view margins.

ui/views/layout/box_layout.h

 // 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.
 
 #ifndef UI_VIEWS_LAYOUT_BOX_LAYOUT_H_
 #define UI_VIEWS_LAYOUT_BOX_LAYOUT_H_
 
 #include <map>
 
 #include "base/compiler_specific.h"
@@ skipping 87 matching lines @@
   void SetDefaultFlex(int default_flex);
 
   // Overridden from views::LayoutManager:
   void Installed(View* host) override;
   void ViewRemoved(View* host, View* view) override;
   void Layout(View* host) override;
   gfx::Size GetPreferredSize(const View* host) const override;
   int GetPreferredHeightForWidth(const View* host, int width) const override;
 
  private:
+  // This struct is used internally to "wrap" a child view in order to obviate
+  // the need for the main layout logic to be aware of the per-view margins.
+  // Since each view is a rectangle of a certain size, this wrapper, coupled
+  // with any margins set will increase the apparent size of the view. All
+  // necessary view size/position methods required for the layout logic add or
+  // subtract the margins where appropriate to ensure the actual visible size
+  // of the view doesn't include the margins.
+  struct ViewWrapper {
+    ViewWrapper();
+    ViewWrapper(View* view);
+    ViewWrapper(const ViewWrapper& wrapper) = delete;
+    ~ViewWrapper();
+    int GetHeightForWidth(int width) const;
+    gfx::Size GetPreferredSize() const;
+    void SetBoundsRect(const gfx::Rect& bounds);
+    View* view() const { return view_; }
+    bool visible() const;
+
+   private:
+    View* view_;
+    gfx::Insets margins_;
+  };
+
+  using FlexMap = std::map<const View*, int>;
+
   // Returns the flex for the specified |view|.
   int GetFlexForView(const View* view) const;
 
   // Returns the size and position along the main axis of |rect|.
   int MainAxisSize(const gfx::Rect& rect) const;
   int MainAxisPosition(const gfx::Rect& rect) const;
 
   // Sets the size and position along the main axis of |rect|.
   void SetMainAxisSize(int size, gfx::Rect* rect) const;
   void SetMainAxisPosition(int position, gfx::Rect* rect) const;
 
   // Returns the size and position along the cross axis of |rect|.
   int CrossAxisSize(const gfx::Rect& rect) const;
   int CrossAxisPosition(const gfx::Rect& rect) const;
 
   // Sets the size and position along the cross axis of |rect|.
   void SetCrossAxisSize(int size, gfx::Rect* rect) const;
   void SetCrossAxisPosition(int size, gfx::Rect* rect) const;
 
   // Returns the main axis size for the given view. |child_area_width| is needed
   // to calculate the height of the view when the orientation is vertical.
-  int MainAxisSizeForView(const View* view, int child_area_width) const;
+  int MainAxisSizeForView(const ViewWrapper& view, int child_area_width) const;
 
   // Returns the cross axis size for the given view.
-  int CrossAxisSizeForView(const View* view) const;
+  int CrossAxisSizeForView(const ViewWrapper& view) const;
 
   // The preferred size for the dialog given the width of the child area.
   gfx::Size GetPreferredSizeForChildWidth(const View* host,
                                           int child_area_width) const;
 
   // The amount of space the layout requires in addition to any space for the
   // child views.
   gfx::Size NonChildSize(const View* host) const;
 
   const Orientation orientation_;
 
   // Spacing between child views and host view border.
   gfx::Insets inside_border_insets_;
 
   // Spacing to put in between child views.
   const int between_child_spacing_;
 
   // The alignment of children in the main axis. This is
   // MAIN_AXIS_ALIGNMENT_START by default.
   MainAxisAlignment main_axis_alignment_;
 
   // The alignment of children in the cross axis. This is
   // CROSS_AXIS_ALIGNMENT_STRETCH by default.
   CrossAxisAlignment cross_axis_alignment_;
 
   // A map of views to their flex weights.
-  std::map<const View*, int> flex_map_;
+  FlexMap flex_map_;
 
   // The flex weight for views if none is set. Defaults to 0.
   int default_flex_;
 
   // The minimum cross axis size for the layout.
   int minimum_cross_axis_size_;
 
   // The view that this BoxLayout is managing the layout for.
   views::View* host_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(BoxLayout);
 };
 
 } // namespace views
 
 #endif  // UI_VIEWS_LAYOUT_BOX_LAYOUT_H_