Add main axis alignment for BoxLayout.

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 "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/gfx/insets.h"
 #include "ui/views/layout/layout_manager.h"
 
 namespace gfx {
+class Rect;
 class Size;
 }
 
 namespace views {
 
 class View;
 
 // A Layout manager that arranges child views vertically or horizontally in a
 // side-by-side fashion with spacing around and between the child views. The
 // child views are always sized according to their preferred size. If the
 // host's bounds provide insufficient space, child views will be clamped.
 // Excess space will not be distributed.
 class VIEWS_EXPORT BoxLayout : public LayoutManager {
  public:
   enum Orientation {
     kHorizontal,
     kVertical,
   };
 
+  // This specifies where along the main axis the children should be laid out.
+  // e.g. a horizontal layout of MAIN_AXIS_ALIGNMENT_END will result in the
+  // child views being right-aligned.
+  enum MainAxisAlignment {
+    MAIN_AXIS_ALIGNMENT_START,
+    MAIN_AXIS_ALIGNMENT_CENTER,
+    MAIN_AXIS_ALIGNMENT_END,
+
+    // This distributes extra space among the child views. This increases the
+    // size of child views along the main axis rather than the space between
+    // them.
+    MAIN_AXIS_ALIGNMENT_FILL,
+    // TODO(calamity): Add MAIN_AXIS_ALIGNMENT_JUSTIFY which spreads blank space
+    // in-between the child views.
+  };
+
+  // TODO(calamity): Add CrossAxisAlignment property to allow cross axis
+  // alignment.
+
   // Use |inside_border_horizontal_spacing| and
   // |inside_border_vertical_spacing| to add additional space between the child
   // view area and the host view border. |between_child_spacing| controls the
   // space in between child views.
   BoxLayout(Orientation orientation,
             int inside_border_horizontal_spacing,
             int inside_border_vertical_spacing,
             int between_child_spacing);
   virtual ~BoxLayout();
 
-  void set_spread_blank_space(bool spread) {
-    spread_blank_space_ = spread;
+  void set_main_axis_alignment(MainAxisAlignment main_axis_alignment) {
+    main_axis_alignment_ = main_axis_alignment;
   }
 
   // Overridden from views::LayoutManager:
   virtual void Layout(View* host) OVERRIDE;
   virtual gfx::Size GetPreferredSize(View* host) OVERRIDE;
   virtual int GetPreferredHeightForWidth(View* host, int width) OVERRIDE;
 
  private:
+  // Returns the size and position along the main axis of |child_area|.
+  int MainAxisSize(const gfx::Rect& child_area) const;
+  int MainAxisPosition(const gfx::Rect& child_area) const;
+
+  // Sets the size and position along the main axis of |child_area|.
+  void SetMainAxisSize(int size, gfx::Rect* child_area) const;
+  void SetMainAxisPosition(int position, gfx::Rect* child_area) const;
+
   // The preferred size for the dialog given the width of the child area.
   gfx::Size GetPreferredSizeForChildWidth(View* host, int child_area_width);
 
   // The amount of space the layout requires in addition to any space for the
   // child views.
   gfx::Size NonChildSize(View* host);
 
   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_;
 
-  // Whether the available extra space should be distributed among the child
-  // views.
-  bool spread_blank_space_;
+  // The alignment of children in the main axis. This is
+  // MAIN_AXIS_ALIGNMENT_START by default.
+  MainAxisAlignment main_axis_alignment_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(BoxLayout);
 };
 
 } // namespace views
 
 #endif  // UI_VIEWS_LAYOUT_BOX_LAYOUT_H_