Add Flex to views::BoxLayout.

ui/views/layout/box_layout.h

Index: ui/views/layout/box_layout.h
diff --git a/ui/views/layout/box_layout.h b/ui/views/layout/box_layout.h
index 54fa502eb569ef60643aaffd84962c3d326cfc7c..28124a4e5c14fdbf178e4a7e7d8f4d3abbce9934 100644
--- a/ui/views/layout/box_layout.h
+++ b/ui/views/layout/box_layout.h
@@ -5,6 +5,8 @@
 #ifndef UI_VIEWS_LAYOUT_BOX_LAYOUT_H_
 #define UI_VIEWS_LAYOUT_BOX_LAYOUT_H_
 
+#include <map>
+
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/gfx/insets.h"
@@ -38,11 +40,6 @@ class VIEWS_EXPORT BoxLayout : public LayoutManager {
     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.
   };
@@ -80,6 +77,24 @@ class VIEWS_EXPORT BoxLayout : public LayoutManager {
     inside_border_insets_ = insets;
   }
 
+  // Sets the flex weight for the view at |index|. Using the preferred size as
+  // the basis, free space along the main axis is distributed to views in the
+  // ratio of their flex weights. Similarly, if the views will overflow the
+  // parent, space is subtracted in these ratios.
+  //
+  // A flex of 0 means this view is not resized. Flex values must not be
+  // negative.
+  // Flex weights are set for the index and will not rearrange when the host's
+  // views do.
+  void SetFlexForViewAt(int index, int flex);

[sky, 2014/07/18 15:54:00]

Using indices like this is fragile and I suspect prone to unexpected conditions
(eg you set this for a view but a view and a new view gets inserted before the
view). I think this would make more sense to be View based.

[calamity, 2014/07/22 05:35:15]

Done.

+
+  // Clears the flex for the view at |index|, causing it to use the default
+  // flex.
+  void ClearFlexForViewAt(int index);
+
+  // Sets the flex for views to use when none is specified.
+  void SetDefaultFlex(int default_flex);
+
   // Overridden from views::LayoutManager:
   virtual void Layout(View* host) OVERRIDE;
   virtual gfx::Size GetPreferredSize(const View* host) const OVERRIDE;
@@ -87,6 +102,9 @@ class VIEWS_EXPORT BoxLayout : public LayoutManager {
                                          int width) const OVERRIDE;
 
  private:
+  // Returns the flex for the specified index.
+  int GetFlexForViewAt(int index);

[sky, 2014/07/18 15:54:00]

const

[calamity, 2014/07/22 05:35:14]

Done.

+
   // 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;
@@ -134,6 +152,12 @@ class VIEWS_EXPORT BoxLayout : public LayoutManager {
   // CROSS_AXIS_ALIGNMENT_STRETCH by default.
   CrossAxisAlignment cross_axis_alignment_;
 
+  // A map of view indexes to flex weights.
+  std::map<int, int> flex_map_;
+
+  // The flex weight for views if none is set. Defaults to 0.
+  int default_flex_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(BoxLayout);
 };