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..9af8e327d53645c39a2c2fda6198809e1e07a8ca 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.

[sashab, 2014/07/01 06:52:04]

Is this TODO still needed? This can be emulated with all child views having a
flex of 1.

[calamity, 2014/07/01 08:19:44]

This TODO outlines spreading the blank space to the spaces between the views
rather than among the views.

   };
@@ -80,6 +77,19 @@ class VIEWS_EXPORT BoxLayout : public LayoutManager {
     inside_border_insets_ = insets;
   }
 
+  void set_default_flex(int flex) { default_flex_ = flex; }

[sashab, 2014/07/01 06:52:04]

Is there a reason these methods use underscores and the other methods use camel
case?

[calamity, 2014/07/01 08:19:44]

Setting a property verbatim can be inlined and unix_cased. Anything else is
CamelCased and in the .cc.

+
+  // Sets the flex weight for the view at |index|. This uses the preferred main
+  // axis size as a basis and then distributes any free space along the main
+  // axis to the views in the ratio of the flex weights. If the views will
+  // overflow the parent in the main axis, this subtracts space from the views
+  // in the ratio of the flex weights.
+  void SetFlexForViewAt(int index, int flex);

[sashab, 2014/07/01 06:52:04]

Can flex be negative? Maybe add 'The flex cannot be negative' and add a
DCHECK().

I also think you can make this comment a bit clearer:
Sets the flex weight for the view at |index|. 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.

[calamity, 2014/07/01 08:19:44]

Done.

+
+  // Clears the flex for the view at |index|, causing it to use the default
+  // flex.
+  void ClearFlexForViewAt(int index);
+
   // Overridden from views::LayoutManager:
   virtual void Layout(View* host) OVERRIDE;
   virtual gfx::Size GetPreferredSize(const View* host) const OVERRIDE;
@@ -87,6 +97,9 @@ class VIEWS_EXPORT BoxLayout : public LayoutManager {
                                          int width) const OVERRIDE;
 
  private:
+  // Returns the flex for the specified index.

[sashab, 2014/07/01 06:52:04]

Nit: 'Returns the flex *for the view*...'

[calamity, 2014/07/01 08:19:44]

I think this is disingenuous as it implies the flex weight is linked to the
view. Also updated comment above to reflect that this is not the case.

+  int GetFlexForViewAt(int index);
+
   // 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 +147,12 @@ 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.

[sashab, 2014/07/01 06:52:04]

Add to this comment 'Defaults to 0.'

[calamity, 2014/07/01 08:19:44]

Done.

+  int default_flex_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(BoxLayout);
 };