Add main axis alignment for BoxLayout.

ui/views/layout/box_layout.cc

Index: ui/views/layout/box_layout.cc
diff --git a/ui/views/layout/box_layout.cc b/ui/views/layout/box_layout.cc
index c11479678a998fe492103648b145b3e4911d81d2..8df124cf67906d335b8db57d53f5513f34eaeaac 100644
--- a/ui/views/layout/box_layout.cc
+++ b/ui/views/layout/box_layout.cc
@@ -19,7 +19,8 @@ BoxLayout::BoxLayout(BoxLayout::Orientation orientation,
                             inside_border_vertical_spacing,
                             inside_border_horizontal_spacing),
       between_child_spacing_(between_child_spacing),
-      spread_blank_space_(false) {
+      spread_blank_space_(false),
+      box_pack_(BOX_PACK_START) {
 }
 
 BoxLayout::~BoxLayout() {
@@ -29,38 +30,52 @@ void BoxLayout::Layout(View* host) {
   gfx::Rect child_area(host->GetLocalBounds());
   child_area.Inset(host->GetInsets());
   child_area.Inset(inside_border_insets_);
-  int x = child_area.x();
-  int y = child_area.y();
 
   int padding = 0;
-  if (spread_blank_space_) {
-    int total = 0;
+  if (box_pack_ != BOX_PACK_START || spread_blank_space_) {
+    int total_main_axis_size = 0;
     int visible = 0;

[sky, 2014/05/13 16:24:59]

visible -> num_visible or visible_count

[calamity, 2014/05/14 02:03:27]

Done.

     for (int i = 0; i < host->child_count(); ++i) {
       View* child = host->child_at(i);
       if (!child->visible())
         continue;
       if (orientation_ == kHorizontal) {
-        total += child->GetPreferredSize().width() + between_child_spacing_;
+        total_main_axis_size +=
+            child->GetPreferredSize().width() + between_child_spacing_;
       } else {
-        total += child->GetHeightForWidth(child_area.width()) +
-            between_child_spacing_;
+        total_main_axis_size += child->GetHeightForWidth(child_area.width()) +
+                                between_child_spacing_;
       }
       ++visible;
     }
 
     if (visible) {
-      total -= between_child_spacing_;
-      if (orientation_ == kHorizontal)
-        padding = (child_area.width() - total) / visible;
-      else
-        padding = (child_area.height() - total) / visible;
-
-      if (padding < 0)
-        padding = 0;
+      total_main_axis_size -= between_child_spacing_;
+      int free_space = MainAxisSize(child_area) - total_main_axis_size;
+      if (spread_blank_space_) {
+        padding = free_space / visible;

[sky, 2014/05/13 16:24:59]

This calculation isn't quite right.It has rounding areas. It may need to be
adjusted for the last view.

[calamity, 2014/05/14 02:03:27]

I don't quite understand what the problem here is?

Is it that the last view won't fully stretch to the end of the host?

e.g Host = 100 wide; 30 children. Each of them would be 3 wide, except the last
which should be 13?

Also, this code isn't changing functionally here. If there's a problem, could we
log it as a separate bug and fix it in another patch?

[sky, 2014/05/14 18:13:40]

Yes and sure.

[calamity, 2014/05/15 02:51:07]

Logged a bug at crbug.com/373571 .

+        if (padding < 0)
+          padding = 0;
+      } else {
+        int position = MainAxisPosition(child_area);
+        int size = MainAxisSize(child_area);
+        if (box_pack_ == BOX_PACK_CENTER) {
+          position += free_space / 2;
+          size = total_main_axis_size;
+        } else if (box_pack_ == BOX_PACK_END) {
+          position += free_space;
+          size = total_main_axis_size;
+        }
+        gfx::Rect new_child_area(child_area);
+        SetMainAxisPosition(&new_child_area, position);
+        SetMainAxisSize(&new_child_area, size);
+        child_area.Intersect(new_child_area);
+      }
     }
   }
 
+  int x = child_area.x();
+  int y = child_area.y();
   for (int i = 0; i < host->child_count(); ++i) {
     View* child = host->child_at(i);
     if (child->visible()) {
@@ -102,6 +117,28 @@ int BoxLayout::GetPreferredHeightForWidth(View* host, int width) {
   return GetPreferredSizeForChildWidth(host, child_width).height();
 }
 
+int BoxLayout::MainAxisSize(const gfx::Rect& child_area) {

[sky, 2014/05/13 16:24:59]

const on this and the next.

[calamity, 2014/05/14 02:03:27]

Done.

+  return orientation_ == kHorizontal ? child_area.width() : child_area.height();
+}
+
+int BoxLayout::MainAxisPosition(const gfx::Rect& child_area) {
+  return orientation_ == kHorizontal ? child_area.x() : child_area.y();
+}
+
+void BoxLayout::SetMainAxisSize(gfx::Rect* child_area, int size) {

[sky, 2014/05/13 16:24:59]

nit: style guide says out params should be last.

[calamity, 2014/05/14 02:03:27]

Done. This can be const too..

+  if (orientation_ == kHorizontal)
+    child_area->set_width(size);
+  else
+    child_area->set_height(size);
+}
+
+void BoxLayout::SetMainAxisPosition(gfx::Rect* child_area, int position) {
+  if (orientation_ == kHorizontal)
+    child_area->set_x(position);
+  else
+    child_area->set_y(position);
+}
+
 gfx::Size BoxLayout::GetPreferredSizeForChildWidth(View* host,
                                                    int child_area_width) {
   gfx::Rect child_area_bounds;