[ash-md] Adds support for Z-order iteration in views::View

ui/views/view.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_VIEW_H_
 #define UI_VIEWS_VIEW_H_
 
 #include <stddef.h>
 
 #include <algorithm>
@@ skipping 172 matching lines @@
   // the view at the end.
   void ReorderChildView(View* view, int index);
 
   // Removes |view| from this view. The view's parent will change to NULL.
   void RemoveChildView(View* view);
 
   // Removes all the children from this view. If |delete_children| is true,
   // the views are deleted, unless marked as not parent owned.
   void RemoveAllChildViews(bool delete_children);
 
   int child_count() const { return static_cast<int>(children_.size()); }

[sky, 2016/12/13 23:40:56]

Please add a comment here about GetChildrenOrderedByVisualOrder().

[varkha, 2016/12/19 20:35:44]

Done.

   bool has_children() const { return !children_.empty(); }
 
   // Returns the child view at |index|.
   const View* child_at(int index) const {
     DCHECK_GE(index, 0);
     DCHECK_LT(index, child_count());
     return children_[index];
   }
   View* child_at(int index) {
     return const_cast<View*>(const_cast<const View*>(this)->child_at(index));
@@ skipping 96 matching lines @@
   virtual bool IsDrawn() const;
 
   // Set whether this view is enabled. A disabled view does not receive keyboard
   // or mouse inputs. If |enabled| differs from the current value, SchedulePaint
   // is invoked. Also, clears focus if the focused view is disabled.
   void SetEnabled(bool enabled);
 
   // Returns whether the view is enabled.
   bool enabled() const { return enabled_; }
 
+  // Get a container of |children_| arranged according to the stacking order.

[sky, 2016/12/13 23:40:56]

How about:
Returns the child views ordered in reverse z-order. That is, views later in the
returned vector have a higher z-order (are painted later) than those early in
the vector. The returned vector has exactly the same number of Views as
children(). The default implementation returns children(), subclass if the paint
order should differ from that of children().

I'm also wondering if it should be named GetChildrenOrderedByZOrder()? But I'm
ok with what you have.

Can this be protected?

[varkha, 2016/12/14 17:51:38]

I will look into the rest of the comments but making it protected would require
friending ViewTargeterDelegate::TargetForRect, no?

[varkha, 2016/12/19 20:35:44]

Done (edited the comment).

+  // This defaults to returning |children_| but can be overridden to implement
+  // a different stacking order. This order is taken into account by painting
+  // and targeting implementations.
+  virtual View::Views GetChildrenOrderedByVisualOrder();
+
   // Transformations -----------------------------------------------------------
 
   // Methods for setting transformations for a view (e.g. rotation, scaling).
 
   gfx::Transform GetTransform() const;
 
   // Clipping is done relative to the view's local bounds.
   void set_clip_path(const gfx::Path& path) { clip_path_ = path; }
 
   // Sets the transform to the supplied transform.
@@ skipping 1263 matching lines @@
   // Observers -------------------------------------------------------------
 
   base::ObserverList<ViewObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(View);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_VIEW_H_