[layoutng] Create correct constraint spaces for children

third_party/WebKit/Source/core/layout/ng/ng_constraint_space.h

 // Copyright 2016 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 NGConstraintSpace_h
 #define NGConstraintSpace_h
 
 #include "core/CoreExport.h"
 #include "core/layout/ng/ng_physical_constraint_space.h"
 #include "core/layout/ng/ng_writing_mode.h"
 #include "platform/heap/Handle.h"
 #include "wtf/text/WTFString.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class LayoutBox;
 class NGFragment;
 class NGLayoutOpportunityIterator;
 
 // The NGConstraintSpace represents a set of constraints and available space
 // which a layout algorithm may produce a NGFragment within. It is a view on
 // top of a NGPhysicalConstraintSpace and provides accessor methods in the
 // logical coordinate system defined by the writing mode given.
 class CORE_EXPORT NGConstraintSpace final
     : public GarbageCollected<NGConstraintSpace> {
  public:
   // Constructs a constraint space with a new backing NGPhysicalConstraintSpace.
+  // The size will be used for both for the physical constraint space's
+  // container size and this constraint space's Size().
   NGConstraintSpace(NGWritingMode, NGDirection, NGLogicalSize);
 
   // Constructs a constraint space based on an existing backing
-  // NGPhysicalConstraintSpace.
+  // NGPhysicalConstraintSpace. Sets this constraint space's size to the
+  // physical constraint space's container size, converted to logical
+  // coordinates.
+  // TODO(layout-ng): Do we need this constructor?
   NGConstraintSpace(NGWritingMode, NGDirection, NGPhysicalConstraintSpace*);
 
   // Constructs a constraint space with a different NGWritingMode and
-  // NGDirection.
+  // NGDirection that's otherwise identical.
   NGConstraintSpace(NGWritingMode, NGDirection, const NGConstraintSpace*);
 
   // Constructs a derived constraint space sharing the same backing
-  // NGPhysicalConstraintSpace, NGWritingMode and NGDirection.
+  // NGPhysicalConstraintSpace, NGWritingMode and NGDirection. Primarily for use
+  // by NGLayoutOpportunityIterator.
   NGConstraintSpace(const NGConstraintSpace& other,
                     NGLogicalOffset,
                     NGLogicalSize);
 
-  // Constructs a derived constraint space sharing the same backing
-  // NGPhysicalConstraintSpace, a different NGWritingMode and NGDirection.
+  // Constructs a derived constraint space that shares the exclusions of the
+  // input constraint space, but has a different container size, writing mode
+  // and direction. Sets the offset to zero. For use by layout algorithms
+  // to use as the basis to find layout opportunities for children.
   NGConstraintSpace(NGWritingMode,
                     NGDirection,
                     const NGConstraintSpace& other,
-                    NGLogicalOffset,
                     NGLogicalSize);
 
   // This should live on NGBox or another layout bridge and probably take a root
   // NGConstraintSpace or a NGPhysicalConstraintSpace.
   static NGConstraintSpace* CreateFromLayoutObject(const LayoutBox&);
 
   NGPhysicalConstraintSpace* PhysicalSpace() const { return physical_space_; }
 
   NGDirection Direction() const { return static_cast<NGDirection>(direction_); }
 
@@ skipping 63 matching lines @@
 };
 
 inline std::ostream& operator<<(std::ostream& stream,
                                 const NGConstraintSpace& value) {
   return stream << value.toString();
 }
 
 }  // namespace blink
 
 #endif  // NGConstraintSpace_h