Implement collection of out-of-flow descendants

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

Index: third_party/WebKit/Source/core/layout/ng/ng_units.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_units.h b/third_party/WebKit/Source/core/layout/ng/ng_units.h
index 95151cc9e863cfc917fade2a82b04378dd7993f2..3f382a8f7c99be7ecc5b6379a028aa8b1b272582 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_units.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_units.h
@@ -57,6 +57,9 @@ struct NGLogicalOffset {
 
   // Converts a logical offset to a physical offset. See:
   // https://drafts.csswg.org/css-writing-modes-3/#logical-to-physical
+  // PhysicalOffset will be the physical top left point of the rectangle
+  // described by offset + inner_size. Setting inner_size to 0,0 will return
+  // the same point.
   // @param outer_size the size of the rect (typically a fragment).
   // @param inner_size the size of the inner rect (typically a child fragment).
   CORE_EXPORT NGPhysicalOffset
@@ -64,6 +67,7 @@ struct NGLogicalOffset {
                     TextDirection,
                     NGPhysicalSize outer_size,
                     NGPhysicalSize inner_size) const;
+
   bool operator==(const NGLogicalOffset& other) const;
 
   NGLogicalOffset operator+(const NGLogicalOffset& other) const;
@@ -92,6 +96,10 @@ struct NGPhysicalOffset {
 
   LayoutUnit left;
   LayoutUnit top;
+
+  NGPhysicalOffset operator+(const NGPhysicalOffset& other) const {

[ikilpatrick, 2016/12/02 17:47:06]

also define:
NGPhysicalOffset& operator+=(const NGPhysicalOffset other) const;

also probably move to .cc file to be consistent with NGLogicalOffset.

[atotic, 2016/12/02 19:55:16]

done. 

+= is not used yet, our current policy seems to be "define some operators, but
not other". Also, some are defined inline (NGBoxStrut), some not.

[ikilpatrick, 2016/12/02 21:06:13]

Thanks - this comes from:
https://google.github.io/styleguide/cppguide.html#Operator_Overloading
"If you define an operator, also define any related operators that make sense,
and make sure they are defined consistently."

+    return NGPhysicalOffset{this->left + other.left, this->top + other.top};
+  }
 };
 
 struct NGPhysicalSize {
@@ -267,6 +275,17 @@ struct NGEdge {
   LayoutUnit end;
 };
 
+// Represents rectangle's physical corner.

[ikilpatrick, 2016/12/02 17:47:06]

Maybe:

This struct is used to represent the static position of an out of flow
descendant.

(similar to NGMarginStruct, specifies which part of layout it's used for).

[atotic, 2016/12/02 19:55:16]

done

+struct CORE_EXPORT NGCorner {
+  enum Type { kTopLeft, kTopRight, kBottomLeft, kBottomRight };
+
+  Type type;  // Logical corner that corresponds to physical top left.

[ikilpatrick, 2016/12/02 17:47:06]

remove this comment?

[atotic, 2016/12/02 19:55:16]

Not done. I will not know what type is a year from now if this comment is
removed.

+  NGPhysicalOffset offset;
+
+  // Creates a corner with proper type wrt writing mode and direction.
+  static NGCorner Create(NGWritingMode, TextDirection, NGPhysicalOffset);
+};
+
 }  // namespace blink
 
 #endif  // NGUnits_h