[LayoutNG] Compute baseline from fragment tree

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

Index: third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h
index 5ea85591fb6a755835df5cda15452d82510f5f2c..056871f91a4fb485e9f17a64fc9ebf488ba2e34e 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.h
@@ -6,6 +6,7 @@
 #define NGFragmentBuilder_h
 
 #include "core/layout/ng/geometry/ng_static_position.h"
+#include "core/layout/ng/inline/ng_baseline.h"
 #include "core/layout/ng/inline/ng_physical_text_fragment.h"
 #include "core/layout/ng/ng_break_token.h"
 #include "core/layout/ng/ng_constraint_space.h"
@@ -31,6 +32,7 @@ class CORE_EXPORT NGFragmentBuilder final {
 
   using WeakBoxList = PersistentHeapLinkedHashSet<WeakMember<NGBlockNode>>;
 
+  NGWritingMode WritingMode() const { return writing_mode_; }
   NGFragmentBuilder& SetWritingMode(NGWritingMode);
   NGFragmentBuilder& SetDirection(TextDirection);
 
@@ -128,6 +130,8 @@ class CORE_EXPORT NGFragmentBuilder final {
     return children_;
   }
 
+  const Vector<NGLogicalOffset>& Offsets() const { return offsets_; }

[cbiesinger, 2017/07/12 15:48:44]

Add a brief comment that this is each child's offset? Or maybe rename to
ChildOffsets?

[kojii, 2017/07/12 18:21:53]

We have MutableOffsets() already and this is interface-compatible with
NGLineBoxFragmentBuilder. I'll add comment.

+
   bool DidBreak() const { return did_break_; }
 
   NGFragmentBuilder& SetBorderEdges(NGBorderEdges border_edges) {
@@ -135,6 +139,8 @@ class CORE_EXPORT NGFragmentBuilder final {
     return *this;
   }
 
+  void AddBaseline(NGBaselineAlgorithmType, FontBaseline, LayoutUnit);

[cbiesinger, 2017/07/12 15:48:44]

Could you add some brief documentation for how this is expected to work? Just
mention that for each baseline request in the constraint space, this function
should be called to provide the corresponding baseline, and the results are
undefined if it is called more than once for a given type/FontBaseline pair.

[kojii, 2017/07/12 18:21:53]

Thank you for pointing this out. I was caring comments for users of baselines
but forgot to think about algorithms. In a following patch.

+
  private:
   // An out-of-flow positioned-candidate is a temporary data structure used
   // within the NGFragmentBuilder.
@@ -187,6 +193,8 @@ class CORE_EXPORT NGFragmentBuilder final {
   WTF::Optional<NGLogicalOffset> bfc_offset_;
   NGMarginStrut end_margin_strut_;
 
+  Vector<NGBaseline> baselines_;
+
   NGBorderEdges border_edges_;
 };