[LayoutNG] Abort a layout once the BFC offset is resolved.

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

Index: third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h b/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h
index f93787e18efd67a17a5773842dbf62c8e62f35b4..b34f0b86648a5761a2ca4aec098a0f3ca1418e5a 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.h
@@ -18,19 +18,35 @@ namespace blink {
 
 class NGConstraintSpace;
 class NGLayoutResult;
-struct NGInflowChildData;
-struct NGPreviousInflowPosition;
+
+// This struct is used for communicating to a child the position of the
+// previous inflow child.
+struct NGPreviousInflowPosition {
+  LayoutUnit bfc_block_offset;
+  LayoutUnit logical_block_offset;
+  NGMarginStrut margin_strut;
+};
+
+// This strut holds information for the current inflow child. The data is not
+// useful outside of handling this single inflow child.
+struct NGInflowChildData {
+  NGLogicalOffset bfc_offset_estimate;
+  NGMarginStrut margin_strut;
+  NGBoxStrut margins;
+};
 
 // Updates the fragment's BFC offset if it's not already set.
-void MaybeUpdateFragmentBfcOffset(const NGConstraintSpace&,
+bool MaybeUpdateFragmentBfcOffset(const NGConstraintSpace&,
                                   LayoutUnit bfc_block_offset,
                                   NGFragmentBuilder* builder);
 
 // Positions pending floats starting from {@origin_block_offset} and relative
 // to container's BFC offset.
-void PositionPendingFloats(LayoutUnit origin_block_offset,
-                           NGFragmentBuilder* container_builder,
-                           NGConstraintSpace* space);
+void PositionPendingFloats(
+    LayoutUnit origin_block_offset,
+    NGFragmentBuilder* container_builder,
+    Vector<RefPtr<NGUnpositionedFloat>>* unpositioned_floats,
+    NGConstraintSpace* space);
 
 // A class for general block layout (e.g. a <div> with no special style).
 // Lays out the children in sequence.
@@ -55,18 +71,21 @@ class CORE_EXPORT NGBlockLayoutAlgorithm
   // Creates a new constraint space for the current child.
   RefPtr<NGConstraintSpace> CreateConstraintSpaceForChild(
       const NGLayoutInputNode child,
-      const NGInflowChildData& child_data);
+      const NGInflowChildData& child_data,
+      const WTF::Optional<NGLogicalOffset> floats_bfc_offset = WTF::nullopt);
 
   // @return Estimated BFC offset for the "to be layout" child.
-  NGInflowChildData PrepareChildLayout(const NGPreviousInflowPosition&,
-                                       NGLayoutInputNode);
+  WTF::Optional<NGInflowChildData> PrepareChildLayout(
+      const NGPreviousInflowPosition&,
+      NGLayoutInputNode);
 
-  NGPreviousInflowPosition FinishChildLayout(
+  WTF::Optional<NGPreviousInflowPosition> FinishChildLayout(
       const NGConstraintSpace&,
       const NGPreviousInflowPosition& prev_data,
       const NGInflowChildData& child_data,
-      const NGLayoutInputNode child,
-      NGLayoutResult*);
+      NGLayoutInputNode child,
+      NGBreakToken* child_break_token,

[eae, 2017/07/10 23:27:49]

const?

[ikilpatrick, 2017/07/11 17:20:41]

Unfortunately not, we need to make the NGLayoutInputNodes const first.

We may want to consider explicitly have things mutable for the "Copy" functions,
etc so we have const correctness from the LayoutAlgorithm POV.

+      RefPtr<NGLayoutResult>);
 
   // Positions the fragment that establishes a new formatting context.
   //
@@ -87,14 +106,16 @@ class CORE_EXPORT NGBlockLayoutAlgorithm
   //    then it will be placed there and we collapse its margin.
   // 2) If #new-fc is too big then we need to clear its position and place it
   //    below #float ignoring its vertical margin.
-  NGLogicalOffset PositionNewFc(const NGLayoutInputNode& child,
-                                const NGPreviousInflowPosition&,
-                                const NGBoxFragment&,
-                                const NGInflowChildData& child_data,
-                                const NGConstraintSpace& child_space);
+  WTF::Optional<NGLogicalOffset> PositionNewFc(

[eae, 2017/07/10 23:27:49]

The API here is a bit confusing. Using the offset return value to both indicate
return code and offset isn't very clear, especially since it can return a
nullopt even if it did position floats.

Can we change this to return a status code or a bool instead and have the offset
be an output parameter?


ANewStatusEnum PositionNewFormattingContext(..., NGLogicalOffset*
resulting_offset);

bool CanPositionNewFormattingContext(..., NGLogicalOffset* resulting_offset);

[ikilpatrick, 2017/07/11 17:20:41]

done. Just did a bool atm.

+      const NGLayoutInputNode& child,
+      const NGPreviousInflowPosition&,
+      const NGLayoutResult&,
+      const NGInflowChildData& child_data,
+      const NGConstraintSpace& child_space);
 
   // Positions the fragment that knows its BFC offset.
-  NGLogicalOffset PositionWithBfcOffset(const NGLogicalOffset& bfc_offset);
+  WTF::Optional<NGLogicalOffset> PositionWithBfcOffset(
+      const NGLogicalOffset& bfc_offset);
 
   // Positions using the parent BFC offset.
   // Fragment doesn't know its offset but we can still calculate its BFC
@@ -134,6 +155,10 @@ class CORE_EXPORT NGBlockLayoutAlgorithm
   NGBoxStrut border_scrollbar_padding_;
   LayoutUnit content_size_;
   LayoutUnit max_inline_size_;
+
+  bool abort_when_bfc_resolved_;
+
+  Vector<RefPtr<NGUnpositionedFloat>> unpositioned_floats_;
 };
 
 }  // namespace blink