CS of out-of-flow positioned objects should have is_new_fc == true

third_party/WebKit/Source/core/layout/ng/ng_constraint_space_builder.cc

 // 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.
 
 #include "core/layout/ng/ng_constraint_space_builder.h"
 
 #include "core/layout/ng/ng_length_utils.h"
 
 namespace blink {
 
 NGConstraintSpaceBuilder::NGConstraintSpaceBuilder(
     const NGConstraintSpace* parent_space)
     : available_size_(parent_space->AvailableSize()),
       percentage_resolution_size_(parent_space->PercentageResolutionSize()),
       initial_containing_block_size_(
           parent_space->InitialContainingBlockSize()),
       fragmentainer_space_available_(NGSizeIndefinite),
       parent_writing_mode_(parent_space->WritingMode()),
       is_fixed_size_inline_(false),
       is_fixed_size_block_(false),
       is_shrink_to_fit_(false),
       is_inline_direction_triggers_scrollbar_(false),
       is_block_direction_triggers_scrollbar_(false),
       fragmentation_type_(parent_space->BlockFragmentationType()),
-      is_new_fc_(parent_space->IsNewFormattingContext()),
+      is_new_fc_(false),
+      is_parent_new_fc_(parent_space->IsNewFormattingContext()),
       is_anonymous_(false),
       text_direction_(static_cast<unsigned>(parent_space->Direction())),
       bfc_offset_(parent_space->bfc_offset_),
       exclusions_(parent_space->Exclusions()) {}
 
 NGConstraintSpaceBuilder::NGConstraintSpaceBuilder(NGWritingMode writing_mode)
     : initial_containing_block_size_{NGSizeIndefinite, NGSizeIndefinite},
       fragmentainer_space_available_(NGSizeIndefinite),
       parent_writing_mode_(writing_mode),
       is_fixed_size_inline_(false),
       is_fixed_size_block_(false),
       is_shrink_to_fit_(false),
       is_inline_direction_triggers_scrollbar_(false),
       is_block_direction_triggers_scrollbar_(false),
       fragmentation_type_(kFragmentNone),
       is_new_fc_(false),
+      is_parent_new_fc_(false),
       is_anonymous_(false),
       text_direction_(static_cast<unsigned>(TextDirection::kLtr)),
       exclusions_(new NGExclusions()) {}
 
 NGConstraintSpaceBuilder& NGConstraintSpaceBuilder::SetAvailableSize(
     NGLogicalSize available_size) {
   available_size_ = available_size;
   return *this;
 }
 
@@ skipping 116 matching lines @@
       percentage_resolution_size.inline_size =
           initial_containing_block_size_.width;
     } else {
       percentage_resolution_size.inline_size =
           initial_containing_block_size_.height;
     }
   }
 
   // Reset things that do not pass the Formatting Context boundary.
   std::shared_ptr<NGExclusions> exclusions(
-      is_new_fc_ ? std::make_shared<NGExclusions>() : exclusions_);
-  NGLogicalOffset bfc_offset = is_new_fc_ ? NGLogicalOffset() : bfc_offset_;
+      is_parent_new_fc_ ? std::make_shared<NGExclusions>() : exclusions_);

[ikilpatrick, 2017/03/23 16:39:59]

yeah i'm not sure that I understand this, exclusions are only relevant to a
block formatting context, they don't affect layout of a child's BFC if it
establishes one... e.g. even if you have an inner float which is large, it wont
avoid other floats in the parent BFC; for example:

https://software.hixie.ch/utilities/js/live-dom-viewer/?%3C!DOCTYPE%20html%3E...

I think the issues is that the layout opportunity iterator shouldn't be using
the available inline size? I.e. it should be using the resolved inline size of
the fragment? 

[Gleb Lanbin, 2017/03/24 20:10:05]

updated based on the offline discussion.

   NGMarginStrut margin_strut = is_new_fc_ ? NGMarginStrut() : margin_strut_;
   WTF::Optional<LayoutUnit> clearance_offset =
       is_new_fc_ ? WTF::nullopt : clearance_offset_;
 
   if (is_in_parallel_flow) {
     return adoptRef(new NGConstraintSpace(
         static_cast<NGWritingMode>(out_writing_mode),
         static_cast<TextDirection>(text_direction_), available_size,
         percentage_resolution_size, initial_containing_block_size_,
         fragmentainer_space_available_, is_fixed_size_inline_,
         is_fixed_size_block_, is_shrink_to_fit_,
         is_inline_direction_triggers_scrollbar_,
         is_block_direction_triggers_scrollbar_,
         static_cast<NGFragmentationType>(fragmentation_type_), is_new_fc_,
-        is_anonymous_, margin_strut, bfc_offset, exclusions, clearance_offset));
+        is_anonymous_, margin_strut, bfc_offset_, exclusions,
+        clearance_offset));
   }
   return adoptRef(new NGConstraintSpace(
       out_writing_mode, static_cast<TextDirection>(text_direction_),
       available_size, percentage_resolution_size,
       initial_containing_block_size_, fragmentainer_space_available_,
       is_fixed_size_block_, is_fixed_size_inline_, is_shrink_to_fit_,
       is_block_direction_triggers_scrollbar_,
       is_inline_direction_triggers_scrollbar_,
       static_cast<NGFragmentationType>(fragmentation_type_), is_new_fc_,
-      is_anonymous_, margin_strut, bfc_offset, exclusions, clearance_offset));
+      is_anonymous_, margin_strut, bfc_offset_, exclusions, clearance_offset));
 }
 
 }  // namespace blink