Top down version of algorithm to position margins and floats in LayoutNG

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.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 NGBlockLayoutAlgorithm_h
 #define NGBlockLayoutAlgorithm_h
 
 #include "core/CoreExport.h"
 #include "core/layout/ng/ng_block_node.h"
 #include "core/layout/ng/ng_layout_algorithm.h"
 #include "core/layout/ng/ng_units.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class ComputedStyle;
 class NGBlockBreakToken;
 class NGBreakToken;
 class NGColumnMapper;
 class NGConstraintSpace;
 class NGConstraintSpaceBuilder;
-class NGBoxFragment;
 class NGFragment;
 class NGFragmentBuilder;
 class NGPhysicalFragment;
 
 // A class for general block layout (e.g. a <div> with no special style).
 // Lays out the children in sequence.
 class CORE_EXPORT NGBlockLayoutAlgorithm : public NGLayoutAlgorithm {
  public:
   // Default constructor.
   // @param layout_object The layout object associated with this block.
@@ skipping 58 matching lines @@
   // Get the amount of block space left in the current fragmentainer for the
   // child that is about to be laid out.
   LayoutUnit SpaceAvailableForCurrentChild() const;
 
   LayoutUnit BorderEdgeForCurrentChild() const {
     // TODO(mstensho): Need to take care of margin collapsing somehow. We
     // should at least attempt to estimate what the top margin is going to be.
     return content_size_;
   }
 
-  // Computes collapsed margins for 2 adjoining blocks and updates the resultant
-  // fragment's MarginStrut if needed.
-  // See https://www.w3.org/TR/CSS2/box.html#collapsing-margins
-  //
-  // @param child_margins Margins information for the current child.
-  // @param fragment Current child's fragment.
-  // @return NGBoxStrut with margins block start/end.
-  NGBoxStrut CollapseMargins(const NGBoxStrut& child_margins,
-                             const NGBoxFragment& fragment);
-
-  // Calculates position of the in-flow block-level fragment that needs to be
-  // positioned relative to the current fragment that is being built.
-  //
-  // @param fragment Fragment that needs to be placed.
-  // @param child_margins Margins information for the current child fragment.
-  // @return Position of the fragment in the parent's constraint space.
-  NGLogicalOffset PositionFragment(const NGFragment& fragment,
-                                   const NGBoxStrut& child_margins);
-
-  // Calculates position of the float fragment that needs to be
-  // positioned relative to the current fragment that is being built.
-  //
-  // @param fragment Fragment that needs to be placed.
-  // @param child_margins Margins information for the current child fragment.
-  // @return Position of the fragment in the parent's constraint space.
-  NGLogicalOffset PositionFloatFragment(const NGFragment& fragment,
-                                        const NGBoxStrut& child_margins);
-
-  // Updates block-{start|end} of the currently constructed fragment.
-  //
-  // This method is supposed to be called on every child but it only updates
-  // the block-start once (on the first non-zero height child fragment) and
-  // keeps updating block-end (on every non-zero height child).
-  void UpdateMarginStrut(const NGDeprecatedMarginStrut& from);
+  // Calculates relative position for the fragment that knows its offset.
+  NGLogicalOffset PositionFragmentWithKnownBfcOffset(
+      const NGLogicalOffset& offset);
 
   NGLogicalOffset GetChildSpaceOffset() const {
     return NGLogicalOffset(border_and_padding_.inline_start, content_size_);
   }
 
   // Read-only Getters.
   const ComputedStyle& CurrentChildStyle() const {
     DCHECK(current_child_);
     return *current_child_->Style();
   }
@@ skipping 23 matching lines @@
 
   // Mapper from the fragmented flow coordinate space coordinates to visual
   // coordinates. Only set on fragmentation context roots, such as multicol
   // containers. Keeps track of the current fragmentainer.
   Member<NGColumnMapper> fragmentainer_mapper_;
 
   NGBoxStrut border_and_padding_;
   LayoutUnit content_size_;
   LayoutUnit max_inline_size_;
   // MarginStrut for the previous child.
-  NGDeprecatedMarginStrut prev_child_margin_strut_;
-  // Whether the block-start was set for the currently built
-  // fragment's margin strut.
-  bool is_fragment_margin_strut_block_start_updated_ : 1;
+  NGMarginStrut curr_margin_strut_;
+  NGLogicalOffset bfc_offset_;
+  NGLogicalOffset curr_bfc_offset_;
   NGBoxStrut curr_child_margins_;
 };
 
 }  // namespace blink
 
 #endif  // NGBlockLayoutAlgorithm_h