Move NG floats utility methods to the separate file

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

+// Copyright 2017 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_floats_utils.h"
+
+#include "core/layout/ng/ng_box_fragment.h"
+
+namespace blink {
+namespace {
+
+// Adjusts the provided offset to the top edge alignment rule.
+// Top edge alignment rule: the outer top of a floating box may not be higher
+// than the outer top of any block or floated box generated by an element
+// earlier in the source document.
+NGLogicalOffset AdjustToTopEdgeAlignmentRule(const NGConstraintSpace& space,
+                                             const NGLogicalOffset& offset) {
+  NGLogicalOffset adjusted_offset = offset;
+  LayoutUnit& adjusted_block_offset = adjusted_offset.block_offset;
+  if (space.Exclusions()->last_left_float)
+    adjusted_block_offset =
+        std::max(adjusted_block_offset,
+                 space.Exclusions()->last_left_float->rect.BlockStartOffset());
+  if (space.Exclusions()->last_right_float)
+    adjusted_block_offset =
+        std::max(adjusted_block_offset,
+                 space.Exclusions()->last_right_float->rect.BlockStartOffset());
+  return adjusted_offset;
+}
+
+// Finds a layout opportunity for the fragment.
+// It iterates over all layout opportunities in the constraint space and returns
+// the first layout opportunity that is wider than the fragment or returns the
+// last one which is always the widest.
+//
+// @param space Constraint space that is used to find layout opportunity for
+//              the fragment.
+// @param fragment Fragment that needs to be placed.
+// @param origin_point {@code space}'s offset relative to the space that
+//                     establishes a new formatting context that we're currently
+//                     in and where all our exclusions reside.
+// @param margins Margins of the fragment.
+// @return Layout opportunity for the fragment.
+const NGLayoutOpportunity FindLayoutOpportunityForFragment(
+    const NGConstraintSpace* space,
+    const NGFragment& fragment,
+    const NGLogicalOffset& origin_point,
+    const NGBoxStrut& margins) {
+  NGLogicalOffset adjusted_origin_point =
+      AdjustToTopEdgeAlignmentRule(*space, origin_point);
+
+  NGLayoutOpportunityIterator opportunity_iter(space, adjusted_origin_point);
+  NGLayoutOpportunity opportunity;
+  NGLayoutOpportunity opportunity_candidate = opportunity_iter.Next();
+
+  while (!opportunity_candidate.IsEmpty()) {
+    opportunity = opportunity_candidate;
+    // Checking opportunity's block size is not necessary as a float cannot be
+    // positioned on top of another float inside of the same constraint space.
+    auto fragment_inline_size = fragment.InlineSize() + margins.InlineSum();
+    if (opportunity.size.inline_size >= fragment_inline_size)
+      break;
+
+    opportunity_candidate = opportunity_iter.Next();
+  }
+  return opportunity;
+}
+
+// Calculates the logical offset for opportunity.
+NGLogicalOffset CalculateLogicalOffsetForOpportunity(
+    const NGLayoutOpportunity& opportunity,
+    const LayoutUnit float_offset,
+    const NGLogicalOffset& from_offset,
+    NGFloatingObject* floating_object) {
+  DCHECK(floating_object);
+  auto margins = floating_object->margins;
+  // Adjust to child's margin.
+  LayoutUnit inline_offset = margins.inline_start;
+  LayoutUnit block_offset = margins.block_start;
+
+  // Offset from the opportunity's block/inline start.
+  inline_offset += opportunity.offset.inline_offset;
+  block_offset += opportunity.offset.block_offset;
+
+  // Adjust to float: right offset if needed.
+  inline_offset += float_offset;
+
+  block_offset -= from_offset.block_offset;
+  inline_offset -= from_offset.inline_offset;
+
+  return NGLogicalOffset(inline_offset, block_offset);
+}
+
+// Creates an exclusion from the fragment that will be placed in the provided
+// layout opportunity.
+NGExclusion CreateExclusion(const NGFragment& fragment,
+                            const NGLayoutOpportunity& opportunity,
+                            const LayoutUnit float_offset,
+                            const NGBoxStrut& margins,
+                            NGExclusion::Type exclusion_type) {
+  NGExclusion exclusion;
+  exclusion.type = exclusion_type;
+  NGLogicalRect& rect = exclusion.rect;
+  rect.offset = opportunity.offset;
+  rect.offset.inline_offset += float_offset;
+
+  rect.size.inline_size = fragment.InlineSize() + margins.InlineSum();
+  rect.size.block_size = fragment.BlockSize() + margins.BlockSum();
+  return exclusion;
+}
+
+// Updates the Floating Object's left offset from the provided parent_space
+// and {@code floating_object}'s space and margins.
+void UpdateFloatingObjectLeftOffset(const NGConstraintSpace& new_parent_space,
+                                    const NGLogicalOffset& float_logical_offset,
+                                    NGFloatingObject* floating_object) {
+  DCHECK(floating_object);
+  // TODO(glebl): We should use physical offset here.
+  floating_object->left_offset =
+      floating_object->original_parent_space->BfcOffset().inline_offset -
+      new_parent_space.BfcOffset().inline_offset +
+      float_logical_offset.inline_offset;
+}
+}  // namespace
+
+// Calculates the relative position from {@code from_offset} of the
+// floating object that is requested to be positioned from {@code origin_point}.
+NGLogicalOffset PositionFloat(const NGLogicalOffset& origin_point,
+                              const NGLogicalOffset& from_offset,
+                              NGFloatingObject* floating_object,
+                              NGConstraintSpace* new_parent_space) {
+  DCHECK(floating_object);
+  const auto* float_space = floating_object->space.get();
+  DCHECK(floating_object->fragment) << "Fragment cannot be null here";
+
+  // TODO(ikilpatrick): The writing mode switching here looks wrong.
+  NGBoxFragment float_fragment(
+      float_space->WritingMode(),
+      toNGPhysicalBoxFragment(floating_object->fragment.get()));
+
+  // Find a layout opportunity that will fit our float.
+  const NGLayoutOpportunity opportunity = FindLayoutOpportunityForFragment(
+      float_space, float_fragment, origin_point, floating_object->margins);
+  DCHECK(!opportunity.IsEmpty()) << "Opportunity is empty but it shouldn't be";
+
+  // Calculate the float offset if needed.
+  LayoutUnit float_offset;
+  if (floating_object->exclusion_type == NGExclusion::kFloatRight) {
+    LayoutUnit float_margin_box_inline_size =
+        float_fragment.InlineSize() + floating_object->margins.InlineSum();
+    float_offset = opportunity.size.inline_size - float_margin_box_inline_size;
+  }
+
+  // Add the float as an exclusion.
+  const NGExclusion exclusion = CreateExclusion(
+      float_fragment, opportunity, float_offset, floating_object->margins,
+      floating_object->exclusion_type);
+  new_parent_space->AddExclusion(exclusion);
+
+  NGLogicalOffset logical_offset = CalculateLogicalOffsetForOpportunity(
+      opportunity, float_offset, from_offset, floating_object);
+  UpdateFloatingObjectLeftOffset(*new_parent_space, logical_offset,
+                                 floating_object);
+  return logical_offset;
+}
+}  // namespace blink