third_party/WebKit/Source/core/layout/ng/ng_box_fragment.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_box_fragment.h"

#include "core/layout/LayoutBox.h"
#include "core/layout/ng/geometry/ng_logical_size.h"
#include "core/layout/ng/inline/ng_line_height_metrics.h"
#include "core/layout/ng/ng_constraint_space.h"
#include "core/layout/ng/ng_physical_box_fragment.h"

namespace blink {

NGLineHeightMetrics NGBoxFragment::BaselineMetrics(
    const NGBaselineRequest& request,
    const NGConstraintSpace& constraint_space) const {
  const auto& physical_fragment = ToNGPhysicalBoxFragment(physical_fragment_);

  LayoutBox* layout_box = ToLayoutBox(physical_fragment_.GetLayoutObject());
  bool is_parallel_writing_mode =
      IsHorizontalWritingMode(constraint_space.WritingMode()) ==
      layout_box->IsHorizontalWritingMode();

  if (is_parallel_writing_mode) {
    // Find the baseline from the computed results.
    if (const NGBaseline* baseline = physical_fragment.Baseline(request)) {
      LayoutUnit ascent = baseline->offset;
      LayoutUnit descent = BlockSize() - ascent;

      // For replaced elements, inline-block elements, and inline-table
      // elements, the height is the height of their margin box.
      // https://drafts.csswg.org/css2/visudet.html#line-height
      if (layout_box->IsAtomicInlineLevel()) {
        ascent += layout_box->MarginOver();
        descent += layout_box->MarginUnder();
      }

      return NGLineHeightMetrics(ascent, descent);
    }
  }

  // The baseline type was not found. This is either this box should synthesize
  // box-baseline without propagating from children, or caller forgot to add
  // baseline requests to constraint space when it called Layout().
  LayoutUnit block_size = BlockSize();

  // If atomic inline, use the margin box. See above.
  if (layout_box->IsAtomicInlineLevel()) {
    if (is_parallel_writing_mode)
      block_size += layout_box->MarginLogicalHeight();
    else
      block_size += layout_box->MarginLogicalWidth();
  }

  if (request.baseline_type == kAlphabeticBaseline)
    return NGLineHeightMetrics(block_size, LayoutUnit());
  return NGLineHeightMetrics(block_size - block_size / 2, block_size / 2);
}

}  // namespace blink