third_party/WebKit/Source/core/layout/ng/ng_text_decoration_offset.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_text_decoration_offset.h"

#include "core/layout/line/RootInlineBox.h"
#include "core/layout/ng/inline/ng_baseline.h"
#include "core/layout/ng/inline/ng_physical_text_fragment.h"
#include "core/layout/ng/ng_physical_box_fragment.h"
#include "platform/fonts/FontMetrics.h"

namespace blink {

int NGTextDecorationOffset::ComputeUnderlineOffsetForUnder(
    float text_decoration_thickness,
    LineVerticalPositionType position_type) const {
  LayoutUnit offset = LayoutUnit::Max();

  if (decorating_box_) {
    // TODO(eae): Replace with actual baseline once available.
    NGBaselineRequest baseline_request = {
        NGBaselineAlgorithmType::kAtomicInline,
        FontBaseline::kIdeographicBaseline};

    const NGBaseline* baseline = decorating_box_->Baseline(baseline_request);
    if (baseline)
      offset = baseline->offset;
  }

  if (offset == LayoutUnit::Max()) {
    // TODO(layout-dev): How do we compute the baseline offset with a
    // decorating_box?
    offset = text_fragment_.Size().height;
  }

  // Compute offset to the farthest position of the decorating box.
  // TODO(layout-dev): This is quite incorrect.
  LayoutUnit logical_top = text_fragment_.Offset().top;
  LayoutUnit position = logical_top + offset;
  int offset_int = position.Floor();

  // Gaps are not needed for TextTop because it generally has internal
  // leadings.
  if (position_type == LineVerticalPositionType::TextTop)
    return offset_int;

  // TODO(layout-dev): Add or subtract one depending on side (IsLineOverSide).
  return offset_int + 1;
}

}  // namespace blink