text: // 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.
  
  #ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FONT_HEIGHT_H_
  #define THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FONT_HEIGHT_H_
  
  #include "third_party/blink/renderer/platform/fonts/font_baseline.h"
  #include "third_party/blink/renderer/platform/geometry/layout_unit.h"
  
  namespace blink {
  
  // Represents line-progression metrics for line boxes and inline boxes.
  // Computed for inline boxes, then the metrics of inline boxes are united to
  // compute metrics for line boxes.
  // https://drafts.csswg.org/css2/visudet.html#line-height
  struct PLATFORM_EXPORT FontHeight {
    FontHeight() = default;
    FontHeight(LayoutUnit ascent, LayoutUnit descent)
        : ascent(ascent), descent(descent) {}
  
    // "Empty" is for when zero is a valid non-empty value.
    static FontHeight Empty() {
      return FontHeight(LayoutUnit::Min(), LayoutUnit::Min());
    }
    bool IsEmpty() const {
      return ascent == LayoutUnit::Min() && descent == LayoutUnit::Min();
    }
  
    LayoutUnit LineHeight() const { return ascent + descent; }
  
    bool operator==(const FontHeight& other) const {
      return ascent == other.ascent && descent == other.descent;
    }
    bool operator!=(const FontHeight& other) const { return !operator==(other); }
  
    // Add the leading. Half the leading is added to ascent and descent each.
    // https://drafts.csswg.org/css2/visudet.html#leading
    void AddLeading(LayoutUnit line_height);
  
    // Move the metrics by the specified amount, in line progression direction.
    void Move(LayoutUnit);
  
    // Unite a metrics for an inline box to a metrics for a line box.
    void Unite(const FontHeight&);
  
    void operator+=(const FontHeight&);
  
    // Ascent and descent of glyphs, or synthesized for replaced elements.
    // Then united to compute 'text-top' and 'text-bottom' of line boxes.
    LayoutUnit ascent;
    LayoutUnit descent;
  };
  
  PLATFORM_EXPORT std::ostream& operator<<(std::ostream&, const FontHeight&);
  
  }  // namespace blink
  
  #endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_FONT_HEIGHT_H_
  