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// 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 NGLineHeightMetrics_h
#define NGLineHeightMetrics_h
#include "third_party/blink/renderer/platform/fonts/font_baseline.h"
#include "third_party/blink/renderer/platform/layout_unit.h"
namespace blink {
class ComputedStyle;
class FontMetrics;
// 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 NGLineHeightMetrics {
NGLineHeightMetrics()
: ascent(LayoutUnit::Min()), descent(LayoutUnit::Min()) {}
NGLineHeightMetrics(LayoutUnit initial_ascent, LayoutUnit initial_descent)
: ascent(initial_ascent), descent(initial_descent) {}
// Compute from ComputedStyle, using the font metrics of the prikmary font.
// The leading is not included.
NGLineHeightMetrics(const ComputedStyle&);
NGLineHeightMetrics(const ComputedStyle&, FontBaseline);
// Compute from FontMetrics. The leading is not included.
NGLineHeightMetrics(const FontMetrics&, FontBaseline);
bool IsEmpty() const { return ascent == LayoutUnit::Min(); }
bool operator==(const NGLineHeightMetrics& other) const {
return ascent == other.ascent && descent == other.descent;
}
bool operator!=(const NGLineHeightMetrics& 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 NGLineHeightMetrics&);
void operator+=(const NGLineHeightMetrics&);
// 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;
LayoutUnit LineHeight() const { return ascent + descent; }
private:
void Initialize(const FontMetrics&, FontBaseline);
};
} // namespace blink
#endif // NGLineHeightMetrics_h
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