chromium/third_party/blink/renderer/platform/fonts/shaping/han_kerning.h

// Copyright 2023 The Chromium Authors
// 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_SHAPING_HAN_KERNING_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_SHAPING_HAN_KERNING_H_

#include "base/gtest_prod_util.h"
#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/blink/renderer/platform/text/han_kerning_char_type.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/forward.h"
#include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"

namespace blink {

class FontDescription;
class FontFeatures;
class LayoutLocale;
class SimpleFontData;

//
// This class implements the behavior necessary for the CSS `text-spacing-trim`
// property[1].
//
// In short, it's similar to kerning to be applied to Han-derived scripts such
// as Chinese or Japanese. In OpenType, this behavior is defined as the
// `chws`[2] feature.
//
// It's different from the regular kerning that the kerning pairs and amounts
// are computable. There are tools to add the features to existing fonts[3][4].
//
// This class complements the OpenType feature in that:
// 1. Handles the desired beahvior at the font boundaries. OpenType features
//    can't handle kerning at font boundaries by design.
// 2. Emulates the behavior when the font doesn't have the `chws` feature.
//
// [1]: https://drafts.csswg.org/css-text-4/#text-spacing-trim-property
// [2]:
// https://learn.microsoft.com/en-us/typography/opentype/spec/features_ae#tag-chws
// [3]: https://github.com/googlefonts/chws_tool
// [4]: https://github.com/kojiishi/east_asian_spacing
//
class PLATFORM_EXPORT HanKerning { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_SHAPING_HAN_KERNING_H_