chromium/third_party/blink/renderer/platform/text/writing_mode_utils.h

// Copyright 2017 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_TEXT_WRITING_MODE_UTILS_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_TEXT_WRITING_MODE_UTILS_H_

#include "third_party/blink/renderer/platform/text/writing_direction_mode.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"

namespace blink {

// Templates to map values between logical orientations and physical
// orientations. See https://www.w3.org/TR/css-writing-modes-3/ and
// https://www.w3.org/TR/css-logical-1/ for definitions of logical orientations.

// This file provides two types of templates:
//
// - Simple value mappers (PhysicalToLogical and LogicalToPhysical): they take
//   4 input values in physical or logical orientations, and provide accessors
//   to get values in logical or physical orientations. As the inputs may be
//   evaluated even if not used (in case that the compiler is unable to remove
//   unused evaluations, e.g. containing non-inlined function calls), for
//   performance-senstive code, the evaluation of the inputs should be simple
//   and/or be fully inlined.
//
// - Value mappers based on getter/setter methods (PhysicalToLogicalGetter,
//   LogicalToPhysicalGetter, PhysicalToLogicalSetter and
//   LogicalToPhysicalSetter): they take 4 method pointers as inputs pointing to
//   methods accessing values in physical or logical orientations, and provide
//   accessors to get or set values in logical or physical orientations. They
//   are suitable for mapping of setters, or getters implemented with non-
//   inlined functions. Evaluation of the input values are delayed when they are
//   actually needed.
//
// See WritingModeUtilsTest.cpp, LayoutBoxModelObject.h and ComputedStyle.h for
// examples.

template <typename Value>
class PhysicalToLogical { … };

template <typename Value>
class LogicalToPhysical { … };

template <typename Value>
class LogicalToLogical { … };

template <typename Value, typename Object>
class LogicalToPhysicalGetter { … };

template <typename Value, typename Object>
class PhysicalToLogicalGetter { … };

template <typename Value, typename Object>
class LogicalToPhysicalSetter { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_TEXT_WRITING_MODE_UTILS_H_