mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Valentin Shergin
c4876d0313
Summary: The diff implements a new class called `AttributedStringBox` that represents an object storing a shared `AttributedString` *or* a shared pointer to some opaque platform-specific object that can be used as an attributed string. The class serves two main purposes: - Represent type-erased attributed string entity (which can be platform-specific or platform-independent); - Represent a container that can be copied with constant complexity. Why? Several reasons: - Sometimes it makes sense to keep an attributed string as a shared resource. This way we don't need to pay for expensive copying and we also implement a copy-on-write semantics on top of that if needed. - We need to extend a TextLayoutMeasure API to support measuring some platform-specific attributed string implementation to remove the necessity of converting a string back and forth between representations. That's especially important for TextInput because we will need to measure that very efficiently (and the source of measuring, in this case, is a platform attributed string). In other words, we need something to store inside TextInputState to measure and update very efficiently. The source of this data might be a native TextInput control or a data from React, to represent that kinda object we need this data structure (and interfaces that deal with it). Changelog: [Internal] Fabric-specific internal change. Reviewed By: sammy-SC Differential Revision: D18670793 fbshipit-source-id: bc0164f801f28642f7c6da340af12acf33b85d24
63 lines
1.7 KiB
C++
63 lines
1.7 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <memory>
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#include <react/attributedstring/AttributedString.h>
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namespace facebook {
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namespace react {
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/*
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* Represents an object storing a shared `AttributedString` or a shared pointer
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* to some opaque platform-specific object that can be used as an attributed
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* string. The class serves two main purposes:
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* - Represent type-erased attributed string entity (which can be
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* platform-specific or platform-independent);
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* - Represent a container that can be copied with constant complexity.
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*/
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class AttributedStringBox final {
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public:
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enum class Mode { Value, OpaquePointer };
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/*
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* Default constructor constructs an empty string.
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*/
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AttributedStringBox();
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/*
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* Custom explicit constructors.
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*/
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explicit AttributedStringBox(AttributedString const &value);
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explicit AttributedStringBox(std::shared_ptr<void> const &opaquePointer);
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/*
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* Movable, Copyable, Assignable.
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*/
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AttributedStringBox(AttributedStringBox const &other) = default;
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AttributedStringBox(AttributedStringBox &&other) noexcept = default;
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AttributedStringBox &operator=(AttributedStringBox const &other) = default;
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AttributedStringBox &operator=(AttributedStringBox &&other) = default;
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/*
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* Getters.
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*/
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Mode getMode() const;
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AttributedString const &getValue() const;
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std::shared_ptr<void> getOpaquePointer() const;
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private:
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Mode mode_;
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std::shared_ptr<AttributedString const> value_;
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std::shared_ptr<void> opaquePointer_;
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};
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} // namespace react
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} // namespace facebook
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