Fabric: Introducing AttributedStringBox

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

ReactCommon/fabric/attributedstring/AttributedStringBox.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "AttributedStringBox.h"
+
+namespace facebook {
+namespace react {
+
+AttributedStringBox::AttributedStringBox()
+    : mode_(Mode::Value),
+      value_(std::make_shared<AttributedString const>(AttributedString{})),
+      opaquePointer_({}){};
+
+AttributedStringBox::AttributedStringBox(AttributedString const &value)
+    : mode_(Mode::Value),
+      value_(std::make_shared<AttributedString const>(value)),
+      opaquePointer_({}){};
+
+AttributedStringBox::AttributedStringBox(
+    std::shared_ptr<void> const &opaquePointer)
+    : mode_(Mode::OpaquePointer), value_({}), opaquePointer_(opaquePointer) {}
+
+AttributedStringBox::Mode AttributedStringBox::getMode() const {
+  return mode_;
+}
+
+AttributedString const &AttributedStringBox::getValue() const {
+  assert(mode_ == AttributedStringBox::Mode::Value);
+  assert(value_);
+  return *value_;
+}
+
+std::shared_ptr<void> AttributedStringBox::getOpaquePointer() const {
+  assert(mode_ == AttributedStringBox::Mode::OpaquePointer);
+  assert(opaquePointer_);
+  return opaquePointer_;
+}
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/attributedstring/AttributedStringBox.h

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <memory>
+
+#include <react/attributedstring/AttributedString.h>
+
+namespace facebook {
+namespace react {
+
+/*
+ * 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.
+ */
+class AttributedStringBox final {
+ public:
+  enum class Mode { Value, OpaquePointer };
+
+  /*
+   * Default constructor constructs an empty string.
+   */
+  AttributedStringBox();
+
+  /*
+   * Custom explicit constructors.
+   */
+  explicit AttributedStringBox(AttributedString const &value);
+  explicit AttributedStringBox(std::shared_ptr<void> const &opaquePointer);
+
+  /*
+   * Movable, Copyable, Assignable.
+   */
+  AttributedStringBox(AttributedStringBox const &other) = default;
+  AttributedStringBox(AttributedStringBox &&other) noexcept = default;
+  AttributedStringBox &operator=(AttributedStringBox const &other) = default;
+  AttributedStringBox &operator=(AttributedStringBox &&other) = default;
+
+  /*
+   * Getters.
+   */
+  Mode getMode() const;
+  AttributedString const &getValue() const;
+  std::shared_ptr<void> getOpaquePointer() const;
+
+ private:
+  Mode mode_;
+  std::shared_ptr<AttributedString const> value_;
+  std::shared_ptr<void> opaquePointer_;
+};
+
+} // namespace react
+} // namespace facebook

ReactCommon/fabric/components/text/paragraph/ParagraphShadowNode.cpp

@@ -7,6 +7,7 @@
 
 #include "ParagraphShadowNode.h"
 
+#include <react/attributedstring/AttributedStringBox.h>
 #include "ParagraphState.h"
 
 namespace facebook {
@@ -62,7 +63,9 @@ Size ParagraphShadowNode::measure(LayoutConstraints layoutConstraints) const {
   }
 
   return textLayoutManager_->measure(
-      attributedString, getProps()->paragraphAttributes, layoutConstraints);
+      AttributedStringBox{attributedString},
+      getProps()->paragraphAttributes,
+      layoutConstraints);
 }
 
 void ParagraphShadowNode::layout(LayoutContext layoutContext) {

ReactCommon/fabric/components/textinput/androidtextinput/AndroidTextInputShadowNode.cpp

@@ -8,6 +8,7 @@
 #include "AndroidTextInputShadowNode.h"
 
 #include <fb/fbjni.h>
+#include <react/attributedstring/AttributedStringBox.h>
 #include <react/attributedstring/TextAttributes.h>
 #include <react/components/text/BaseTextShadowNode.h>
 #include <react/core/LayoutConstraints.h>
@@ -111,7 +112,9 @@ Size AndroidTextInputShadowNode::measure(
   }
 
   return textLayoutManager_->measure(
-      attributedString, getProps()->paragraphAttributes, layoutConstraints);
+      AttributedStringBox{attributedString},
+      getProps()->paragraphAttributes,
+      layoutConstraints);
 }
 
 void AndroidTextInputShadowNode::layout(LayoutContext layoutContext) {

ReactCommon/fabric/textlayoutmanager/platform/android/TextLayoutManager.cpp

@@ -23,9 +23,11 @@ void *TextLayoutManager::getNativeTextLayoutManager() const {
 }
 
 Size TextLayoutManager::measure(
-    AttributedString attributedString,
+    AttributedStringBox attributedStringBox,
     ParagraphAttributes paragraphAttributes,
     LayoutConstraints layoutConstraints) const {
+  auto &attributedString = attributedStringBox.getValue();
+
   return measureCache_.get(
       MeasureCacheKey{attributedString, paragraphAttributes, layoutConstraints},
       [&](MeasureCacheKey const &key) {

ReactCommon/fabric/textlayoutmanager/platform/android/TextLayoutManager.h

@@ -10,6 +10,7 @@
 #include <memory>
 
 #include <react/attributedstring/AttributedString.h>
+#include <react/attributedstring/AttributedStringBox.h>
 #include <react/attributedstring/ParagraphAttributes.h>
 #include <react/core/LayoutConstraints.h>
 #include <react/utils/ContextContainer.h>
@@ -35,7 +36,7 @@ class TextLayoutManager {
    * Measures `attributedString` using native text rendering infrastructure.
    */
   Size measure(
-      AttributedString attributedString,
+      AttributedStringBox attributedStringBox,
       ParagraphAttributes paragraphAttributes,
       LayoutConstraints layoutConstraints) const;
 

ReactCommon/fabric/textlayoutmanager/platform/ios/TextLayoutManager.h

@@ -9,7 +9,7 @@
 
 #include <memory>
 
-#include <react/attributedstring/AttributedString.h>
+#include <react/attributedstring/AttributedStringBox.h>
 #include <react/attributedstring/ParagraphAttributes.h>
 #include <react/core/LayoutConstraints.h>
 #include <react/utils/ContextContainer.h>
@@ -34,7 +34,7 @@ class TextLayoutManager {
    * Measures `attributedString` using native text rendering infrastructure.
    */
   Size measure(
-      AttributedString attributedString,
+      AttributedStringBox attributedStringBox,
       ParagraphAttributes paragraphAttributes,
       LayoutConstraints layoutConstraints) const;
 

ReactCommon/fabric/textlayoutmanager/platform/ios/TextLayoutManager.mm

@@ -30,10 +30,12 @@ void *TextLayoutManager::getNativeTextLayoutManager() const
 }
 
 Size TextLayoutManager::measure(
-    AttributedString attributedString,
+    AttributedStringBox attributedStringBox,
     ParagraphAttributes paragraphAttributes,
     LayoutConstraints layoutConstraints) const
 {
+  auto &attributedString = attributedStringBox.getValue();
+
   return measureCache_.get(
       MeasureCacheKey{attributedString, paragraphAttributes, layoutConstraints}, [&](MeasureCacheKey const &key) {
         RCTTextLayoutManager *textLayoutManager = (__bridge RCTTextLayoutManager *)self_;