Fabric: Introducing BaseTextShadowNode::getAttributedString()

Summary:
`BaseTextShadowNode::getAttributedString()` was replaced with simular method `BaseTextShadowNode::buildAttributedString()` which does same work with following differences:
* Besides returning `AttributedString`, it retures an array of `Attachment`s elements of which points to `ShadowNode`s that form attachments;
* Now we use single `AttributedString` to construct result instead of concatenation objects recurvily walking the tree.

We will use the array of attachments later.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: sammy-SC

Differential Revision: D20268048

fbshipit-source-id: 371c548826bdfd5c4f4b18915d68977724885ce6

ReactCommon/fabric/components/text/basetext/BaseTextShadowNode.cpp

@@ -11,7 +11,6 @@
 #include <react/components/text/RawTextShadowNode.h>
 #include <react/components/text/TextProps.h>
 #include <react/components/text/TextShadowNode.h>
-#include <react/debug/DebugStringConvertibleItem.h>
 #include <react/mounting/ShadowView.h>
 
 namespace facebook {
@@ -26,51 +25,53 @@ inline ShadowView shadowViewFromShadowNode(ShadowNode const &shadowNode) {
   return shadowView;
 }
 
-AttributedString BaseTextShadowNode::getAttributedString(
-    TextAttributes const &textAttributes,
-    ShadowNode const &parentNode) {
-  auto attributedString = AttributedString{};
-
+void BaseTextShadowNode::buildAttributedString(
+    TextAttributes const &baseTextAttributes,
+    ShadowNode const &parentNode,
+    AttributedString &outAttributedString,
+    Attachments &outAttachments) {
   for (auto const &childNode : parentNode.getChildren()) {
     // RawShadowNode
     auto rawTextShadowNode =
-        std::dynamic_pointer_cast<const RawTextShadowNode>(childNode);
+        std::dynamic_pointer_cast<RawTextShadowNode const>(childNode);
     if (rawTextShadowNode) {
       auto fragment = AttributedString::Fragment{};
       fragment.string = rawTextShadowNode->getConcreteProps().text;
-      fragment.textAttributes = textAttributes;
+      fragment.textAttributes = baseTextAttributes;
 
       // Storing a retaining pointer to `ParagraphShadowNode` inside
       // `attributedString` causes a retain cycle (besides that fact that we
       // don't need it at all). Storing a `ShadowView` instance instead of
       // `ShadowNode` should properly fix this problem.
       fragment.parentShadowView = shadowViewFromShadowNode(parentNode);
-      attributedString.appendFragment(fragment);
+      outAttributedString.appendFragment(fragment);
       continue;
     }
 
     // TextShadowNode
     auto textShadowNode =
-        std::dynamic_pointer_cast<const TextShadowNode>(childNode);
+        std::dynamic_pointer_cast<TextShadowNode const>(childNode);
     if (textShadowNode) {
-      auto localTextAttributes = textAttributes;
+      auto localTextAttributes = baseTextAttributes;
       localTextAttributes.apply(
           textShadowNode->getConcreteProps().textAttributes);
-      attributedString.appendAttributedString(
-          textShadowNode->getAttributedString(
-              localTextAttributes, *textShadowNode));
+      buildAttributedString(
+          localTextAttributes,
+          *textShadowNode,
+          outAttributedString,
+          outAttachments);
       continue;
     }
 
-    // Any other kind of ShadowNode
+    // Any *other* kind of ShadowNode
     auto fragment = AttributedString::Fragment{};
     fragment.string = AttributedString::Fragment::AttachmentCharacter();
     fragment.parentShadowView = shadowViewFromShadowNode(*childNode);
-    fragment.textAttributes = textAttributes;
-    attributedString.appendFragment(fragment);
+    fragment.textAttributes = baseTextAttributes;
+    outAttributedString.appendFragment(fragment);
+    outAttachments.push_back(Attachment{
+        childNode.get(), outAttributedString.getFragments().size() - 1});
   }
-
-  return attributedString;
 }
 
 } // namespace react

ReactCommon/fabric/components/text/basetext/BaseTextShadowNode.h

@@ -20,15 +20,43 @@ namespace react {
 class BaseTextShadowNode {
  public:
   /*
-   * Returns a `AttributedString` which represents text content of the node.
+   * Represents additional information associated with some fragments which
+   * represent embedded into text component (such as an image or inline view).
+   */
+  class Attachment final {
+   public:
+    /*
+     * Unowning pointer to a `ShadowNode` that represents the attachment.
+     * Cannot be `null`.
+     */
+    ShadowNode const *shadowNode;
+
+    /*
+     * Index of the fragment in `AttributedString` that represents the
+     * the attachment.
+     */
+    size_t fragmentIndex;
+  };
+
+  /*
+   * A list of `Attachment`s.
+   * Performance-wise, the prevailing case is when there are no attachments
+   * at all, therefore we don't need an inline buffer (`small_vector`).
+   */
+  using Attachments = std::vector<Attachment>;
+
+  /*
+   * Builds an `AttributedString` which represents text content of the node.
    * This is static so that both Paragraph (which subclasses BaseText) and
    * TextInput (which does not) can use this.
    * TODO T53299884: decide if this should be moved out and made a static
    * function, or if TextInput should inherit from BaseTextShadowNode.
    */
-  static AttributedString getAttributedString(
+  static void buildAttributedString(
       TextAttributes const &baseTextAttributes,
-      ShadowNode const &parentNode);
+      ShadowNode const &parentNode,
+      AttributedString &outAttributedString,
+      Attachments &outAttachments);
 };
 
 } // namespace react

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

@@ -20,8 +20,12 @@ AttributedString ParagraphShadowNode::getAttributedString() const {
     auto textAttributes = TextAttributes::defaultTextAttributes();
     textAttributes.apply(getConcreteProps().textAttributes);
 
-    cachedAttributedString_ =
-        BaseTextShadowNode::getAttributedString(textAttributes, *this);
+    auto attributedString = AttributedString{};
+    auto attachments = Attachments{};
+    BaseTextShadowNode::buildAttributedString(
+        textAttributes, *this, attributedString, attachments);
+
+    cachedAttributedString_ = attributedString;
   }
 
   return cachedAttributedString_.value();

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

@@ -33,8 +33,11 @@ AttributedString AndroidTextInputShadowNode::getAttributedString() const {
   // Use BaseTextShadowNode to get attributed string from children
   auto childTextAttributes = TextAttributes::defaultTextAttributes();
   childTextAttributes.apply(getConcreteProps().textAttributes);
-  auto attributedString =
-      BaseTextShadowNode::getAttributedString(childTextAttributes, *this);
+
+  auto attributedString = AttributedString{};
+  auto attachments = BaseTextShadowNode::Attachments{};
+  BaseTextShadowNode::buildAttributedString(
+      childTextAttributes, *this, attributedString, attachments);
 
   // BaseTextShadowNode only gets children. We must detect and prepend text
   // value attributes manually.

ReactCommon/fabric/components/textinput/iostextinput/TextInputShadowNode.cpp

@@ -53,8 +53,10 @@ AttributedString TextInputShadowNode::getAttributedString() const {
   attributedString.appendFragment(
       AttributedString::Fragment{getConcreteProps().text, textAttributes});
 
-  attributedString.appendAttributedString(
-      BaseTextShadowNode::getAttributedString(textAttributes, *this));
+  auto attachments = Attachments{};
+  BaseTextShadowNode::buildAttributedString(
+      textAttributes, *this, attributedString, attachments);
+
   return attributedString;
 }