Address some paragraph measure cache follow-up nits

Summary: Changing some T& to const T&, removing unnecessary shared_ptr.

Reviewed By: shergin

Differential Revision: D13845619

fbshipit-source-id: 2678f67f24445e3db105619a07534f5200e313fe

Author: JoshuaGross

ReactCommon/fabric/components/text/paragraph/ParagraphComponentDescriptor.h

@@ -34,7 +34,7 @@ class ParagraphComponentDescriptor final
     // Every single `ParagraphShadowNode` will have a reference to
     // a shared `EvictingCacheMap`, a simple LRU cache for Paragraph
     // measurements.
-    measureCache_ = std::make_shared<ParagraphMeasurementCache>();
+    measureCache_ = std::make_unique<ParagraphMeasurementCache>();
   }
 
   void adopt(UnsharedShadowNode shadowNode) const override {
@@ -50,7 +50,7 @@ class ParagraphComponentDescriptor final
 
     // `ParagraphShadowNode` uses this to cache the results of text rendering
     // measurements.
-    paragraphShadowNode->setMeasureCache(measureCache_);
+    paragraphShadowNode->setMeasureCache(measureCache_.get());
 
     // All `ParagraphShadowNode`s must have leaf Yoga nodes with properly
     // setup measure function.
@@ -59,7 +59,7 @@ class ParagraphComponentDescriptor final
 
  private:
   SharedTextLayoutManager textLayoutManager_;
-  SharedParagraphMeasurementCache measureCache_;
+  std::unique_ptr<const ParagraphMeasurementCache> measureCache_;
 };
 
 } // namespace react

ReactCommon/fabric/components/text/paragraph/ParagraphMeasurementCache.h

@@ -19,17 +19,11 @@ using ParagraphMeasurementCacheKey =
     std::tuple<AttributedString, ParagraphAttributes, LayoutConstraints>;
 using ParagraphMeasurementCacheValue = Size;
 
-using ParagraphMeasurementCacheHash = std::hash<ParagraphMeasurementCacheKey>;
-
-class ParagraphMeasurementCache;
-using SharedParagraphMeasurementCache =
-    std::shared_ptr<const ParagraphMeasurementCache>;
-
 class ParagraphMeasurementCache {
  public:
   ParagraphMeasurementCache() : cache_{256} {}
 
-  bool exists(ParagraphMeasurementCacheKey &key) const {
+  bool exists(const ParagraphMeasurementCacheKey &key) const {
     std::lock_guard<std::mutex> lock(mutex_);
     return cache_.exists(key);
   }
@@ -42,7 +36,7 @@ class ParagraphMeasurementCache {
 
   void set(
       const ParagraphMeasurementCacheKey &key,
-      ParagraphMeasurementCacheValue &value) const {
+      const ParagraphMeasurementCacheValue &value) const {
     std::lock_guard<std::mutex> lock(mutex_);
     cache_.set(key, value);
   }

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

@@ -33,7 +33,7 @@ void ParagraphShadowNode::setTextLayoutManager(
 }
 
 void ParagraphShadowNode::setMeasureCache(
-    SharedParagraphMeasurementCache cache) {
+    const ParagraphMeasurementCache *cache) {
   ensureUnsealed();
   measureCache_ = cache;
 }
@@ -63,16 +63,16 @@ Size ParagraphShadowNode::measure(LayoutConstraints layoutConstraints) const {
 
   // Cache results of this function so we don't need to call measure()
   // repeatedly
-  ParagraphMeasurementCacheKey hashValue =
+  ParagraphMeasurementCacheKey cacheKey =
       std::make_tuple(attributedString, attributes, layoutConstraints);
-  if (measureCache_->exists(hashValue)) {
-    return measureCache_->get(hashValue);
+  if (measureCache_->exists(cacheKey)) {
+    return measureCache_->get(cacheKey);
   }
 
-  Size measuredSize = textLayoutManager_->measure(
+  auto measuredSize = textLayoutManager_->measure(
       attributedString, getProps()->paragraphAttributes, layoutConstraints);
 
-  measureCache_->set(hashValue, measuredSize);
+  measureCache_->set(cacheKey, measuredSize);
 
   return measuredSize;
 }

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

@@ -53,8 +53,10 @@ class ParagraphShadowNode : public ConcreteViewShadowNode<
    * Associates a shared LRU cache with the node.
    * `ParagraphShadowNode` uses this to cache the results of
    * text rendering measurements.
+   * By design, the ParagraphComponentDescriptor outlives all
+   * shadow nodes, so it's safe for this to be a raw pointer.
    */
-  void setMeasureCache(SharedParagraphMeasurementCache cache);
+  void setMeasureCache(const ParagraphMeasurementCache *cache);
 
 #pragma mark - LayoutableShadowNode
 
@@ -69,7 +71,7 @@ class ParagraphShadowNode : public ConcreteViewShadowNode<
   void updateLocalDataIfNeeded();
 
   SharedTextLayoutManager textLayoutManager_;
-  SharedParagraphMeasurementCache measureCache_;
+  const ParagraphMeasurementCache *measureCache_;
 
   /*
    * Cached attributed string that represents the content of the subtree started