Don't reuse paragraph layouts prepared at another pixel density

Measured layouts are now carried over to clones with no new props or
children, including the ones configureYogaTree makes when the pixel
density changes. measureContent and findUsableLayout matched them only
by constraints or size, so the paragraph reused a layout prepared at the
old density and, with fixTextLayoutOnPixelDensityChange, never updated
its state to the new density. Only reuse layouts prepared at the current
pointScaleFactor.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: tomekzaw

packages/react-native/ReactCommon/react/renderer/components/text/ParagraphShadowNode.cpp

@@ -221,7 +221,8 @@ void ParagraphShadowNode::updateStateIfNeeded(const Content& content) {
           textLayoutManager_});
 }
 
-MeasuredPreparedTextLayout* ParagraphShadowNode::findUsableLayout() {
+MeasuredPreparedTextLayout* ParagraphShadowNode::findUsableLayout(
+    Float pointScaleFactor) {
   MeasuredPreparedTextLayout* ret = nullptr;
 
   if constexpr (TextLayoutManagerExtended::supportsPreparedTextLayout()) {
@@ -233,7 +234,8 @@ MeasuredPreparedTextLayout* ParagraphShadowNode::findUsableLayout() {
     // adjusted by a constraint (like min-size).
     auto expectedSize = rawContentSize();
     for (auto& prevLayout : measuredLayouts_) {
-      if (floatEquality(
+      if (prevLayout.pointScaleFactor == pointScaleFactor &&
+          floatEquality(
               prevLayout.measurement.size.width, expectedSize.width) &&
           floatEquality(
               prevLayout.measurement.size.height, expectedSize.height)) {
@@ -262,8 +264,11 @@ Size ParagraphShadowNode::measureContent(
     const LayoutContext& layoutContext,
     const LayoutConstraints& layoutConstraints) const {
   if constexpr (TextLayoutManagerExtended::supportsPreparedTextLayout()) {
+    // Layouts carried over from a previous revision may have been prepared
+    // at another pixel density, which they can't be reused for.
     for (const auto& layout : measuredLayouts_) {
-      if (layout.layoutConstraints == layoutConstraints) {
+      if (layout.layoutConstraints == layoutConstraints &&
+          layout.pointScaleFactor == layoutContext.pointScaleFactor) {
         return layout.measurement.size;
       }
     }
@@ -353,7 +358,7 @@ void ParagraphShadowNode::layout(LayoutContext layoutContext) {
   auto content =
       getContentWithMeasuredAttachments(layoutContext, layoutConstraints);
 
-  auto measuredLayout = findUsableLayout();
+  auto measuredLayout = findUsableLayout(layoutContext.pointScaleFactor);
 
   if constexpr (
       TextLayoutManagerExtended::supportsPreparedTextLayout() &&
@@ -370,7 +375,7 @@ void ParagraphShadowNode::layout(LayoutContext layoutContext) {
       // culled
       if (measuredLayout == nullptr) {
         measureContent(layoutContext, layoutConstraints);
-        measuredLayout = findUsableLayout();
+        measuredLayout = findUsableLayout(layoutContext.pointScaleFactor);
       }
       react_native_assert(measuredLayout);
       updateStateIfNeeded<ParagraphState>(content, *measuredLayout);

packages/react-native/ReactCommon/react/renderer/components/text/ParagraphShadowNode.h

@@ -117,9 +117,10 @@ class ParagraphShadowNode
 
   /**
    * Returns any previously prepared layout, generated for measurement, which
-   * may be used, given the currently assigned layout to the ShadowNode
+   * may be used, given the currently assigned layout to the ShadowNode and
+   * the current pixel density
    */
-  MeasuredPreparedTextLayout *findUsableLayout();
+  MeasuredPreparedTextLayout *findUsableLayout(Float pointScaleFactor);
 
   /**
    * Returns the final measure of the content frame, before layout rounding