[Fabric] Implement maxFontSizeMultiplier in Text Input

change/react-native-windows-595c068c-640d-4645-a3e4-d6d23bf99c79.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "[Fabric] Implement maxFontSizeMultiplier in Text Input",
+  "packageName": "react-native-windows",
+  "email": "54227869+anupriya13@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

vnext/Microsoft.ReactNative/Fabric/Composition/TextInput/WindowsTextInputComponentView.cpp

@@ -1049,6 +1049,16 @@ void WindowsTextInputComponentView::updateProps(
     m_propBits |= TXTBIT_CHARFORMATCHANGE;
   }
 
+  // Uncomment below when this commit is merged in RNW:
+  // https://github.com/facebook/react-native/commit/97cf42f979e8303a3caeecb94cba1f5a82d1000c
+  // if (!facebook::react::floatEquality(
+  //        oldTextInputProps.textAttributes.maxFontSizeMultiplier,
+  //        newTextInputProps.textAttributes.maxFontSizeMultiplier)) {
+  //  m_propBitsMask |= TXTBIT_CHARFORMATCHANGE;
+  //  m_propBits |= TXTBIT_CHARFORMATCHANGE;
+  //  m_maxFontSizeMultiplier = newTextInputProps.textAttributes.maxFontSizeMultiplier;
+  //}
+
   if (oldTextInputProps.secureTextEntry != newTextInputProps.secureTextEntry) {
     m_propBitsMask |= TXTBIT_USEPASSWORD;
     if (newTextInputProps.secureTextEntry) {
@@ -1344,9 +1354,14 @@ void WindowsTextInputComponentView::UpdateCharFormat() noexcept {
 
   // set font size -- 15 to convert twips to pt
   const auto &props = windowsTextInputProps();
-  float fontSize = m_fontSizeMultiplier *
+  float fontSize =
       (std::isnan(props.textAttributes.fontSize) ? facebook::react::TextAttributes::defaultTextAttributes().fontSize
                                                  : props.textAttributes.fontSize);
+
+  // Apply maxFontSizeMultiplier if specified
+  fontSize *= (m_maxFontSizeMultiplier >= 1.0f) ? std::min(m_maxFontSizeMultiplier, m_fontSizeMultiplier)
+                                                : m_fontSizeMultiplier;
+
   // TODO get fontSize from props.textAttributes, or defaultTextAttributes, or fragment?
   cfNew.dwMask |= CFM_SIZE;
   cfNew.yHeight = static_cast<LONG>(fontSize * 15);

vnext/Microsoft.ReactNative/Fabric/Composition/TextInput/WindowsTextInputComponentView.h

@@ -128,6 +128,7 @@ struct WindowsTextInputComponentView
   unsigned int m_imgWidth{0}, m_imgHeight{0};
   std::shared_ptr<facebook::react::WindowsTextInputShadowNode::ConcreteState const> m_state;
   float m_fontSizeMultiplier{1.0};
+  float m_maxFontSizeMultiplier{0.0};
   int64_t m_mostRecentEventCount{0};
   int m_nativeEventCount{0};
   bool m_comingFromJS{false};