RNIsland UIA fragment root should report parents fragment root

change/react-native-windows-85407e5a-8b6f-41fe-b146-e73c385e9b34.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "RNIsland UIA fragment root should report parents fragment root",
+  "packageName": "react-native-windows",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

change/react-native-windows-db1edeae-cd39-4b02-9676-e41d36724426.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Fix crash running on server 2016",
+  "packageName": "react-native-windows",
+  "email": "30809111+acoates-ms@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

vnext/ExperimentalFeatures.props

@@ -1,6 +1,7 @@
 <Project>
   <PropertyGroup Condition="'$(SolutionName)'=='ReactWindows-Desktop'">
     <RnwNewArch>false</RnwNewArch>
+    <UseExperimentalWinUI3>true</UseExperimentalWinUI3>
   </PropertyGroup>
   <PropertyGroup>
     <ReactExperimentalFeaturesSet>true</ReactExperimentalFeaturesSet>

vnext/Microsoft.ReactNative/Fabric/Composition/CompositionRootAutomationProvider.cpp

@@ -27,6 +27,21 @@ HRESULT __stdcall CompositionRootAutomationProvider::GetRuntimeId(SAFEARRAY **pR
 
   *pRetVal = nullptr;
 
+  if (!m_island)
+    return E_FAIL;
+
+  auto id = reinterpret_cast<INT_PTR>(winrt::get_unknown(m_island));
+
+  *pRetVal = SafeArrayCreateVector(VT_I4, 0, 3);
+  if (*pRetVal == nullptr)
+    return E_OUTOFMEMORY;
+
+  auto rgiRuntimeId = static_cast<int*>((*pRetVal)->pvData);
+
+  rgiRuntimeId[0] = UiaAppendRuntimeId;
+  rgiRuntimeId[1] = LODWORD(id);
+  rgiRuntimeId[2] = HIDWORD(id);
+
   return S_OK;
 }
 
@@ -153,8 +168,18 @@ HRESULT __stdcall CompositionRootAutomationProvider::get_FragmentRoot(IRawElemen
   if (pRetVal == nullptr)
     return E_POINTER;
 
-  AddRef();
-  *pRetVal = this;
+  *pRetVal = nullptr;
+
+  if (m_island)
+  {
+    auto parentRoot = m_island.FragmentRootAutomationProvider();
+    auto spFragment = parentRoot.try_as<IRawElementProviderFragmentRoot>();
+    if (spFragment)
+    {
+      *pRetVal = spFragment.detach();
+      return S_OK;
+    }
+  }
 
   return S_OK;
 }
@@ -249,8 +274,6 @@ HRESULT __stdcall CompositionRootAutomationProvider::Navigate(
   if (pRetVal == nullptr)
     return E_POINTER;
 
-  // Fragment roots do not enable navigation to a parent or siblings; navigation among fragment roots is handled by the
-  // default window providers. Elements in fragments must navigate only to other elements within that fragment.
   if (direction == NavigateDirection_FirstChild || direction == NavigateDirection_LastChild) {
     if (auto rootView = rootComponentView()) {
       auto uiaProvider = rootView->EnsureUiaProvider();
@@ -260,6 +283,15 @@ HRESULT __stdcall CompositionRootAutomationProvider::Navigate(
         return S_OK;
       }
     }
+  } else if (direction == NavigateDirection_Parent) {
+    if (m_island) {
+      auto parent = m_island.ParentAutomationProvider();
+      auto spFragment = parent.try_as<IRawElementProviderFragment>();
+      if (spFragment) {
+        *pRetVal = spFragment.detach();
+        return S_OK;
+      }
+    }
   }
   *pRetVal = nullptr;
   return S_OK;

vnext/Microsoft.ReactNative/ReactHost/ReactInstanceWin.cpp

@@ -588,6 +588,24 @@ std::unique_ptr<facebook::jsi::PreparedScriptStore> CreatePreparedScriptStore()
 }
 
 #ifdef USE_FABRIC
+
+typedef HRESULT(__stdcall *SetThreadDescriptionFn)(HANDLE, PCWSTR);
+void SetJSThreadDescription() noexcept {
+  // Office still supports Server 2016 so we need to use Run Time Dynamic Linking and cannot just use:
+  // ::SetThreadDescription(GetCurrentThread(), L"React-Native JavaScript Thread");
+
+  auto moduleHandle = GetModuleHandleW(L"kernelbase.dll");
+  // The description is just for developer experience, so we can skip it if kernelbase isn't already loaded
+  if (!moduleHandle)
+    return;
+
+  auto proc = GetProcAddress(moduleHandle, "SetThreadDescription");
+  if (!proc)
+    return;
+
+  reinterpret_cast<SetThreadDescriptionFn>(proc)(GetCurrentThread(), L"React-Native JavaScript Thread");
+}
+
 void ReactInstanceWin::InitializeBridgeless() noexcept {
   InitUIQueue();
 
@@ -636,7 +654,7 @@ void ReactInstanceWin::InitializeBridgeless() noexcept {
                 Mso::Copy(m_whenDestroyed)));
 
             m_jsMessageThread.Load()->runOnQueueSync([&]() {
-              ::SetThreadDescription(GetCurrentThread(), L"React-Native JavaScript Thread");
+              SetJSThreadDescription();
               auto timerRegistry =
                   ::Microsoft::ReactNative::TimerRegistry::CreateTimerRegistry(m_reactContext->Properties());
               auto timerRegistryRaw = timerRegistry.get();