enable/disable on focus changed; remove unnecessary bool

src/cascadia/PublicTerminalCore/HwndTerminal.cpp

@@ -320,8 +320,7 @@ IRawElementProviderSimple* HwndTerminal::_GetUiaProvider() noexcept
 {
     // If TermControlUiaProvider throws during construction,
     // we don't want to try constructing an instance again and again.
-    // _uiaProviderInitialized helps us prevent this.
-    if (!_uiaProviderInitialized)
+    if (!_uiaProvider)
     {
         try
         {
@@ -330,7 +329,6 @@ IRawElementProviderSimple* HwndTerminal::_GetUiaProvider() noexcept
             _uiaEngine = std::make_unique<::Microsoft::Console::Render::UiaEngine>(_uiaProvider.Get());
             LOG_IF_FAILED(_uiaEngine->Enable());
             _renderer->AddRenderEngine(_uiaEngine.get());
-            _uiaProviderInitialized = true;
         }
         catch (...)
         {
@@ -724,7 +722,7 @@ try
     {
         modifiers |= ControlKeyStates::EnhancedKey;
     }
-    if (vkey && keyDown && _uiaProviderInitialized)
+    if (vkey && keyDown && _uiaProvider)
     {
         _uiaProvider->RecordKeyEvent(vkey);
     }
@@ -836,12 +834,20 @@ void __stdcall TerminalSetFocus(void* terminal)
 {
     auto publicTerminal = static_cast<HwndTerminal*>(terminal);
     publicTerminal->_focused = true;
+    if (auto uiaEngine = publicTerminal->_uiaEngine.get())
+    {
+        LOG_IF_FAILED(uiaEngine->Enable());
+    }
 }
 
 void __stdcall TerminalKillFocus(void* terminal)
 {
     auto publicTerminal = static_cast<HwndTerminal*>(terminal);
     publicTerminal->_focused = false;
+    if (auto uiaEngine = publicTerminal->_uiaEngine.get())
+    {
+        LOG_IF_FAILED(uiaEngine->Disable());
+    }
 }
 
 // Routine Description:

src/cascadia/PublicTerminalCore/HwndTerminal.hpp

@@ -83,7 +83,6 @@ private:
     std::unique_ptr<::Microsoft::Console::Render::UiaEngine> _uiaEngine;
 
     bool _focused{ false };
-    bool _uiaProviderInitialized{ false };
 
     std::chrono::milliseconds _multiClickTime;
     unsigned int _multiClickCounter{};

src/cascadia/PublicTerminalCore/HwndTerminalAutomationPeer.hpp

@@ -6,17 +6,10 @@ Module Name:
 - HwndTerminalAutomationPeer.hpp
 
 Abstract:
-- This module provides UI Automation access to the TermControl
+- This module provides UI Automation access to the HwndTerminal
   to support both automation tests and accessibility (screen
-  reading) applications. This mainly interacts with ScreenInfoUiaProvider
-  to allow for shared code between ConHost and Windows Terminal
-  accessibility providers.
-- Based on the Custom Automation Peers guide on msdn
-  (https://docs.microsoft.com/en-us/windows/uwp/design/accessibility/custom-automation-peers)
-- Wraps the UIAutomationCore ITextProvider
-  (https://docs.microsoft.com/en-us/windows/win32/api/uiautomationcore/nn-uiautomationcore-itextprovider)
-  with a XAML ITextProvider
-  (https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.automation.provider.itextprovider)
+  reading) applications. This mainly interacts with TermControlUiaProvider
+  to allow for shared code with Windows Terminal accessibility providers.
 
 Author(s):
 - Carlos Zamora   (CaZamor)    2022