Fire UIA Events for Output and Cursor Movement (#4826)

## Summary of the Pull Request
This notifies automation clients (i.e.: NVDA, narrator, etc...) of new output being rendered to the screen.

## References
Close #2447 - Signaling for new output and cursor
Close #3791 - fixed by signaling cursor changes

## Detailed Description of the Pull Request / Additional comments
- Added tracing for UiaRenderer. This makes it easier to debug issues with notifying an automation client.
- Fire TextChanged automation events when new content is output to the screen.

## Validation Steps Performed
Verified with NVDA [1]

## Narrator
Narrator works _better_, but is unable to detect new output consistently. There is no harm for narrator when this change goes in.

[1] https://github.com/microsoft/terminal/issues/2447#issuecomment-595879890

src/cascadia/TerminalControl/TermControlAutomationPeer.cpp

@@ -9,6 +9,7 @@
 #include "TermControlAutomationPeer.g.cpp"
 
 #include "XamlUiaTextRange.h"
+#include "..\types\UiaTracing.h"
 
 using namespace Microsoft::Console::Types;
 using namespace winrt::Windows::UI::Xaml::Automation::Peers;
@@ -44,6 +45,7 @@ namespace winrt::Microsoft::Terminal::TerminalControl::implementation
     // - <none>
     void TermControlAutomationPeer::SignalSelectionChanged()
     {
+        UiaTracing::Signal::SelectionChanged();
         Dispatcher().RunAsync(Windows::UI::Core::CoreDispatcherPriority::Normal, [&]() {
             // The event that is raised when the text selection is modified.
             RaiseAutomationEvent(AutomationEvents::TextPatternOnTextSelectionChanged);
@@ -58,6 +60,7 @@ namespace winrt::Microsoft::Terminal::TerminalControl::implementation
     // - <none>
     void TermControlAutomationPeer::SignalTextChanged()
     {
+        UiaTracing::Signal::TextChanged();
         Dispatcher().RunAsync(Windows::UI::Core::CoreDispatcherPriority::Normal, [&]() {
             // The event that is raised when textual content is modified.
             RaiseAutomationEvent(AutomationEvents::TextPatternOnTextChanged);
@@ -72,9 +75,15 @@ namespace winrt::Microsoft::Terminal::TerminalControl::implementation
     // - <none>
     void TermControlAutomationPeer::SignalCursorChanged()
     {
+        UiaTracing::Signal::CursorChanged();
         Dispatcher().RunAsync(Windows::UI::Core::CoreDispatcherPriority::Normal, [&]() {
             // The event that is raised when the text was changed in an edit control.
-            RaiseAutomationEvent(AutomationEvents::TextEditTextChanged);
+            // Do NOT fire a TextEditTextChanged. Generally, an app on the other side
+            //    will expect more information. Though you can dispatch that event
+            //    on its own, it may result in a nullptr exception on the other side
+            //    because no additional information was provided. Crashing the screen
+            //    reader.
+            RaiseAutomationEvent(AutomationEvents::TextPatternOnTextSelectionChanged);
         });
     }
 

src/renderer/uia/UiaRenderer.cpp

@@ -17,6 +17,8 @@ UiaEngine::UiaEngine(IUiaEventDispatcher* dispatcher) :
     _dispatcher{ THROW_HR_IF_NULL(E_INVALIDARG, dispatcher) },
     _isPainting{ false },
     _selectionChanged{ false },
+    _textBufferChanged{ false },
+    _cursorChanged{ false },
     _isEnabled{ true },
     _prevSelection{},
     RenderEngineBase()
@@ -56,7 +58,8 @@ UiaEngine::UiaEngine(IUiaEventDispatcher* dispatcher) :
 // - S_OK, else an appropriate HRESULT for failing to allocate or write.
 [[nodiscard]] HRESULT UiaEngine::Invalidate(const SMALL_RECT* const /*psrRegion*/) noexcept
 {
-    return S_FALSE;
+    _textBufferChanged = true;
+    return S_OK;
 }
 
 // Routine Description:
@@ -68,6 +71,7 @@ UiaEngine::UiaEngine(IUiaEventDispatcher* dispatcher) :
 // - S_FALSE
 [[nodiscard]] HRESULT UiaEngine::InvalidateCursor(const COORD* const /*pcoordCursor*/) noexcept
 {
+    _cursorChanged = true;
     return S_FALSE;
 }
 
@@ -150,7 +154,8 @@ UiaEngine::UiaEngine(IUiaEventDispatcher* dispatcher) :
 // - S_OK, else an appropriate HRESULT for failing to allocate or write.
 [[nodiscard]] HRESULT UiaEngine::InvalidateAll() noexcept
 {
-    return S_FALSE;
+    _textBufferChanged = true;
+    return S_OK;
 }
 
 // Routine Description:
@@ -192,10 +197,10 @@ UiaEngine::UiaEngine(IUiaEventDispatcher* dispatcher) :
     RETURN_HR_IF(S_FALSE, !_isEnabled);
 
     // add more events here
-    // bool somethingToDo = _selectionChanged;
+    const bool somethingToDo = _selectionChanged || _textBufferChanged || _cursorChanged;
 
     // If there's nothing to do, quick return
-    RETURN_HR_IF(S_FALSE, !_selectionChanged);
+    RETURN_HR_IF(S_FALSE, !somethingToDo);
 
     _isPainting = true;
     return S_OK;
@@ -221,8 +226,26 @@ UiaEngine::UiaEngine(IUiaEventDispatcher* dispatcher) :
         }
         CATCH_LOG();
     }
+    if (_textBufferChanged)
+    {
+        try
+        {
+            _dispatcher->SignalTextChanged();
+        }
+        CATCH_LOG();
+    }
+    if (_cursorChanged)
+    {
+        try
+        {
+            _dispatcher->SignalCursorChanged();
+        }
+        CATCH_LOG();
+    }
 
     _selectionChanged = false;
+    _textBufferChanged = false;
+    _cursorChanged = false;
     _prevSelection.clear();
     _isPainting = false;
 

src/renderer/uia/UiaRenderer.hpp

@@ -82,6 +82,8 @@ namespace Microsoft::Console::Render
         bool _isEnabled;
         bool _isPainting;
         bool _selectionChanged;
+        bool _textBufferChanged;
+        bool _cursorChanged;
 
         Microsoft::Console::Types::IUiaEventDispatcher* _dispatcher;
 

src/types/UiaTracing.cpp

@@ -613,4 +613,41 @@ void UiaTracing::TextProvider::get_SupportedTextSelection(const ScreenInfoUiaPro
             TraceLoggingLevel(WINEVENT_LEVEL_VERBOSE));
     }
 }
+
+void UiaTracing::Signal::SelectionChanged() noexcept
+{
+    EnsureRegistration();
+    if (TraceLoggingProviderEnabled(g_UiaProviderTraceProvider, WINEVENT_LEVEL_VERBOSE, 0))
+    {
+        TraceLoggingWrite(
+            g_UiaProviderTraceProvider,
+            "Signal::SelectionChanged",
+            TraceLoggingLevel(WINEVENT_LEVEL_VERBOSE));
+    }
+}
+
+void UiaTracing::Signal::TextChanged() noexcept
+{
+    EnsureRegistration();
+    if (TraceLoggingProviderEnabled(g_UiaProviderTraceProvider, WINEVENT_LEVEL_VERBOSE, 0))
+    {
+        TraceLoggingWrite(
+            g_UiaProviderTraceProvider,
+            "Signal::TextChanged",
+            TraceLoggingLevel(WINEVENT_LEVEL_VERBOSE));
+    }
+}
+
+void UiaTracing::Signal::CursorChanged() noexcept
+{
+    EnsureRegistration();
+    if (TraceLoggingProviderEnabled(g_UiaProviderTraceProvider, WINEVENT_LEVEL_VERBOSE, 0))
+    {
+        TraceLoggingWrite(
+            g_UiaProviderTraceProvider,
+            "Signal::CursorChanged",
+            TraceLoggingLevel(WINEVENT_LEVEL_VERBOSE));
+    }
+}
+
 #pragma warning(pop)

src/types/UiaTracing.h

@@ -72,6 +72,14 @@ namespace Microsoft::Console::Types
             static void get_SupportedTextSelection(const ScreenInfoUiaProviderBase& base, SupportedTextSelection result) noexcept;
         };
 
+        class Signal final
+        {
+        public:
+            static void SelectionChanged() noexcept;
+            static void TextChanged() noexcept;
+            static void CursorChanged() noexcept;
+        };
+
     private:
         // Implement this as a singleton class.
         static UiaTracing& EnsureRegistration() noexcept