[a11y] Ensure buffer is initialized before interacting with it (#11312)

Adds a check before every UIA function call to ensure the terminal (specifically the buffer) is initialized before doing work. Both the `ScreenInfoUiaProvider` and the `UiaTextRange` are now covered.

## References
Closes #11135 
#10971 & #11042

## Detailed Description of the Pull Request / Additional comments
Originally, I tried applying this heuristic to all the `RuntimeClassInitialize` on `UiaTextRangeBase` with the philosophy of "a range pointing to an invalid buffer is invalid itself", but that caused a regression on [MSFT 33353327](https://microsoft.visualstudio.com/OS/_workitems/edit/33353327).

`IUiaData` also has `GetTextBuffer()` return a `TextBuffer&`, which cannot be checked for nullness. Instead, I decided to add a function to `IUiaData` that checks if we have a valid state. Since this is shared with Conhost and Conhost doesn't have this issue, I simply make that function say that it's always in a valid state.

## Validation Steps Performed
- [X] Narrator can detect newly created terminals
- [X] (On Windows Server 2022) Windows Terminal does not hang on launch

src/Terminal.wprp

@@ -12,6 +12,7 @@
     <EventProvider Id="EventProvider_TerminalWin32Host" Name="56c06166-2e2e-5f4d-7ff3-74f4b78c87d6" />
     <EventProvider Id="EventProvider_TerminalRemoting" Name="d6f04aad-629f-539a-77c1-73f5c3e4aa7b" />
     <EventProvider Id="EventProvider_TerminalDirectX" Name="c93e739e-ae50-5a14-78e7-f171e947535d" />
+    <EventProvider Id="EventProvider_TerminalUIA" Name="e7ebce59-2161-572d-b263-2f16a6afb9e5"/>
     <Profile Id="Terminal.Verbose.File" Name="Terminal" Description="Terminal" LoggingMode="File" DetailLevel="Verbose">
       <Collectors>
         <EventCollectorId Value="EventCollector_Terminal">
@@ -23,6 +24,7 @@
             <EventProviderId Value="EventProvider_TerminalWin32Host" />
             <EventProviderId Value="EventProvider_TerminalRemoting" />
             <EventProviderId Value="EventProvider_TerminalDirectX" />
+            <EventProviderId Value="EventProvider_TerminalUIA" />
           </EventProviders>
         </EventCollectorId>
       </Collectors>

src/cascadia/TerminalCore/Terminal.hpp

@@ -199,6 +199,7 @@ class Microsoft::Terminal::Core::Terminal final :
     const COORD GetSelectionEnd() const noexcept override;
     const std::wstring_view GetConsoleTitle() const noexcept override;
     void ColorSelection(const COORD coordSelectionStart, const COORD coordSelectionEnd, const TextAttribute) override;
+    const bool IsUiaDataInitialized() const noexcept override;
 #pragma endregion
 
     void SetWriteInputCallback(std::function<void(std::wstring&)> pfn) noexcept;

src/cascadia/TerminalCore/terminalrenderdata.cpp

@@ -250,3 +250,12 @@ bool Terminal::IsScreenReversed() const noexcept
 {
     return _screenReversed;
 }
+
+const bool Terminal::IsUiaDataInitialized() const noexcept
+{
+    // GH#11135: Windows Terminal needs to create and return an automation peer
+    // when a screen reader requests it. However, the terminal might not be fully
+    // initialized yet. So we use this to check if any crucial components of
+    // UiaData are not yet initialized.
+    return !!_buffer;
+}

src/host/renderData.hpp

@@ -69,5 +69,6 @@ class RenderData final :
     const COORD GetSelectionAnchor() const noexcept;
     const COORD GetSelectionEnd() const noexcept;
     void ColorSelection(const COORD coordSelectionStart, const COORD coordSelectionEnd, const TextAttribute attr);
+    const bool IsUiaDataInitialized() const noexcept override { return true; }
 #pragma endregion
 };

src/host/ut_host/VtIoTests.cpp

@@ -392,6 +392,11 @@ class MockRenderData : public IRenderData, IUiaData
     {
     }
 
+    const bool IsUiaDataInitialized() const noexcept
+    {
+        return true;
+    }
+
     const std::wstring GetHyperlinkUri(uint16_t /*id*/) const noexcept
     {
         return {};

src/types/IUiaData.h

@@ -40,6 +40,7 @@ namespace Microsoft::Console::Types
         virtual const COORD GetSelectionAnchor() const noexcept = 0;
         virtual const COORD GetSelectionEnd() const noexcept = 0;
         virtual void ColorSelection(const COORD coordSelectionStart, const COORD coordSelectionEnd, const TextAttribute attr) = 0;
+        virtual const bool IsUiaDataInitialized() const noexcept = 0;
     };
 
     // See docs/virtual-dtors.md for an explanation of why this is weird.

src/types/ScreenInfoUiaProviderBase.cpp

@@ -220,21 +220,19 @@ IFACEMETHODIMP ScreenInfoUiaProviderBase::SetFocus()
 
 IFACEMETHODIMP ScreenInfoUiaProviderBase::GetSelection(_Outptr_result_maybenull_ SAFEARRAY** ppRetVal)
 {
+    RETURN_HR_IF_NULL(E_INVALIDARG, ppRetVal);
+    *ppRetVal = nullptr;
+
     _LockConsole();
     auto Unlock = wil::scope_exit([&]() noexcept {
         _UnlockConsole();
     });
-
-    RETURN_HR_IF_NULL(E_INVALIDARG, ppRetVal);
-    *ppRetVal = nullptr;
-    HRESULT hr = S_OK;
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
 
     // make a safe array
+    HRESULT hr = S_OK;
     *ppRetVal = SafeArrayCreateVector(VT_UNKNOWN, 0, 1);
-    if (*ppRetVal == nullptr)
-    {
-        return E_OUTOFMEMORY;
-    }
+    RETURN_HR_IF_NULL(E_OUTOFMEMORY, *ppRetVal);
 
     WRL::ComPtr<UiaTextRangeBase> range;
     if (!_pData->IsSelectionActive())
@@ -272,19 +270,18 @@ IFACEMETHODIMP ScreenInfoUiaProviderBase::GetSelection(_Outptr_result_maybenull_
 
 IFACEMETHODIMP ScreenInfoUiaProviderBase::GetVisibleRanges(_Outptr_result_maybenull_ SAFEARRAY** ppRetVal)
 {
+    RETURN_HR_IF_NULL(E_INVALIDARG, ppRetVal);
+    *ppRetVal = nullptr;
+
     _LockConsole();
     auto Unlock = wil::scope_exit([&]() noexcept {
         _UnlockConsole();
     });
-
-    RETURN_HR_IF_NULL(E_INVALIDARG, ppRetVal);
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
 
     // make a safe array
     *ppRetVal = SafeArrayCreateVector(VT_UNKNOWN, 0, 1);
-    if (*ppRetVal == nullptr)
-    {
-        return E_OUTOFMEMORY;
-    }
+    RETURN_HR_IF_NULL(E_OUTOFMEMORY, *ppRetVal);
 
     WRL::ComPtr<UiaTextRangeBase> range;
     const auto bufferSize = _pData->GetTextBuffer().GetSize();

src/types/TermControlUiaProvider.cpp

@@ -16,21 +16,13 @@ HRESULT TermControlUiaProvider::RuntimeClassInitialize(_In_ ::Microsoft::Console
     RETURN_IF_FAILED(ScreenInfoUiaProviderBase::RuntimeClassInitialize(uiaData));
 
     _controlInfo = controlInfo;
-
-    // TODO GitHub #1914: Re-attach Tracing to UIA Tree
-    //Tracing::s_TraceUia(nullptr, ApiCall::Constructor, nullptr);
     return S_OK;
 }
 
 IFACEMETHODIMP TermControlUiaProvider::Navigate(_In_ NavigateDirection direction,
                                                 _COM_Outptr_result_maybenull_ IRawElementProviderFragment** ppProvider) noexcept
 {
     RETURN_HR_IF_NULL(E_INVALIDARG, ppProvider);
-
-    // TODO GitHub #1914: Re-attach Tracing to UIA Tree
-    /*ApiMsgNavigate apiMsg;
-    apiMsg.Direction = direction;
-    Tracing::s_TraceUia(this, ApiCall::Navigate, &apiMsg);*/
     *ppProvider = nullptr;
 
     if (direction == NavigateDirection_Parent)
@@ -122,6 +114,12 @@ HRESULT TermControlUiaProvider::GetSelectionRange(_In_ IRawElementProviderSimple
     RETURN_HR_IF_NULL(E_INVALIDARG, ppUtr);
     *ppUtr = nullptr;
 
+    _pData->LockConsole();
+    auto Unlock = wil::scope_exit([&]() noexcept {
+        _pData->UnlockConsole();
+    });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized() || !_pData->IsSelectionActive());
+
     const auto start = _pData->GetSelectionAnchor();
 
     // we need to make end exclusive

src/types/TermControlUiaTextRange.cpp

@@ -63,20 +63,6 @@ IFACEMETHODIMP TermControlUiaTextRange::Clone(_Outptr_result_maybenull_ ITextRan
         return hr;
     }
 
-#if defined(_DEBUG) && defined(UiaTextRangeBase_DEBUG_MSGS)
-    OutputDebugString(L"Clone\n");
-    std::wstringstream ss;
-    ss << _id << L" cloned to " << (static_cast<UiaTextRangeBase*>(*ppRetVal))->_id;
-    std::wstring str = ss.str();
-    OutputDebugString(str.c_str());
-    OutputDebugString(L"\n");
-#endif
-    // TODO GitHub #1914: Re-attach Tracing to UIA Tree
-    // tracing
-    /*ApiMsgClone apiMsg;
-    apiMsg.CloneId = static_cast<UiaTextRangeBase*>(*ppRetVal)->GetId();
-    Tracing::s_TraceUia(this, ApiCall::Clone, &apiMsg);*/
-
     return S_OK;
 }
 

src/types/UiaTextRangeBase.cpp

@@ -220,15 +220,18 @@ IFACEMETHODIMP UiaTextRangeBase::CompareEndpoints(_In_ TextPatternRangeEndpoint
                                                   _Out_ int* pRetVal) noexcept
 try
 {
-    RETURN_HR_IF(E_INVALIDARG, pRetVal == nullptr);
+    RETURN_HR_IF_NULL(E_INVALIDARG, pRetVal);
     *pRetVal = 0;
 
+    _pData->LockConsole();
+    auto Unlock = wil::scope_exit([&]() noexcept {
+        _pData->UnlockConsole();
+    });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
+
     // get the text range that we're comparing to
     const UiaTextRangeBase* range = static_cast<UiaTextRangeBase*>(pTargetRange);
-    if (range == nullptr)
-    {
-        return E_INVALIDARG;
-    }
+    RETURN_HR_IF_NULL(E_INVALIDARG, range);
 
     // get endpoint value that we're comparing to
     const auto other = range->GetEndpoint(targetEndpoint);
@@ -240,10 +243,7 @@ try
     //   This is a temporary solution to comparing two UTRs from different TextBuffers
     //   Ensure both endpoints fit in the current buffer.
     const auto bufferSize = _pData->GetTextBuffer().GetSize();
-    if (!bufferSize.IsInBounds(mine, true) || !bufferSize.IsInBounds(other, true))
-    {
-        return E_FAIL;
-    }
+    RETURN_HR_IF(E_FAIL, !bufferSize.IsInBounds(mine, true) || !bufferSize.IsInBounds(other, true));
 
     // compare them
     *pRetVal = bufferSize.CompareInBounds(mine, other, true);
@@ -259,6 +259,7 @@ IFACEMETHODIMP UiaTextRangeBase::ExpandToEnclosingUnit(_In_ TextUnit unit) noexc
     auto Unlock = wil::scope_exit([&]() noexcept {
         _pData->UnlockConsole();
     });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
 
     try
     {
@@ -446,6 +447,12 @@ try
     RETURN_HR_IF(E_INVALIDARG, ppRetVal == nullptr);
     *ppRetVal = nullptr;
 
+    _pData->LockConsole();
+    auto Unlock = wil::scope_exit([&]() noexcept {
+        _pData->UnlockConsole();
+    });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
+
     // AttributeIDs that require special handling
     switch (attributeId)
     {
@@ -607,6 +614,12 @@ try
     RETURN_HR_IF(E_INVALIDARG, ppRetVal == nullptr);
     *ppRetVal = nullptr;
 
+    _pData->LockConsole();
+    auto Unlock = wil::scope_exit([&]() noexcept {
+        _pData->UnlockConsole();
+    });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
+
     const std::wstring queryText{ text, SysStringLen(text) };
     const auto bufferSize = _getBufferSize();
     const auto sensitivity = ignoreCase ? Search::Sensitivity::CaseInsensitive : Search::Sensitivity::CaseSensitive;
@@ -732,6 +745,12 @@ try
     RETURN_HR_IF(E_INVALIDARG, pRetVal == nullptr);
     VariantInit(pRetVal);
 
+    _pData->LockConsole();
+    auto Unlock = wil::scope_exit([&]() noexcept {
+        _pData->UnlockConsole();
+    });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
+
     // AttributeIDs that require special handling
     switch (attributeId)
     {
@@ -819,13 +838,14 @@ CATCH_RETURN();
 
 IFACEMETHODIMP UiaTextRangeBase::GetBoundingRectangles(_Outptr_result_maybenull_ SAFEARRAY** ppRetVal) noexcept
 {
+    RETURN_HR_IF(E_INVALIDARG, ppRetVal == nullptr);
+    *ppRetVal = nullptr;
+
     _pData->LockConsole();
     auto Unlock = wil::scope_exit([&]() noexcept {
         _pData->UnlockConsole();
     });
-
-    RETURN_HR_IF(E_INVALIDARG, ppRetVal == nullptr);
-    *ppRetVal = nullptr;
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
 
     try
     {
@@ -927,21 +947,19 @@ CATCH_RETURN();
 IFACEMETHODIMP UiaTextRangeBase::GetText(_In_ int maxLength, _Out_ BSTR* pRetVal) noexcept
 try
 {
-    RETURN_HR_IF(E_INVALIDARG, pRetVal == nullptr);
+    RETURN_HR_IF_NULL(E_INVALIDARG, pRetVal);
+    RETURN_HR_IF(E_INVALIDARG, maxLength < -1);
     *pRetVal = nullptr;
 
-    if (maxLength < -1)
-    {
-        return E_INVALIDARG;
-    }
+    _pData->LockConsole();
+    auto Unlock = wil::scope_exit([&]() noexcept {
+        _pData->UnlockConsole();
+    });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
 
     const auto maxLengthOpt = (maxLength == -1) ?
                                   std::nullopt :
                                   std::optional<unsigned int>{ maxLength };
-    _pData->LockConsole();
-    auto Unlock = wil::scope_exit([this]() noexcept {
-        _pData->UnlockConsole();
-    });
     const auto text = _getTextValue(maxLengthOpt);
     Unlock.reset();
 
@@ -1015,6 +1033,7 @@ try
     auto Unlock = wil::scope_exit([&]() noexcept {
         _pData->UnlockConsole();
     });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
 
     const auto wasDegenerate = IsDegenerate();
     if (count != 0)
@@ -1070,15 +1089,13 @@ IFACEMETHODIMP UiaTextRangeBase::MoveEndpointByUnit(_In_ TextPatternRangeEndpoin
 {
     RETURN_HR_IF(E_INVALIDARG, pRetVal == nullptr);
     *pRetVal = 0;
-    if (count == 0)
-    {
-        return S_OK;
-    }
 
     _pData->LockConsole();
     auto Unlock = wil::scope_exit([&]() noexcept {
         _pData->UnlockConsole();
     });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
+    RETURN_HR_IF(S_OK, count == 0);
 
     try
     {
@@ -1116,21 +1133,16 @@ try
     });
 
     const UiaTextRangeBase* range = static_cast<UiaTextRangeBase*>(pTargetRange);
-    if (range == nullptr)
-    {
-        return E_INVALIDARG;
-    }
+    RETURN_HR_IF_NULL(E_INVALIDARG, range);
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
 
     // TODO GH#5406: create a different UIA parent object for each TextBuffer
     //   This is a temporary solution to comparing two UTRs from different TextBuffers
     //   Ensure both endpoints fit in the current buffer.
     const auto bufferSize = _pData->GetTextBuffer().GetSize();
     const auto mine = GetEndpoint(endpoint);
     const auto other = range->GetEndpoint(targetEndpoint);
-    if (!bufferSize.IsInBounds(mine, true) || !bufferSize.IsInBounds(other, true))
-    {
-        return E_FAIL;
-    }
+    RETURN_HR_IF(E_FAIL, !bufferSize.IsInBounds(mine, true) || !bufferSize.IsInBounds(other, true));
 
     SetEndpoint(endpoint, range->GetEndpoint(targetEndpoint));
 
@@ -1146,6 +1158,7 @@ try
     auto Unlock = wil::scope_exit([&]() noexcept {
         _pData->UnlockConsole();
     });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
 
     if (IsDegenerate())
     {
@@ -1190,6 +1203,7 @@ try
     auto Unlock = wil::scope_exit([&]() noexcept {
         _pData->UnlockConsole();
     });
+    RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
 
     const auto oldViewport = _pData->GetViewport().ToInclusive();
     const auto viewportHeight = _getViewportHeight(oldViewport);