Accessibility: NVDA emits errors in WT1.15 preview

[LeonarddeR]

Windows Terminal version

1.15.2283.0

Windows build number

25188.1000

Other Software

NVDA 2022.2.2

Steps to reproduce

1. Open bash in windows terminal
2. type nano /etc/hosts

Expected Behavior

No error in NVDA

Actual Behavior

NVDA emits the following error:

ERROR - NVDAObjects.behaviors.LiveText._monitor (18:21:06.798) - Dynamic_WinTerminalUIAEditableTextWithAutoSelectDetectionUIA._monitorThread (22344):
Error getting or calculating new text
Traceback (most recent call last):
  File "NVDAObjects\behaviors.pyc", line 386, in _monitor
  File "NVDAObjects\behaviors.pyc", line 350, in _getText
  File "diffHandler.pyc", line 62, in _getText
  File "baseObject.pyc", line 26, in __get__
  File "NVDAObjects\UIA\__init__.pyc", line 848, in _get_text
  File "NVDAObjects\UIA\__init__.pyc", line 555, in _getTextFromUIARange
  File "monkeyPatches\comtypesMonkeyPatches.pyc", line 32, in __call__
_ctypes.COMError: (-2147467259, 'Unspecified error', (None, None, None, 0, None))

I wasn't able to reproduce this with WT1.14, so therefore I'm filing this here since there might be a regression in UIA related code. @codeofdusk could you reproduce this?

[codeofdusk]

I've also seen this, but not with wtNotifications.

This is probably related to broken assumptions when switching to/from the alt buffer.

[LeonarddeR]

This error indeed has nothing to do with the notifications implementation.

CC @carlos-zamora just want to make sure that this bug doesn't end up in a release, since that would be annoying for many sr users.

[carlos-zamora]

@LeonarddeR (or @codeofdusk since you're familiar with the space) I think I need a little more context here. It looks like NVDA is calling the UIA API GetText() off of a TextRange. That corresponds to the following code in Windows Terminal:

terminal/src/types/UiaTextRangeBase.cpp

Lines 954 to 1023 in f2a6918

	IFACEMETHODIMP UiaTextRangeBase::GetText(_In_ int maxLength, _Out_ BSTR* pRetVal) noexcept
	try
	{
	RETURN_HR_IF_NULL(E_INVALIDARG, pRetVal);
	RETURN_HR_IF(E_INVALIDARG, maxLength < -1);
	*pRetVal = nullptr;
	_pData->LockConsole();
	auto Unlock = wil::scope_exit([&]() noexcept {
	_pData->UnlockConsole();
	});
	RETURN_HR_IF(E_FAIL, !_pData->IsUiaDataInitialized());
	const auto text = _getTextValue(maxLength);
	Unlock.reset();
	*pRetVal = SysAllocString(text.c_str());
	RETURN_HR_IF_NULL(E_OUTOFMEMORY, *pRetVal);
	UiaTracing::TextRange::GetText(*this, maxLength, text);
	return S_OK;
	}
	CATCH_RETURN();
	// Method Description:
	// - Helper method for GetText(). Retrieves the text that the UiaTextRange encompasses as a wstring
	// Arguments:
	// - maxLength - the maximum size of the retrieved text. nullopt means we don't care about the size.
	// Return Value:
	// - the text that the UiaTextRange encompasses
	#pragma warning(push)
	#pragma warning(disable : 26447) // compiler isn't filtering throws inside the try/catch
	std::wstring UiaTextRangeBase::_getTextValue(til::CoordType maxLength) const
	{
	std::wstring textData{};
	if (!IsDegenerate())
	{
	const auto& buffer = _pData->GetTextBuffer();
	const auto bufferSize = buffer.GetSize();
	// TODO GH#5406: create a different UIA parent object for each TextBuffer
	// nvaccess/nvda#11428: Ensure our endpoints are in bounds
	// otherwise, we'll FailFast catastrophically
	THROW_HR_IF(E_FAIL, !bufferSize.IsInBounds(_start) || !bufferSize.IsInBounds(_end));
	// convert _end to be inclusive
	auto inclusiveEnd = _end;
	bufferSize.DecrementInBounds(inclusiveEnd, true);
	const auto textRects = buffer.GetTextRects(_start, inclusiveEnd, _blockRange, true);
	const auto bufferData = buffer.GetText(true,
	false,
	textRects);
	const size_t textDataSize = bufferData.text.size() * bufferSize.Width();
	textData.reserve(textDataSize);
	for (const auto& text : bufferData.text)
	{
	textData += text;
	}
	}
	if (maxLength >= 0)
	{
	textData.resize(maxLength);
	}
	return textData;
	}
	#pragma warning(pop)

It looks like we emit an error if...

1. the second parameter (the out param) wasn't provided properly
2. the first parameter (dictating the max length) is less than -1
3. the newly created terminal content isn't fully initialized yet
4. we're out of memory and we can't create the string result to return
5. (as @codeofdusk said) the text range points to content that doesn't exist (this is a quick-n-easy way to invalidate a text range that was on the alt buffer when we're now on the main buffer)

I assume the main culprit here is number 5, but to be certain, could you provide the following:

• What UIA APIs was NVDA calling? Obviously GetText() is the one that returns an error, but what were the calls leading up to that.
• If you can explain how I can get a trace from NVDA, that'd be even better.

[carlos-zamora]

Yeah, that error code is E_FAIL so it's 100% that alt buffer thing.

[ghost]

🎉This issue was addressed in #13907, which has now been successfully released as Windows Terminal v1.15.252.:tada:

Handy links:

• Release Notes
• Store Download

[ghost]

🎉This issue was addressed in #13907, which has now been successfully released as Windows Terminal Preview v1.16.252.:tada:

Handy links:

• Release Notes
• Store Download