Fix macro parser

src/terminal/adapter/ITermDispatch.hpp

@@ -23,7 +23,7 @@ namespace Microsoft::Console::VirtualTerminal
 class Microsoft::Console::VirtualTerminal::ITermDispatch
 {
 public:
-    using StringHandler = std::function<bool(const wchar_t)>;
+    using StringHandler = std::function<bool(std::wstring_view)>;
 
     enum class OptionalFeature
     {

src/terminal/adapter/MacroBuffer.cpp

@@ -113,92 +113,96 @@ bool MacroBuffer::InitParser(const size_t macroId, const DispatchTypes::MacroDel
     return false;
 }
 
-bool MacroBuffer::ParseDefinition(const wchar_t ch)
+bool MacroBuffer::ParseDefinition(const std::wstring_view str)
 {
-    // Once we receive an ESC, that marks the end of the definition, but if
-    // an unterminated repeat is still pending, we should apply that now.
-    if (ch == AsciiChars::ESC)
+    for (const auto ch : str)
     {
-        if (_repeatPending && !_applyPendingRepeat())
+        // Once we receive an ESC, that marks the end of the definition, but if
+        // an unterminated repeat is still pending, we should apply that now.
+        if (ch == AsciiChars::ESC)
+        {
+            if (_repeatPending && !_applyPendingRepeat())
+            {
+                _deleteMacro(_activeMacro());
+            }
+            return false;
+        }
+
+        // Any other control characters are just ignored.
+        if (ch < L' ')
+        {
+            continue;
+        }
+
+        // For "text encoded" macros, we'll always be in the ExpectingText state.
+        // For "hex encoded" macros, we'll typically be alternating between the
+        // ExpectingHexDigit and ExpectingSecondHexDigit states as we parse the two
+        // digits of each hex pair. But we also need to deal with repeat sequences,
+        // which start with `!`, followed by a numeric repeat count, and then a
+        // range of hex pairs between two `;` characters. When parsing the repeat
+        // count, we use the ExpectingRepeatCount state, but when parsing the hex
+        // pairs of the repeat, we just use the regular ExpectingHexDigit states.
+
+        auto success = true;
+        switch (_parseState)
+        {
+        case State::ExpectingText:
+            success = _appendToActiveMacro(ch);
+            break;
+        case State::ExpectingHexDigit:
+            if (_decodeHexDigit(ch))
+            {
+                _parseState = State::ExpectingSecondHexDigit;
+            }
+            else if (ch == L'!' && !_repeatPending)
+            {
+                _parseState = State::ExpectingRepeatCount;
+                _repeatCount = 0;
+            }
+            else if (ch == L';' && _repeatPending)
+            {
+                success = _applyPendingRepeat();
+            }
+            else
+            {
+                success = false;
+            }
+            break;
+        case State::ExpectingSecondHexDigit:
+            success = _decodeHexDigit(ch) && _appendToActiveMacro(_decodedChar);
+            _decodedChar = 0;
+            _parseState = State::ExpectingHexDigit;
+            break;
+        case State::ExpectingRepeatCount:
+            if (ch >= L'0' && ch <= L'9')
+            {
+                _repeatCount = _repeatCount * 10 + (ch - L'0');
+                _repeatCount = std::min<size_t>(_repeatCount, MAX_PARAMETER_VALUE);
+            }
+            else if (ch == L';')
+            {
+                _repeatPending = true;
+                _repeatStart = _activeMacro().length();
+                _parseState = State::ExpectingHexDigit;
+            }
+            else
+            {
+                success = false;
+            }
+            break;
+        default:
+            success = false;
+            break;
+        }
+
+        // If there is an error in the definition, clear everything received so far.
+        if (!success)
         {
             _deleteMacro(_activeMacro());
+            return false;
         }
-        return false;
     }
-
-    // Any other control characters are just ignored.
-    if (ch < L' ')
-    {
-        return true;
-    }
-
-    // For "text encoded" macros, we'll always be in the ExpectingText state.
-    // For "hex encoded" macros, we'll typically be alternating between the
-    // ExpectingHexDigit and ExpectingSecondHexDigit states as we parse the two
-    // digits of each hex pair. But we also need to deal with repeat sequences,
-    // which start with `!`, followed by a numeric repeat count, and then a
-    // range of hex pairs between two `;` characters. When parsing the repeat
-    // count, we use the ExpectingRepeatCount state, but when parsing the hex
-    // pairs of the repeat, we just use the regular ExpectingHexDigit states.
-
-    auto success = true;
-    switch (_parseState)
-    {
-    case State::ExpectingText:
-        success = _appendToActiveMacro(ch);
-        break;
-    case State::ExpectingHexDigit:
-        if (_decodeHexDigit(ch))
-        {
-            _parseState = State::ExpectingSecondHexDigit;
-        }
-        else if (ch == L'!' && !_repeatPending)
-        {
-            _parseState = State::ExpectingRepeatCount;
-            _repeatCount = 0;
-        }
-        else if (ch == L';' && _repeatPending)
-        {
-            success = _applyPendingRepeat();
-        }
-        else
-        {
-            success = false;
-        }
-        break;
-    case State::ExpectingSecondHexDigit:
-        success = _decodeHexDigit(ch) && _appendToActiveMacro(_decodedChar);
-        _decodedChar = 0;
-        _parseState = State::ExpectingHexDigit;
-        break;
-    case State::ExpectingRepeatCount:
-        if (ch >= L'0' && ch <= L'9')
-        {
-            _repeatCount = _repeatCount * 10 + (ch - L'0');
-            _repeatCount = std::min<size_t>(_repeatCount, MAX_PARAMETER_VALUE);
-        }
-        else if (ch == L';')
-        {
-            _repeatPending = true;
-            _repeatStart = _activeMacro().length();
-            _parseState = State::ExpectingHexDigit;
-        }
-        else
-        {
-            success = false;
-        }
-        break;
-    default:
-        success = false;
-        break;
-    }
-
-    // If there is an error in the definition, clear everything received so far.
-    if (!success)
-    {
-        _deleteMacro(_activeMacro());
-    }
-    return success;
+    return true;
 }
 
 bool MacroBuffer::_decodeHexDigit(const wchar_t ch) noexcept

src/terminal/adapter/MacroBuffer.hpp

@@ -44,7 +44,7 @@ namespace Microsoft::Console::VirtualTerminal
         void InvokeMacro(const size_t macroId, StateMachine& stateMachine);
         void ClearMacrosIfInUse();
         bool InitParser(const size_t macroId, const DispatchTypes::MacroDeleteControl deleteControl, const DispatchTypes::MacroEncoding encoding);
-        bool ParseDefinition(const wchar_t ch);
+        bool ParseDefinition(std::wstring_view str);
 
     private:
         bool _decodeHexDigit(const wchar_t ch) noexcept;

src/terminal/adapter/SixelParser.cpp

@@ -42,9 +42,8 @@ size_t SixelParser::MaxColorsForLevel(const VTInt conformanceLevel) noexcept
     }
 }
 
-SixelParser::SixelParser(AdaptDispatch& dispatcher, const StateMachine& stateMachine, const VTInt conformanceLevel) noexcept :
+SixelParser::SixelParser(AdaptDispatch& dispatcher, const VTInt conformanceLevel) noexcept :
     _dispatcher{ dispatcher },
-    _stateMachine{ stateMachine },
     _conformanceLevel{ conformanceLevel },
     _cellSize{ CellSizeForLevel(conformanceLevel) },
     _maxColors{ MaxColorsForLevel(conformanceLevel) }
@@ -80,7 +79,7 @@ void SixelParser::SetDisplayMode(const bool enabled) noexcept
     }
 }
 
-std::function<bool(wchar_t)> SixelParser::DefineImage(const VTInt macroParameter, const DispatchTypes::SixelBackground backgroundSelect, const VTParameter backgroundColor)
+std::function<bool(std::wstring_view)> SixelParser::DefineImage(const VTInt macroParameter, const DispatchTypes::SixelBackground backgroundSelect, const VTParameter backgroundColor)
 {
     if (_initTextBufferBoundaries())
     {
@@ -89,8 +88,17 @@ std::function<bool(wchar_t)> SixelParser::DefineImage(const VTInt macroParameter
         _initImageBuffer();
         _state = States::Normal;
         _parameters.clear();
-        return [&](const auto ch) {
-            _parseCommandChar(ch);
+        return [&](const std::wstring_view str) {
+            auto it = str.begin();
+            const auto end = str.end();
+
+            while (it != end)
+            {
+                const auto ch = *it++;
+                _isProcessingLastCharacter = it == end;
+                _parseCommandChar(ch);
+            }
+
             return true;
         };
     }
@@ -554,7 +562,7 @@ void SixelParser::_defineColor(const size_t colorNumber, const COLORREF color)
         // If some image content has already been defined at this point, and
         // we're processing the last character in the packet, this is likely an
         // attempt to animate the palette, so we should flush the image.
-        if (_imageWidth > 0 && _stateMachine.IsProcessingLastCharacter())
+        if (_imageWidth > 0 && _isProcessingLastCharacter)
         {
             _maybeFlushImageBuffer();
         }
@@ -876,7 +884,7 @@ void SixelParser::_maybeFlushImageBuffer(const bool endOfSequence)
     const auto currentTime = steady_clock::now();
     const auto timeSinceLastFlush = duration_cast<milliseconds>(currentTime - _lastFlushTime);
     const auto linesSinceLastFlush = _imageLineCount - _lastFlushLine;
-    if (endOfSequence || timeSinceLastFlush > 500ms || (linesSinceLastFlush <= 1 && _stateMachine.IsProcessingLastCharacter()))
+    if (endOfSequence || timeSinceLastFlush > 500ms || (linesSinceLastFlush <= 1 && _isProcessingLastCharacter))
     {
         _lastFlushTime = currentTime;
         _lastFlushLine = _imageLineCount;

src/terminal/adapter/SixelParser.hpp

@@ -21,7 +21,6 @@ namespace Microsoft::Console::VirtualTerminal
 {
     class AdaptDispatch;
     class Page;
-    class StateMachine;
 
     class SixelParser
     {
@@ -31,10 +30,10 @@ namespace Microsoft::Console::VirtualTerminal
         static til::size CellSizeForLevel(const VTInt conformanceLevel = DefaultConformance) noexcept;
         static size_t MaxColorsForLevel(const VTInt conformanceLevel = DefaultConformance) noexcept;
 
-        SixelParser(AdaptDispatch& dispatcher, const StateMachine& stateMachine, const VTInt conformanceLevel = DefaultConformance) noexcept;
+        SixelParser(AdaptDispatch& dispatcher, const VTInt conformanceLevel = DefaultConformance) noexcept;
         void SoftReset();
         void SetDisplayMode(const bool enabled) noexcept;
-        std::function<bool(wchar_t)> DefineImage(const VTInt macroParameter, const DispatchTypes::SixelBackground backgroundSelect, const VTParameter backgroundColor);
+        std::function<bool(std::wstring_view)> DefineImage(const VTInt macroParameter, const DispatchTypes::SixelBackground backgroundSelect, const VTParameter backgroundColor);
 
     private:
         // NB: If we want to support more than 256 colors, we'll also need to
@@ -49,7 +48,6 @@ namespace Microsoft::Console::VirtualTerminal
         };
 
         AdaptDispatch& _dispatcher;
-        const StateMachine& _stateMachine;
         const VTInt _conformanceLevel;
 
         void _parseCommandChar(const wchar_t ch);
@@ -106,6 +104,7 @@ namespace Microsoft::Console::VirtualTerminal
         size_t _colorsAvailable = 0;
         IndexedPixel _foregroundPixel = {};
         bool _colorTableChanged = false;
+        bool _isProcessingLastCharacter = false;
 
         void _initImageBuffer();
         void _resizeImageBuffer(const til::CoordType requiredHeight);

src/terminal/adapter/adaptDispatch.cpp

@@ -3787,7 +3787,7 @@ ITermDispatch::StringHandler AdaptDispatch::DefineSixelImage(const VTInt macroPa
     // The sixel parser is created on demand.
     if (!_sixelParser)
     {
-        _sixelParser = std::make_unique<SixelParser>(*this, _api.GetStateMachine());
+        _sixelParser = std::make_unique<SixelParser>(*this);
         _sixelParser->SetDisplayMode(_modes.test(Mode::SixelDisplay));
     }
     return _sixelParser->DefineImage(macroParameter, backgroundSelect, backgroundColor);
@@ -3836,34 +3836,37 @@ ITermDispatch::StringHandler AdaptDispatch::DownloadDRCS(const VTInt fontNumber,
         return nullptr;
     }
 
-    return [=](const auto ch) {
-        // We pass the data string straight through to the font buffer class
-        // until we receive an ESC, indicating the end of the string. At that
-        // point we can finalize the buffer, and if valid, update the renderer
-        // with the constructed bit pattern.
-        if (ch != AsciiChars::ESC)
+    return [=](const std::wstring_view str) {
+        for (const auto ch : str)
         {
-            _fontBuffer->AddSixelData(ch);
-        }
-        else if (_fontBuffer->FinalizeSixelData())
-        {
-            // We also need to inform the character set mapper of the ID that
-            // will map to this font (we only support one font buffer so there
-            // will only ever be one active dynamic character set).
-            if (charsetSize == DispatchTypes::CharsetSize::Size96)
+            // We pass the data string straight through to the font buffer class
+            // until we receive an ESC, indicating the end of the string. At that
+            // point we can finalize the buffer, and if valid, update the renderer
+            // with the constructed bit pattern.
+            if (ch != AsciiChars::ESC)
             {
-                _termOutput.SetDrcs96Designation(_fontBuffer->GetDesignation());
+                _fontBuffer->AddSixelData(ch);
             }
-            else
+            else if (_fontBuffer->FinalizeSixelData())
             {
-                _termOutput.SetDrcs94Designation(_fontBuffer->GetDesignation());
-            }
-            if (_renderer)
-            {
-                const auto bitPattern = _fontBuffer->GetBitPattern();
-                const auto cellSize = _fontBuffer->GetCellSize();
-                const auto centeringHint = _fontBuffer->GetTextCenteringHint();
-                _renderer->UpdateSoftFont(bitPattern, cellSize, centeringHint);
+                // We also need to inform the character set mapper of the ID that
+                // will map to this font (we only support one font buffer so there
+                // will only ever be one active dynamic character set).
+                if (charsetSize == DispatchTypes::CharsetSize::Size96)
+                {
+                    _termOutput.SetDrcs96Designation(_fontBuffer->GetDesignation());
+                }
+                else
+                {
+                    _termOutput.SetDrcs94Designation(_fontBuffer->GetDesignation());
+                }
+                if (_renderer)
+                {
+                    const auto bitPattern = _fontBuffer->GetBitPattern();
+                    const auto cellSize = _fontBuffer->GetCellSize();
+                    const auto centeringHint = _fontBuffer->GetTextCenteringHint();
+                    _renderer->UpdateSoftFont(bitPattern, cellSize, centeringHint);
+                }
             }
         }
         return true;
@@ -3889,24 +3892,27 @@ void AdaptDispatch::RequestUserPreferenceCharset()
 // - a function to parse the character set ID
 ITermDispatch::StringHandler AdaptDispatch::AssignUserPreferenceCharset(const DispatchTypes::CharsetSize charsetSize)
 {
-    return [this, charsetSize, idBuilder = VTIDBuilder{}](const auto ch) mutable {
-        if (ch >= L'\x20' && ch <= L'\x2f')
+    return [this, charsetSize, idBuilder = VTIDBuilder{}](const std::wstring_view str) mutable {
+        for (const auto ch : str)
         {
-            idBuilder.AddIntermediate(ch);
-        }
-        else if (ch >= L'\x30' && ch <= L'\x7e')
-        {
-            const auto id = idBuilder.Finalize(ch);
-            switch (charsetSize)
+            if (ch >= L'\x20' && ch <= L'\x2f')
             {
-            case DispatchTypes::CharsetSize::Size94:
-                _termOutput.AssignUserPreferenceCharset(id, false);
-                break;
-            case DispatchTypes::CharsetSize::Size96:
-                _termOutput.AssignUserPreferenceCharset(id, true);
-                break;
+                idBuilder.AddIntermediate(ch);
+            }
+            else if (ch >= L'\x30' && ch <= L'\x7e')
+            {
+                const auto id = idBuilder.Finalize(ch);
+                switch (charsetSize)
+                {
+                case DispatchTypes::CharsetSize::Size94:
+                    _termOutput.AssignUserPreferenceCharset(id, false);
+                    break;
+                case DispatchTypes::CharsetSize::Size96:
+                    _termOutput.AssignUserPreferenceCharset(id, true);
+                    break;
+                }
+                return false;
             }
-            return false;
         }
         return true;
     };
@@ -3932,8 +3938,8 @@ ITermDispatch::StringHandler AdaptDispatch::DefineMacro(const VTInt macroId,
 
     if (_macroBuffer->InitParser(macroId, deleteControl, encoding))
     {
-        return [&](const auto ch) {
-            return _macroBuffer->ParseDefinition(ch);
+        return [&](const std::wstring_view str) {
+            return _macroBuffer->ParseDefinition(str);
         };
     }
 
@@ -4053,45 +4059,48 @@ void AdaptDispatch::_ReportColorTable(const DispatchTypes::ColorModel colorModel
 // - a function to parse the report data.
 ITermDispatch::StringHandler AdaptDispatch::_RestoreColorTable()
 {
-    return [this, parameter = VTInt{}, parameters = std::vector<VTParameter>{}](const auto ch) mutable {
-        if (ch >= L'0' && ch <= L'9')
+    return [this, parameter = VTInt{}, parameters = std::vector<VTParameter>{}](const std::wstring_view str) mutable {
+        for (const auto ch : str)
         {
-            parameter *= 10;
-            parameter += (ch - L'0');
-            parameter = std::min(parameter, MAX_PARAMETER_VALUE);
-        }
-        else if (ch == L';')
-        {
-            if (parameters.size() < 5)
+            if (ch >= L'0' && ch <= L'9')
+            {
+                parameter *= 10;
+                parameter += (ch - L'0');
+                parameter = std::min(parameter, MAX_PARAMETER_VALUE);
+            }
+            else if (ch == L';')
+            {
+                if (parameters.size() < 5)
+                {
+                    parameters.push_back(parameter);
+                }
+                parameter = 0;
+            }
+            else if (ch == L'/' || ch == AsciiChars::ESC)
             {
                 parameters.push_back(parameter);
-            }
-            parameter = 0;
-        }
-        else if (ch == L'/' || ch == AsciiChars::ESC)
-        {
-            parameters.push_back(parameter);
-            const auto colorParameters = VTParameters{ parameters.data(), parameters.size() };
-            const auto colorNumber = colorParameters.at(0).value_or(0);
-            if (colorNumber < TextColor::TABLE_SIZE)
-            {
-                const auto colorModel = DispatchTypes::ColorModel{ colorParameters.at(1) };
-                const auto x = colorParameters.at(2).value_or(0);
-                const auto y = colorParameters.at(3).value_or(0);
-                const auto z = colorParameters.at(4).value_or(0);
-                if (colorModel == DispatchTypes::ColorModel::HLS)
+                const auto colorParameters = VTParameters{ parameters.data(), parameters.size() };
+                const auto colorNumber = colorParameters.at(0).value_or(0);
+                if (colorNumber < TextColor::TABLE_SIZE)
                 {
-                    SetColorTableEntry(colorNumber, Utils::ColorFromHLS(x, y, z));
-                }
-                else if (colorModel == DispatchTypes::ColorModel::RGB)
-                {
-                    SetColorTableEntry(colorNumber, Utils::ColorFromRGB100(x, y, z));
+                    const auto colorModel = DispatchTypes::ColorModel{ colorParameters.at(1) };
+                    const auto x = colorParameters.at(2).value_or(0);
+                    const auto y = colorParameters.at(3).value_or(0);
+                    const auto z = colorParameters.at(4).value_or(0);
+                    if (colorModel == DispatchTypes::ColorModel::HLS)
+                    {
+                        SetColorTableEntry(colorNumber, Utils::ColorFromHLS(x, y, z));
+                    }
+                    else if (colorModel == DispatchTypes::ColorModel::RGB)
+                    {
+                        SetColorTableEntry(colorNumber, Utils::ColorFromRGB100(x, y, z));
+                    }
                 }
+                parameters.clear();
+                parameter = 0;
             }
-            parameters.clear();
-            parameter = 0;
         }
-        return (ch != AsciiChars::ESC);
+        return true;
     };
 }
 
@@ -4111,42 +4120,43 @@ ITermDispatch::StringHandler AdaptDispatch::RequestSetting()
     // this is the opposite of what is documented in most DEC manuals, which
     // say that 0 is for a valid response, and 1 is for an error. The correct
     // interpretation is documented in the DEC STD 070 reference.
-    return [this, parameter = VTInt{}, idBuilder = VTIDBuilder{}](const auto ch) mutable {
-        const auto isFinal = ch >= L'\x40' && ch <= L'\x7e';
-        if (isFinal)
+    return [this, parameter = VTInt{}, idBuilder = VTIDBuilder{}](const std::wstring_view str) mutable {
+        for (const auto ch : str)
         {
-            const auto id = idBuilder.Finalize(ch);
-            switch (id)
+            const auto isFinal = ch >= L'\x40' && ch <= L'\x7e';
+            if (isFinal)
             {
-            case VTID("m"):
-                _ReportSGRSetting();
-                break;
-            case VTID("r"):
-                _ReportDECSTBMSetting();
-                break;
-            case VTID("s"):
-                _ReportDECSLRMSetting();
-                break;
-            case VTID(" q"):
-                _ReportDECSCUSRSetting();
-                break;
-            case VTID("\"q"):
-                _ReportDECSCASetting();
-                break;
-            case VTID("*x"):
-                _ReportDECSACESetting();
-                break;
-            case VTID(",|"):
-                _ReportDECACSetting(VTParameter{ parameter });
-                break;
-            default:
-                _ReturnDcsResponse(L"0$r");
-                break;
+                const auto id = idBuilder.Finalize(ch);
+                switch (id)
+                {
+                case VTID("m"):
+                    _ReportSGRSetting();
+                    break;
+                case VTID("r"):
+                    _ReportDECSTBMSetting();
+                    break;
+                case VTID("s"):
+                    _ReportDECSLRMSetting();
+                    break;
+                case VTID(" q"):
+                    _ReportDECSCUSRSetting();
+                    break;
+                case VTID("\"q"):
+                    _ReportDECSCASetting();
+                    break;
+                case VTID("*x"):
+                    _ReportDECSACESetting();
+                    break;
+                case VTID(",|"):
+                    _ReportDECACSetting(VTParameter{ parameter });
+                    break;
+                default:
+                    _ReturnDcsResponse(L"0$r");
+                    break;
+                }
+                return false;
             }
-            return false;
-        }
-        else
-        {
+
             // Although we don't yet support any operations with parameter
             // prefixes, it's important that we still parse the prefix and
             // include it in the ID. Otherwise, we'll mistakenly respond to
@@ -4164,8 +4174,8 @@ ITermDispatch::StringHandler AdaptDispatch::RequestSetting()
                 parameter += (ch - L'0');
                 parameter = std::min(parameter, MAX_PARAMETER_VALUE);
             }
-            return true;
         }
+        return true;
     };
 }
 
@@ -4513,126 +4523,129 @@ ITermDispatch::StringHandler AdaptDispatch::_RestoreCursorInformation()
         VTParameter row{};
         VTParameter column{};
     };
-    return [&, state = State{}](const auto ch) mutable {
-        if (numeric.test(state.field))
+    return [&, state = State{}](const std::wstring_view str) mutable {
+        for (const auto ch : str)
         {
-            if (ch >= '0' && ch <= '9')
+            if (numeric.test(state.field))
             {
-                state.value *= 10;
-                state.value += (ch - L'0');
-                state.value = std::min(state.value, MAX_PARAMETER_VALUE);
+                if (ch >= '0' && ch <= '9')
+                {
+                    state.value *= 10;
+                    state.value += (ch - L'0');
+                    state.value = std::min(state.value, MAX_PARAMETER_VALUE);
+                }
+                else if (ch == L';' || ch == AsciiChars::ESC)
+                {
+                    if (state.field == Field::Row)
+                    {
+                        state.row = state.value;
+                    }
+                    else if (state.field == Field::Column)
+                    {
+                        state.column = state.value;
+                    }
+                    else if (state.field == Field::Page)
+                    {
+                        PagePositionAbsolute(state.value);
+                    }
+                    else if (state.field == Field::GL && state.value <= 3)
+                    {
+                        LockingShift(state.value);
+                    }
+                    else if (state.field == Field::GR && state.value <= 3)
+                    {
+                        LockingShiftRight(state.value);
+                    }
+                    state.value = {};
+                    state.field = static_cast<Field>(state.field + 1);
+                }
             }
-            else if (ch == L';' || ch == AsciiChars::ESC)
+            else if (flags.test(state.field))
             {
-                if (state.field == Field::Row)
+                // Note that there could potentially be multiple characters in a
+                // flag field, so we process the flags as soon as they're received.
+                // But for now we're only interested in the first one, so once the
+                // state.value is set, we ignore everything else until the `;`.
+                if (ch >= L'@' && ch <= '~' && !state.value)
                 {
-                    state.row = state.value;
-                }
-                else if (state.field == Field::Column)
-                {
-                    state.column = state.value;
-                }
-                else if (state.field == Field::Page)
-                {
-                    PagePositionAbsolute(state.value);
-                }
-                else if (state.field == Field::GL && state.value <= 3)
-                {
-                    LockingShift(state.value);
-                }
-                else if (state.field == Field::GR && state.value <= 3)
-                {
-                    LockingShiftRight(state.value);
-                }
-                state.value = {};
-                state.field = static_cast<Field>(state.field + 1);
-            }
-        }
-        else if (flags.test(state.field))
-        {
-            // Note that there could potentially be multiple characters in a
-            // flag field, so we process the flags as soon as they're received.
-            // But for now we're only interested in the first one, so once the
-            // state.value is set, we ignore everything else until the `;`.
-            if (ch >= L'@' && ch <= '~' && !state.value)
-            {
-                state.value = ch;
-                if (state.field == Field::SGR)
-                {
-                    const auto page = _pages.ActivePage();
-                    auto attr = page.Attributes();
-                    attr.SetIntense(state.value & 1);
-                    attr.SetUnderlineStyle(state.value & 2 ? UnderlineStyle::SinglyUnderlined : UnderlineStyle::NoUnderline);
-                    attr.SetBlinking(state.value & 4);
-                    attr.SetReverseVideo(state.value & 8);
-                    attr.SetInvisible(state.value & 16);
-                    page.SetAttributes(attr);
-                }
-                else if (state.field == Field::Attr)
-                {
-                    const auto page = _pages.ActivePage();
-                    auto attr = page.Attributes();
-                    attr.SetProtected(state.value & 1);
-                    page.SetAttributes(attr);
-                }
-                else if (state.field == Field::Sizes)
-                {
-                    state.charset96.at(0) = state.value & 1;
-                    state.charset96.at(1) = state.value & 2;
-                    state.charset96.at(2) = state.value & 4;
-                    state.charset96.at(3) = state.value & 8;
-                }
-                else if (state.field == Field::Flags)
-                {
-                    const bool originMode = state.value & 1;
-                    const bool ss2 = state.value & 2;
-                    const bool ss3 = state.value & 4;
-                    const bool delayedEOLWrap = state.value & 8;
-                    // The cursor position is parsed at the start of the sequence,
-                    // but we only set the position once we know the origin mode.
-                    _modes.set(Mode::Origin, originMode);
-                    CursorPosition(state.row, state.column);
-                    // There can only be one single shift applied at a time, so
-                    // we'll just apply the last one that is enabled.
-                    _termOutput.SingleShift(ss3 ? 3 : (ss2 ? 2 : 0));
-                    // The EOL flag will always be reset by the cursor movement
-                    // above, so we only need to worry about setting it.
-                    if (delayedEOLWrap)
+                    state.value = ch;
+                    if (state.field == Field::SGR)
                     {
                         const auto page = _pages.ActivePage();
-                        page.Cursor().DelayEOLWrap();
+                        auto attr = page.Attributes();
+                        attr.SetIntense(state.value & 1);
+                        attr.SetUnderlineStyle(state.value & 2 ? UnderlineStyle::SinglyUnderlined : UnderlineStyle::NoUnderline);
+                        attr.SetBlinking(state.value & 4);
+                        attr.SetReverseVideo(state.value & 8);
+                        attr.SetInvisible(state.value & 16);
+                        page.SetAttributes(attr);
+                    }
+                    else if (state.field == Field::Attr)
+                    {
+                        const auto page = _pages.ActivePage();
+                        auto attr = page.Attributes();
+                        attr.SetProtected(state.value & 1);
+                        page.SetAttributes(attr);
+                    }
+                    else if (state.field == Field::Sizes)
+                    {
+                        state.charset96.at(0) = state.value & 1;
+                        state.charset96.at(1) = state.value & 2;
+                        state.charset96.at(2) = state.value & 4;
+                        state.charset96.at(3) = state.value & 8;
+                    }
+                    else if (state.field == Field::Flags)
+                    {
+                        const bool originMode = state.value & 1;
+                        const bool ss2 = state.value & 2;
+                        const bool ss3 = state.value & 4;
+                        const bool delayedEOLWrap = state.value & 8;
+                        // The cursor position is parsed at the start of the sequence,
+                        // but we only set the position once we know the origin mode.
+                        _modes.set(Mode::Origin, originMode);
+                        CursorPosition(state.row, state.column);
+                        // There can only be one single shift applied at a time, so
+                        // we'll just apply the last one that is enabled.
+                        _termOutput.SingleShift(ss3 ? 3 : (ss2 ? 2 : 0));
+                        // The EOL flag will always be reset by the cursor movement
+                        // above, so we only need to worry about setting it.
+                        if (delayedEOLWrap)
+                        {
+                            const auto page = _pages.ActivePage();
+                            page.Cursor().DelayEOLWrap();
+                        }
                     }
                 }
+                else if (ch == L';')
+                {
+                    state.value = 0;
+                    state.field = static_cast<Field>(state.field + 1);
+                }
             }
-            else if (ch == L';')
+            else if (charset.test(state.field))
             {
-                state.value = 0;
-                state.field = static_cast<Field>(state.field + 1);
+                if (ch >= L' ' && ch <= L'/')
+                {
+                    state.charsetId.AddIntermediate(ch);
+                }
+                else if (ch >= L'0' && ch <= L'~')
+                {
+                    const auto id = state.charsetId.Finalize(ch);
+                    const auto gset = state.field - Field::G0;
+                    if (state.charset96.at(gset))
+                    {
+                        Designate96Charset(gset, id);
+                    }
+                    else
+                    {
+                        Designate94Charset(gset, id);
+                    }
+                    state.charsetId.Clear();
+                    state.field = static_cast<Field>(state.field + 1);
+                }
             }
         }
-        else if (charset.test(state.field))
-        {
-            if (ch >= L' ' && ch <= L'/')
-            {
-                state.charsetId.AddIntermediate(ch);
-            }
-            else if (ch >= L'0' && ch <= L'~')
-            {
-                const auto id = state.charsetId.Finalize(ch);
-                const auto gset = state.field - Field::G0;
-                if (state.charset96.at(gset))
-                {
-                    Designate96Charset(gset, id);
-                }
-                else
-                {
-                    Designate94Charset(gset, id);
-                }
-                state.charsetId.Clear();
-                state.field = static_cast<Field>(state.field + 1);
-            }
-        }
-        return (ch != AsciiChars::ESC);
+        return true;
     };
 }
 
@@ -4685,30 +4698,33 @@ ITermDispatch::StringHandler AdaptDispatch::_RestoreTabStops()
     _ClearAllTabStops();
     _InitTabStopsForWidth(width);
 
-    return [this, width, column = size_t{}](const auto ch) mutable {
-        if (ch >= L'0' && ch <= L'9')
+    return [this, width, column = size_t{}](const std::wstring_view str) mutable {
+        for (const auto ch : str)
         {
-            column *= 10;
-            column += (ch - L'0');
-            column = std::min<size_t>(column, MAX_PARAMETER_VALUE);
-        }
-        else if (ch == L'/' || ch == AsciiChars::ESC)
-        {
-            // Note that column 1 is always a tab stop, so there is no
-            // need to record an entry at that offset.
-            if (column > 1u && column <= static_cast<size_t>(width))
+            if (ch >= L'0' && ch <= L'9')
             {
-                _tabStopColumns.at(column - 1) = true;
+                column *= 10;
+                column += (ch - L'0');
+                column = std::min<size_t>(column, MAX_PARAMETER_VALUE);
+            }
+            else if (ch == L'/' || ch == AsciiChars::ESC)
+            {
+                // Note that column 1 is always a tab stop, so there is no
+                // need to record an entry at that offset.
+                if (column > 1u && column <= static_cast<size_t>(width))
+                {
+                    _tabStopColumns.at(column - 1) = true;
+                }
+                column = 0;
+            }
+            else
+            {
+                // If we receive an unexpected character, we don't try and
+                // process any more of the input - we just abort.
+                return false;
             }
-            column = 0;
         }
-        else
-        {
-            // If we receive an unexpected character, we don't try and
-            // process any more of the input - we just abort.
-            return false;
-        }
-        return (ch != AsciiChars::ESC);
+        return true;
     };
 }
 

src/terminal/adapter/ut_adapter/adapterTest.cpp

@@ -1847,11 +1847,8 @@ public:
     {
         const auto requestSetting = [=](const std::wstring_view settingId = {}) {
             const auto stringHandler = _pDispatch->RequestSetting();
-            for (auto ch : settingId)
-            {
-                stringHandler(ch);
-            }
-            stringHandler(L'\033'); // String terminator
+            stringHandler(settingId);
+            stringHandler(L"\033"); // String terminator
         };
 
         Log::Comment(L"Requesting DECSTBM margins (5 to 10).");
@@ -3568,11 +3565,8 @@ public:
     {
         const auto assignCharset = [=](const auto charsetSize, const std::wstring_view charsetId = {}) {
             const auto stringHandler = _pDispatch->AssignUserPreferenceCharset(charsetSize);
-            for (auto ch : charsetId)
-            {
-                stringHandler(ch);
-            }
-            stringHandler(L'\033'); // String terminator
+            stringHandler(charsetId);
+            stringHandler(L"\033"); // String terminator
         };
         auto& termOutput = _pDispatch->_termOutput;
         termOutput.SoftReset();

src/terminal/parser/IStateMachineEngine.hpp

@@ -20,7 +20,7 @@ namespace Microsoft::Console::VirtualTerminal
     class IStateMachineEngine
     {
     public:
-        using StringHandler = std::function<bool(const wchar_t)>;
+        using StringHandler = std::function<bool(std::wstring_view)>;
 
         virtual ~IStateMachineEngine() = 0;
         IStateMachineEngine(const IStateMachineEngine&) = default;

src/terminal/parser/stateMachine.cpp

@@ -13,17 +13,7 @@ using namespace Microsoft::Console::VirtualTerminal;
 //Takes ownership of the pEngine.
 StateMachine::StateMachine(std::unique_ptr<IStateMachineEngine> engine, const bool isEngineForInput) noexcept :
     _engine(std::move(engine)),
-    _isEngineForInput(isEngineForInput),
-    _state(VTStates::Ground),
-    _trace(Microsoft::Console::VirtualTerminal::ParserTracing()),
-    _parameters{},
-    _subParameters{},
-    _subParameterRanges{},
-    _parameterLimitOverflowed(false),
-    _subParameterLimitOverflowed(false),
-    _subParameterCounter(0),
-    _oscString{},
-    _cachedSequence{ std::nullopt }
+    _isEngineForInput(isEngineForInput)
 {
     // The state machine must always accept C1 controls for the input engine,
     // otherwise it won't work when the ConPTY terminal has S8C1T enabled.
@@ -324,18 +314,6 @@ static constexpr bool _isDcsIndicator(const wchar_t wch) noexcept
     return wch == L'P'; // 0x50
 }
 
-// Routine Description:
-// - Determines if a character is valid for a DCS pass through sequence.
-// Arguments:
-// - wch - Character to check.
-// Return Value:
-// - True if it is. False if it isn't.
-static constexpr bool _isDcsPassThroughValid(const wchar_t wch) noexcept
-{
-    // 0x20 - 0x7E
-    return wch >= AsciiChars::SPC && wch < AsciiChars::DEL;
-}
-
 // Routine Description:
 // - Determines if a character is "start of string" beginning
 //      indicator.
@@ -655,7 +633,7 @@ void StateMachine::_ActionInterrupt()
     if (_state == VTStates::DcsPassThrough)
     {
         // The ESC signals the end of the data string.
-        _dcsStringHandler(AsciiChars::ESC);
+        _dcsStringHandler(L"\x1b");
         _dcsStringHandler = nullptr;
     }
 }
@@ -1799,20 +1777,70 @@ void StateMachine::_EventDcsParam(const wchar_t wch)
 // - wch - Character that triggered the event
 // Return Value:
 // - <none>
-void StateMachine::_EventDcsPassThrough(const wchar_t wch)
+void StateMachine::_EventDcsPassThrough(const wchar_t)
 {
+    static constexpr auto isDcsIgnore = [](const wchar_t wch) {
+        return wch == AsciiChars::DEL;
+    };
+    static constexpr auto isDcsTerminator = [](const wchar_t wch) {
+        return wch == AsciiChars::CAN ||
+               wch == AsciiChars::SUB ||
+               wch == AsciiChars::ESC ||
+               (wch >= 0x80 && wch <= 0x9F);
+    };
+    static constexpr auto isDcsActionable = [](const wchar_t wch) {
+        return wch == AsciiChars::CAN ||
+               wch == AsciiChars::SUB ||
+               wch == AsciiChars::ESC ||
+               wch == AsciiChars::DEL ||
+               (wch >= 0x80 && wch <= 0x9F);
+    };
+
     _trace.TraceOnEvent(L"DcsPassThrough");
-    if (_isC0Code(wch) || _isDcsPassThroughValid(wch))
+
+    // Assuming other functions are correctly implemented,
+    // we're only called when we have data to process.
+    assert(_runEnd != 0 && _runEnd <= _currentString.size());
+
+    const auto end = _currentString.end();
+    auto runEnd = _currentString.begin() + (_runEnd - 1);
+
+    for (;;)
     {
-        if (!_dcsStringHandler(wch))
+        const auto runBeg = runEnd;
+
+        // Process a chunk of non-actionable, passthrough characters
+        // and exit if we're out of input.
+        for (; runEnd != end && !isDcsActionable(*runEnd); ++runEnd)
+        {
+        }
+        if (runBeg != runEnd && !_dcsStringHandler({ runBeg, runEnd }))
         {
             _EnterDcsIgnore();
+            break;
+        }
+        if (runEnd == end)
+        {
+            break;
+        }
+
+        // Ignore DEL characters.
+        for (; runEnd != end && isDcsIgnore(*runEnd); ++runEnd)
+        {
+        }
+        if (runEnd == end)
+        {
+            break;
+        }
+
+        // Are we looking at a terminator?
+        if (isDcsTerminator(*runEnd))
+        {
+            break;
         }
     }
-    else
-    {
-        _ActionIgnore();
-    }
+
+    _runEnd = runEnd - _currentString.begin();
 }
 
 // Routine Description:
@@ -1973,144 +2001,169 @@ bool StateMachine::FlushToTerminal()
 // - string - Characters to operate upon
 // Return Value:
 // - <none>
+#pragma warning(suppress : 26438) // Avoid 'goto'(es .76).
+#pragma warning(suppress : 26481) // Don't use pointer arithmetic. Use span instead (bounds.1).)
 void StateMachine::ProcessString(const std::wstring_view string)
 {
-    size_t i = 0;
     _currentString = string;
-    _runOffset = 0;
-    _runSize = 0;
+    _runBeg = 0;
+    _runEnd = 0;
     _injections.clear();
 
     if (_state != VTStates::Ground)
     {
         // Jump straight to where we need to.
-#pragma warning(suppress : 26438) // Avoid 'goto'(es .76).
+#pragma warning(suppress : 26438) // Avoid 'goto' (es.76).
         goto processStringLoopVtStart;
     }
 
-    while (i < string.size())
+    for (;;)
     {
+        // Process as much plain text as possible.
         {
-            // Pointer arithmetic is perfectly fine for our hot path.
-#pragma warning(suppress : 26481) // Don't use pointer arithmetic. Use span instead (bounds.1).)
-            const auto beg = string.data() + i;
-            const auto len = string.size() - i;
+            // We're starting a new "chunk".
+            // --> Reset beg(in).
+            _runBeg = _runEnd;
+
+            // Ran out of text. Return.
+            if (_runBeg >= _currentString.size())
+            {
+                return;
+            }
+
+#pragma warning(suppress : 26481) // Don't use pointer arithmetic. Use span instead (bounds.1).
+            const auto beg = _currentString.data() + _runBeg;
+            const auto len = _currentString.size() - _runBeg;
             const auto it = Microsoft::Console::Utils::FindActionableControlCharacter(beg, len);
 
-            _runOffset = i;
-            _runSize = it - beg;
-
-            if (_runSize)
+            if (it != beg)
             {
+                _runEnd = it - _currentString.data();
                 _ActionPrintString(_CurrentRun());
-
-                i += _runSize;
-                _runOffset = i;
-                _runSize = 0;
+                _runBeg = _runEnd;
             }
         }
 
+        // Next, process VT sequences (plural!).
     processStringLoopVtStart:
-        if (i >= string.size())
+        // Ran out of text. Return.
+        if (_runBeg >= _currentString.size())
         {
-            break;
+            return;
         }
-
-        do
+        for (;;)
         {
-            _runSize++;
-            _processingLastCharacter = i + 1 >= string.size();
-            // If we're processing characters individually, send it to the state machine.
-            ProcessCharacter(til::at(string, i));
-            ++i;
-        } while (i < string.size() && _state != VTStates::Ground);
-    }
-
-    // If we're at the end of the string and have remaining un-printed characters,
-    if (_state != VTStates::Ground)
-    {
-        const auto run = _CurrentRun();
-        auto cacheUnusedRun = true;
-
-        // One of the "weird things" in VT input is the case of something like
-        // <kbd>alt+[</kbd>. In VT, that's encoded as `\x1b[`. However, that's
-        // also the start of a CSI, and could be the start of a longer sequence,
-        // there's no way to know for sure. For an <kbd>alt+[</kbd> keypress,
-        // the parser originally would just sit in the `CsiEntry` state after
-        // processing it, which would pollute the following keypress (e.g.
-        // <kbd>alt+[</kbd>, <kbd>A</kbd> would be processed like `\x1b[A`,
-        // which is _wrong_).
-        //
-        // At the same time, input may be broken up arbitrarily, depending on the pipe's
-        // buffer size, our read-buffer size, the sender's write-buffer size, and more.
-        // In fact, with the current WSL, input is broken up in 16 byte chunks (Why? :(),
-        // which breaks up many of our longer sequences, like our Win32InputMode ones.
-        //
-        // As a heuristic, this code specifically checks for a trailing Esc or Alt+key.
-        // If we encountered a win32-input-mode sequence before, we know that our \x1b[?9001h
-        // request to enable them was successful. While a client may still send \x1b{some char}
-        // intentionally, it's far more likely now that we're looking at a broken up sequence.
-        // The most common win32-input-mode is ConPTY itself after all, and we never emit
-        // \x1b{some char} once it's enabled.
-        if (_isEngineForInput)
-        {
-            const auto win32 = _engine->EncounteredWin32InputModeSequence();
-            if (!win32 && run.size() <= 2 && run.front() == L'\x1b')
+            // The inner loop deals with 1 VT sequence at a time.
+            for (;;)
             {
-                _EnterGround();
-                if (run.size() == 1)
-                {
-                    _ActionExecute(L'\x1b');
-                }
-                else
-                {
-                    _EnterEscape();
-                    _ActionEscDispatch(run.back());
-                }
-                _EnterGround();
-                // No need to cache the run, since we've dealt with it now.
-                cacheUnusedRun = false;
-            }
-        }
-        else if (_state == VTStates::SosPmApcString || _state == VTStates::DcsPassThrough || _state == VTStates::DcsIgnore)
-        {
-            // There is no need to cache the run if we've reached one of the
-            // string processing states in the output engine, since that data
-            // will be dealt with as soon as it is received.
-            cacheUnusedRun = false;
-        }
+                const auto ch = til::at(_currentString, _runEnd);
+                ++_runEnd;
+                ProcessCharacter(ch);
 
-        // If the run hasn't been dealt with in one of the cases above, we cache
-        // the partial sequence in case we have to flush the whole thing later.
-        if (cacheUnusedRun)
-        {
-            if (!_cachedSequence)
-            {
-                _cachedSequence.emplace(std::wstring{});
+                if (_state == VTStates::Ground)
+                {
+                    break;
+                }
+
+                // We're not back in ground state, but ran out of text.
+                // --> Incomplete sequence. Clean up at the end.
+                if (_runEnd >= _currentString.size())
+                {
+                    _processStringIncompleteSequence();
+                    return;
+                }
             }
 
-            auto& cachedSequence = *_cachedSequence;
-            cachedSequence.append(run);
+            // The only way we get here is if the above loop ran into the ground state.
+            // This means we're starting a new "chunk".
+            // --> Reset beg(in).
+            _runBeg = _runEnd;
+
+            // Ran out of text. Return.
+            if (_runBeg >= _currentString.size())
+            {
+                return;
+            }
+
+            // Plain text? Go back to the start, where we process plain text.
+            if (!Utils::IsActionableFromGround(til::at(_currentString, _runEnd)))
+            {
+                break;
+            }
         }
     }
 }
 
-// Routine Description:
-// - Determines whether the character being processed is the last in the
-//   current output fragment, or there are more still to come. Other parts
-//   of the framework can use this information to work more efficiently.
-// Arguments:
-// - <none>
-// Return Value:
-// - True if we're processing the last character. False if not.
-bool StateMachine::IsProcessingLastCharacter() const noexcept
+void Microsoft::Console::VirtualTerminal::StateMachine::_processStringIncompleteSequence()
 {
-    return _processingLastCharacter;
+    const auto run = _CurrentRun();
+    auto cacheUnusedRun = true;
+
+    // One of the "weird things" in VT input is the case of something like
+    // <kbd>alt+[</kbd>. In VT, that's encoded as `\x1b[`. However, that's
+    // also the start of a CSI, and could be the start of a longer sequence,
+    // there's no way to know for sure. For an <kbd>alt+[</kbd> keypress,
+    // the parser originally would just sit in the `CsiEntry` state after
+    // processing it, which would pollute the following keypress (e.g.
+    // <kbd>alt+[</kbd>, <kbd>A</kbd> would be processed like `\x1b[A`,
+    // which is _wrong_).
+    //
+    // At the same time, input may be broken up arbitrarily, depending on the pipe's
+    // buffer size, our read-buffer size, the sender's write-buffer size, and more.
+    // In fact, with the current WSL, input is broken up in 16 byte chunks (Why? :(),
+    // which breaks up many of our longer sequences, like our Win32InputMode ones.
+    //
+    // As a heuristic, this code specifically checks for a trailing Esc or Alt+key.
+    // If we encountered a win32-input-mode sequence before, we know that our \x1b[?9001h
+    // request to enable them was successful. While a client may still send \x1b{some char}
+    // intentionally, it's far more likely now that we're looking at a broken up sequence.
+    // The most common win32-input-mode is ConPTY itself after all, and we never emit
+    // \x1b{some char} once it's enabled.
+    if (_isEngineForInput)
+    {
+        const auto win32 = _engine->EncounteredWin32InputModeSequence();
+        if (!win32 && run.size() <= 2 && run.front() == L'\x1b')
+        {
+            _EnterGround();
+            if (run.size() == 1)
+            {
+                _ActionExecute(L'\x1b');
+            }
+            else
+            {
+                _EnterEscape();
+                _ActionEscDispatch(run.back());
+            }
+            _EnterGround();
+            // No need to cache the run, since we've dealt with it now.
+            cacheUnusedRun = false;
+        }
+    }
+    else if (_state == VTStates::SosPmApcString || _state == VTStates::DcsPassThrough || _state == VTStates::DcsIgnore)
+    {
+        // There is no need to cache the run if we've reached one of the
+        // string processing states in the output engine, since that data
+        // will be dealt with as soon as it is received.
+        cacheUnusedRun = false;
+    }
+
+    // If the run hasn't been dealt with in one of the cases above, we cache
+    // the partial sequence in case we have to flush the whole thing later.
+    if (cacheUnusedRun)
+    {
+        if (!_cachedSequence)
+        {
+            _cachedSequence.emplace(std::wstring{});
+        }
+
+        auto& cachedSequence = *_cachedSequence;
+        cachedSequence.append(run);
+    }
 }
 
 void StateMachine::InjectSequence(const InjectionType type)
 {
-    _injections.emplace_back(type, _runOffset + _runSize);
+    _injections.emplace_back(type, _runEnd);
 }
 
 const til::small_vector<Injection, 8>& StateMachine::GetInjections() const noexcept
@@ -2191,8 +2244,8 @@ void StateMachine::_ExecuteCsiCompleteCallback()
         // We need to save the state of the string that we're currently
         // processing in case the callback injects another string.
         const auto savedCurrentString = _currentString;
-        const auto savedRunOffset = _runOffset;
-        const auto savedRunSize = _runSize;
+        const auto savedRunBeg = _runBeg;
+        const auto savedRunEnd = _runEnd;
         // We also need to take ownership of the callback function before
         // executing it so there's no risk of it being run more than once.
         const auto callback = std::move(_onCsiCompleteCallback);
@@ -2200,7 +2253,16 @@ void StateMachine::_ExecuteCsiCompleteCallback()
         // Once the callback has returned, we can restore the original state
         // and continue where we left off.
         _currentString = savedCurrentString;
-        _runOffset = savedRunOffset;
-        _runSize = savedRunSize;
+        _runBeg = savedRunBeg;
+        _runEnd = savedRunEnd;
     }
 }
+
+// Construct current run.
+//
+// Note: We intentionally use this method to create the run lazily for better performance.
+//       You may find the usage of offset & size unsafe, but under heavy load it shows noticeable performance benefit.
+std::wstring_view Microsoft::Console::VirtualTerminal::StateMachine::_CurrentRun() const
+{
+    return _currentString.substr(_runBeg, _runEnd - _runBeg);
+}

src/terminal/parser/stateMachine.hpp

@@ -81,7 +81,6 @@ namespace Microsoft::Console::VirtualTerminal
 
         void ProcessCharacter(const wchar_t wch);
         void ProcessString(const std::wstring_view string);
-        bool IsProcessingLastCharacter() const noexcept;
 
         void InjectSequence(InjectionType type);
         const til::small_vector<Injection, 8>& GetInjections() const noexcept;
@@ -94,6 +93,8 @@ namespace Microsoft::Console::VirtualTerminal
         IStateMachineEngine& Engine() noexcept;
 
     private:
+        void _processStringIncompleteSequence();
+
         void _ActionExecute(const wchar_t wch);
         void _ActionExecuteFromEscape(const wchar_t wch);
         void _ActionPrint(const wchar_t wch);
@@ -162,6 +163,7 @@ namespace Microsoft::Console::VirtualTerminal
         bool _SafeExecute(TLambda&& lambda);
 
         void _ExecuteCsiCompleteCallback();
+        std::wstring_view _CurrentRun() const;
 
         enum class VTStates
         {
@@ -192,43 +194,30 @@ namespace Microsoft::Console::VirtualTerminal
         std::unique_ptr<IStateMachineEngine> _engine;
         const bool _isEngineForInput;
 
-        VTStates _state;
+        VTStates _state = VTStates::Ground;
 
         til::enumset<Mode> _parserMode{ Mode::Ansi };
 
         std::wstring_view _currentString;
-        size_t _runOffset;
-        size_t _runSize;
-
-        // Construct current run.
-        //
-        // Note: We intentionally use this method to create the run lazily for better performance.
-        //       You may find the usage of offset & size unsafe, but under heavy load it shows noticeable performance benefit.
-        std::wstring_view _CurrentRun() const
-        {
-            return _currentString.substr(_runOffset, _runSize);
-        }
+        size_t _runBeg = 0;
+        size_t _runEnd = 0;
 
         VTIDBuilder _identifier;
         std::vector<VTParameter> _parameters;
-        bool _parameterLimitOverflowed;
         std::vector<VTParameter> _subParameters;
         std::vector<std::pair<BYTE /*range start*/, BYTE /*range end*/>> _subParameterRanges;
-        bool _subParameterLimitOverflowed;
-        BYTE _subParameterCounter;
+        bool _parameterLimitOverflowed = false;
+        bool _subParameterLimitOverflowed = false;
+        BYTE _subParameterCounter = 0;
 
         std::wstring _oscString;
-        VTInt _oscParameter;
+        VTInt _oscParameter = 0;
 
         IStateMachineEngine::StringHandler _dcsStringHandler;
 
         std::optional<std::wstring> _cachedSequence;
         til::small_vector<Injection, 8> _injections;
 
-        // This is tracked per state machine instance so that separate calls to Process*
-        //   can start and finish a sequence.
-        bool _processingLastCharacter;
-
         std::function<void()> _onCsiCompleteCallback;
     };
 }

src/types/inc/utils.hpp

@@ -126,6 +126,7 @@ namespace Microsoft::Console::Utils
     // testing easier.
     std::wstring_view TrimPaste(std::wstring_view textView) noexcept;
 
+    bool IsActionableFromGround(const wchar_t wch) noexcept;
     const wchar_t* FindActionableControlCharacter(const wchar_t* beg, const size_t len) noexcept;
 
     // Same deal, but in TerminalPage::_evaluatePathForCwd

src/types/utils.cpp

@@ -1139,7 +1139,8 @@ std::wstring_view Utils::TrimPaste(std::wstring_view textView) noexcept
 #pragma warning(disable : 26490) // Don't use reinterpret_cast (type.1).
 
 // Returns true for C0 characters and C1 [single-character] CSI.
-constexpr bool isActionableFromGround(const wchar_t wch) noexcept
+#pragma warning(suppress : 26497) // You can attempt to make 'Microsoft::Console::Utils::IsActionableFromGround' constexpr unless it contains any undefined behavior(f.4).
+bool Utils::IsActionableFromGround(const wchar_t wch) noexcept
 {
     // This is equivalent to:
     //   return (wch <= 0x1f) || (wch >= 0x7f && wch <= 0x9f);
@@ -1230,7 +1231,7 @@ plainSearch:
 #endif
 
 #pragma loop(no_vector)
-    for (const auto end = beg + len; it < end && !isActionableFromGround(*it); ++it)
+    for (const auto end = beg + len; it < end && !IsActionableFromGround(*it); ++it)
     {
     }