Fix parsing of chunked win32-input-mode sequences

src/terminal/parser/IStateMachineEngine.hpp

@@ -28,6 +28,8 @@ namespace Microsoft::Console::VirtualTerminal
         IStateMachineEngine& operator=(const IStateMachineEngine&) = default;
         IStateMachineEngine& operator=(IStateMachineEngine&&) = default;
 
+        virtual bool EncounteredWin32InputModeSequence() const noexcept = 0;
+
         virtual bool ActionExecute(const wchar_t wch) = 0;
         virtual bool ActionExecuteFromEscape(const wchar_t wch) = 0;
         virtual bool ActionPrint(const wchar_t wch) = 0;

src/terminal/parser/InputStateMachineEngine.cpp

@@ -102,6 +102,11 @@ InputStateMachineEngine::InputStateMachineEngine(std::unique_ptr<IInteractDispat
     THROW_HR_IF_NULL(E_INVALIDARG, _pDispatch.get());
 }
 
+bool InputStateMachineEngine::EncounteredWin32InputModeSequence() const noexcept
+{
+    return _encounteredWin32InputModeSequence;
+}
+
 void InputStateMachineEngine::SetLookingForDSR(const bool looking) noexcept
 {
     _lookingForDSR = looking;
@@ -448,6 +453,7 @@ bool InputStateMachineEngine::ActionCsiDispatch(const VTID id, const VTParameter
         // Ctrl+C, Ctrl+Break are handled correctly.
         const auto key = _GenerateWin32Key(parameters);
         success = _pDispatch->WriteCtrlKey(key);
+        _encounteredWin32InputModeSequence = true;
         break;
     }
     default:

src/terminal/parser/InputStateMachineEngine.hpp

@@ -132,6 +132,7 @@ namespace Microsoft::Console::VirtualTerminal
         InputStateMachineEngine(std::unique_ptr<IInteractDispatch> pDispatch,
                                 const bool lookingForDSR);
 
+        bool EncounteredWin32InputModeSequence() const noexcept override;
         void SetLookingForDSR(const bool looking) noexcept;
 
         bool ActionExecute(const wchar_t wch) override;
@@ -167,6 +168,7 @@ namespace Microsoft::Console::VirtualTerminal
         const std::unique_ptr<IInteractDispatch> _pDispatch;
         std::function<bool()> _pfnFlushToInputQueue;
         bool _lookingForDSR;
+        bool _encounteredWin32InputModeSequence = false;
         DWORD _mouseButtonState = 0;
         std::chrono::milliseconds _doubleClickTime;
         std::optional<til::point> _lastMouseClickPos{};

src/terminal/parser/OutputStateMachineEngine.cpp

@@ -23,6 +23,11 @@ OutputStateMachineEngine::OutputStateMachineEngine(std::unique_ptr<ITermDispatch
     THROW_HR_IF_NULL(E_INVALIDARG, _dispatch.get());
 }
 
+bool OutputStateMachineEngine::EncounteredWin32InputModeSequence() const noexcept
+{
+    return false;
+}
+
 const ITermDispatch& OutputStateMachineEngine::Dispatch() const noexcept
 {
     return *_dispatch;

src/terminal/parser/OutputStateMachineEngine.hpp

@@ -29,6 +29,8 @@ namespace Microsoft::Console::VirtualTerminal
 
         OutputStateMachineEngine(std::unique_ptr<ITermDispatch> pDispatch);
 
+        bool EncounteredWin32InputModeSequence() const noexcept override;
+
         bool ActionExecute(const wchar_t wch) override;
         bool ActionExecuteFromEscape(const wchar_t wch) override;
 

src/terminal/parser/stateMachine.cpp

@@ -2144,9 +2144,15 @@ void StateMachine::ProcessString(const std::wstring_view string)
         // 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)
         {
-            if (run.size() <= 2 && run.front() == L'\x1b')
+            const auto win32 = _engine->EncounteredWin32InputModeSequence();
+            if (!win32 && run.size() <= 2 && run.front() == L'\x1b')
             {
                 _EnterGround();
                 if (run.size() == 1)

src/terminal/parser/ut_parser/StateMachineTest.cpp

@@ -40,6 +40,11 @@ class Microsoft::Console::VirtualTerminal::TestStateMachineEngine : public IStat
         dcsDataString.clear();
     }
 
+    bool EncounteredWin32InputModeSequence() const noexcept override
+    {
+        return false;
+    }
+
     bool ActionExecute(const wchar_t wch) override
     {
         executed += wch;