From ec24517a97a473ada508c47566fcf1f47257da2b Mon Sep 17 00:00:00 2001
From: James Holderness <j4_james@hotmail.com>
Date: Sat, 27 Apr 2024 18:38:32 +0100
Subject: [PATCH] Fix DECTCEM reset position in conpty stream.

---
 src/renderer/vt/XtermEngine.cpp | 3 ++-
 src/renderer/vt/state.cpp       | 1 +
 src/renderer/vt/vtrenderer.hpp  | 1 +
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/renderer/vt/XtermEngine.cpp b/src/renderer/vt/XtermEngine.cpp
index 14822351585..75fc3510fa6 100644
--- a/src/renderer/vt/XtermEngine.cpp
+++ b/src/renderer/vt/XtermEngine.cpp
@@ -45,6 +45,7 @@ XtermEngine::XtermEngine(_In_ wil::unique_hfile hPipe,
     // visible, then PaintCursor will be called, and we'll set this to true
     // during the frame.
     _nextCursorIsVisible = false;
+    _startOfFrameBufferIndex = _buffer.size();
 
     // Do not perform synchronization clearing in passthrough mode.
     // In passthrough, the terminal leads and we follow what it is
@@ -112,7 +113,7 @@ XtermEngine::XtermEngine(_In_ wil::unique_hfile hPipe,
         // by prepending a cursor off.
         if (_lastCursorIsVisible != Tribool::False)
         {
-            _buffer.insert(0, "\x1b[?25l");
+            _buffer.insert(_startOfFrameBufferIndex, "\x1b[?25l");
             _lastCursorIsVisible = Tribool::False;
         }
         // If the cursor was NOT previously visible, then that's fine! we don't
diff --git a/src/renderer/vt/state.cpp b/src/renderer/vt/state.cpp
index ea176e42f37..881fb0c2cce 100644
--- a/src/renderer/vt/state.cpp
+++ b/src/renderer/vt/state.cpp
@@ -158,6 +158,7 @@ void VtEngine::_flushImpl() noexcept
     {
         const auto fSuccess = WriteFile(_hFile.get(), _buffer.data(), gsl::narrow_cast<DWORD>(_buffer.size()), nullptr, nullptr);
         _buffer.clear();
+        _startOfFrameBufferIndex = 0;
         if (!fSuccess)
         {
             LOG_LAST_ERROR();
diff --git a/src/renderer/vt/vtrenderer.hpp b/src/renderer/vt/vtrenderer.hpp
index 0135e791169..0125fe17369 100644
--- a/src/renderer/vt/vtrenderer.hpp
+++ b/src/renderer/vt/vtrenderer.hpp
@@ -93,6 +93,7 @@ namespace Microsoft::Console::Render
     protected:
         wil::unique_hfile _hFile;
         std::string _buffer;
+        size_t _startOfFrameBufferIndex = 0;
 
         std::string _formatBuffer;
         std::string _conversionBuffer;