Improve reliability of VT responses

src/cascadia/TerminalControl/ControlCore.cpp

@@ -98,7 +98,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         Connection(connection);
 
         _terminal->SetWriteInputCallback([this](std::wstring_view wstr) {
-            _sendInputToConnection(wstr);
+            _pendingResponses.append(wstr);
         });
 
         // GH#8969: pre-seed working directory to prevent potential races
@@ -419,6 +419,20 @@ namespace winrt::Microsoft::Terminal::Control::implementation
     // Return Value:
     // - <none>
     void ControlCore::_sendInputToConnection(std::wstring_view wstr)
+    {
+        if (!wstr.empty())
+        {
+            _connection.WriteInput(winrt_wstring_to_array_view(wstr));
+        }
+    }
+
+    // Method Description:
+    // - Writes the given sequence as input to the active terminal connection,
+    // Arguments:
+    // - wstr: the string of characters to write to the terminal connection.
+    // Return Value:
+    // - <none>
+    void ControlCore::SendInput(const std::wstring_view wstr)
     {
         if (wstr.empty())
         {
@@ -435,21 +449,10 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         }
         else
         {
-            _connection.WriteInput(winrt_wstring_to_array_view(wstr));
+            _sendInputToConnection(wstr);
         }
     }
 
-    // Method Description:
-    // - Writes the given sequence as input to the active terminal connection,
-    // Arguments:
-    // - wstr: the string of characters to write to the terminal connection.
-    // Return Value:
-    // - <none>
-    void ControlCore::SendInput(const std::wstring_view wstr)
-    {
-        _sendInputToConnection(wstr);
-    }
-
     bool ControlCore::SendCharEvent(const wchar_t ch,
                                     const WORD scanCode,
                                     const ::Microsoft::Terminal::Core::ControlKeyStates modifiers)
@@ -485,7 +488,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         }
         if (out)
         {
-            _sendInputToConnection(*out);
+            SendInput(*out);
             return true;
         }
         return false;
@@ -643,7 +646,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         }
         if (out)
         {
-            _sendInputToConnection(*out);
+            SendInput(*out);
             return true;
         }
         return false;
@@ -662,7 +665,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         }
         if (out)
         {
-            _sendInputToConnection(*out);
+            SendInput(*out);
             return true;
         }
         return false;
@@ -1412,7 +1415,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         }
 
         // It's important to not hold the terminal lock while calling this function as sending the data may take a long time.
-        _sendInputToConnection(filtered);
+        SendInput(filtered);
 
         const auto lock = _terminal->LockForWriting();
         _terminal->ClearSelection();
@@ -2107,7 +2110,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
                     // Sending input requires that we're unlocked, because
                     // writing the input pipe may block indefinitely.
                     const auto suspension = _terminal->SuspendLock();
-                    _sendInputToConnection(buffer);
+                    SendInput(buffer);
                 }
             }
         }
@@ -2164,6 +2167,12 @@ namespace winrt::Microsoft::Terminal::Control::implementation
                 _terminal->Write(hstr);
             }
 
+            if (!_pendingResponses.empty())
+            {
+                _sendInputToConnection(_pendingResponses);
+                _pendingResponses.clear();
+            }
+
             // Start the throttled update of where our hyperlinks are.
             const auto shared = _shared.lock_shared();
             if (shared->outputIdle)
@@ -2480,9 +2489,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         }
         if (out && !out->empty())
         {
-            // _sendInputToConnection() asserts that we aren't in focus mode,
-            // but window focus events are always fine to send.
-            _connection.WriteInput(winrt_wstring_to_array_view(*out));
+            _sendInputToConnection(*out);
         }
     }
 

src/cascadia/TerminalControl/ControlCore.h

@@ -319,6 +319,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         winrt::com_ptr<ControlSettings> _settings{ nullptr };
 
         std::shared_ptr<::Microsoft::Terminal::Core::Terminal> _terminal{ nullptr };
+        std::wstring _pendingResponses;
 
         // NOTE: _renderEngine must be ordered before _renderer.
         //

src/cascadia/TerminalCore/TerminalApi.cpp

@@ -24,7 +24,6 @@ void Terminal::ReturnResponse(const std::wstring_view response)
 {
     if (_pfnWriteInput && !response.empty())
     {
-        const auto suspension = _readWriteLock.suspend();
         _pfnWriteInput(response);
     }
 }