Filter focus events that came from the API

.github/actions/spelling/allow/allow.txt

@@ -44,6 +44,7 @@ inlined
 It'd
 kje
 libfuzzer
+libuv
 liga
 lje
 Llast

src/terminal/input/terminalInput.cpp

@@ -527,6 +527,14 @@ bool TerminalInput::HandleKey(const IInputEvent* const pInEvent)
     if (pInEvent->EventType() == InputEventType::FocusEvent)
     {
         const auto& focusEvent = *static_cast<const FocusEvent* const>(pInEvent);
+
+        // BODGY
+        // GH#13238 - Filter out focus events that came from the API.
+        if (focusEvent.CameFromApi())
+        {
+            return true;
+        }
+
         return HandleFocus(focusEvent.GetFocus());
     }
 

src/types/FocusEvent.cpp

@@ -1,5 +1,18 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
+//
+// BODGY: GH#13238
+//
+// It appears that some applications (libuv) like to send a FOCUS_EVENT_RECORD
+// as a way to jiggle the input handle. Focus events really shouldn't ever be
+// sent via the API, they don't really do anything internally. However, focus
+// events in the input buffer do get translated by the TerminalInput to VT
+// sequences if we're in the right input mode.
+//
+// To not prevent libuv from jiggling the handle with a focus event, and also
+// make sure that we don't erroneously translate that to a sequence of
+// characters, we're going to filter out focus events that came from the API
+// when translating to VT.
 
 #include "precomp.h"
 #include "inc/IInputEvent.hpp"

src/types/inc/IInputEvent.hpp

@@ -514,12 +514,14 @@ class FocusEvent : public IInputEvent
 {
 public:
     constexpr FocusEvent(const FOCUS_EVENT_RECORD& record) :
-        _focus{ !!record.bSetFocus }
+        _focus{ !!record.bSetFocus },
+        _cameFromApi{ true }
     {
     }
 
     constexpr FocusEvent(const bool focus) :
-        _focus{ focus }
+        _focus{ focus },
+        _cameFromApi{ false }
     {
     }
 
@@ -539,8 +541,15 @@ class FocusEvent : public IInputEvent
 
     void SetFocus(const bool focus) noexcept;
 
+    // BODGY - see FocusEvent.cpp for details.
+    constexpr bool CameFromApi() const noexcept
+    {
+        return _cameFromApi;
+    }
+
 private:
     bool _focus;
+    const bool _cameFromApi;
 
 #ifdef UNIT_TESTING
     friend std::wostream& operator<<(std::wostream& stream, const FocusEvent* const pFocusEvent);