From 63b6bba433d49f0c8ec523a7e552c4ebc01236bb Mon Sep 17 00:00:00 2001
From: Leonard Hecker <lhecker@microsoft.com>
Date: Fri, 17 Apr 2026 20:32:18 +0200
Subject: [PATCH] Fixed SetTerminalInputKeyboardLayout

---
 .github/actions/spelling/expect/expect.txt         |  1 -
 src/terminal/adapter/ut_adapter/TestHook.cpp       | 14 ++++++++++++++
 src/terminal/adapter/ut_adapter/TestHook.h         |  1 +
 src/terminal/adapter/ut_adapter/inputTest.cpp      |  8 ++------
 .../adapter/ut_adapter/kittyKeyboardProtocol.cpp   |  7 ++-----
 5 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/.github/actions/spelling/expect/expect.txt b/.github/actions/spelling/expect/expect.txt
index b82142391b..f6ebb617f1 100644
--- a/.github/actions/spelling/expect/expect.txt
+++ b/.github/actions/spelling/expect/expect.txt
@@ -28,7 +28,6 @@ ALIGNRIGHT
 allocing
 alpc
 ALTERNATENAME
-alternatename
 ALTF
 ALTGR
 ALTNUMPAD
diff --git a/src/terminal/adapter/ut_adapter/TestHook.cpp b/src/terminal/adapter/ut_adapter/TestHook.cpp
index 2b6759a89e..50f6fe1956 100644
--- a/src/terminal/adapter/ut_adapter/TestHook.cpp
+++ b/src/terminal/adapter/ut_adapter/TestHook.cpp
@@ -94,6 +94,11 @@ LayoutGuard& LayoutGuard::operator=(LayoutGuard&& other) noexcept
     return *this;
 }
 
+LayoutGuard::operator bool() const noexcept
+{
+    return _layout != nullptr;
+}
+
 LayoutGuard::operator HKL() const noexcept
 {
     return _layout;
@@ -103,6 +108,15 @@ LayoutGuard TestHook::SetTerminalInputKeyboardLayout(const wchar_t* klid)
 {
     THROW_HR_IF_MSG(E_UNEXPECTED, g_keyboardLayout != nullptr, "Nested layout test overrides are not supported");
 
+    // Check if the layout is installed. LoadKeyboardLayoutW silently returns the
+    // current active layout if the requested one is missing.
+    const auto keyPath = fmt::format(FMT_COMPILE(L"SYSTEM\\CurrentControlSet\\Control\\Keyboard Layouts\\{}"), klid);
+    wil::unique_hkey key;
+    if (RegOpenKeyExW(HKEY_LOCAL_MACHINE, keyPath.c_str(), 0, KEY_READ, key.addressof()) != ERROR_SUCCESS)
+    {
+        return {};
+    }
+
     const auto layout = LoadKeyboardLayoutW(klid, KLF_NOTELLSHELL);
     THROW_LAST_ERROR_IF_NULL(layout);
 
diff --git a/src/terminal/adapter/ut_adapter/TestHook.h b/src/terminal/adapter/ut_adapter/TestHook.h
index ffecb97584..f7e14e25a3 100644
--- a/src/terminal/adapter/ut_adapter/TestHook.h
+++ b/src/terminal/adapter/ut_adapter/TestHook.h
@@ -13,6 +13,7 @@ namespace TestHook
         LayoutGuard(LayoutGuard&& other) noexcept;
         LayoutGuard& operator=(LayoutGuard&& other) noexcept;
 
+        explicit operator bool() const noexcept;
         operator HKL() const noexcept;
 
     private:
diff --git a/src/terminal/adapter/ut_adapter/inputTest.cpp b/src/terminal/adapter/ut_adapter/inputTest.cpp
index 2967a695d1..cb221906bf 100644
--- a/src/terminal/adapter/ut_adapter/inputTest.cpp
+++ b/src/terminal/adapter/ut_adapter/inputTest.cpp
@@ -628,12 +628,8 @@ void InputTest::TerminalInputNullKeyTests()
 {
     using namespace std::string_view_literals;
 
-    TestHook::LayoutGuard layout;
-    try
-    {
-        layout = TestHook::SetTerminalInputKeyboardLayout(L"00000409"); // US English
-    }
-    catch (...)
+    auto layout = TestHook::SetTerminalInputKeyboardLayout(L"00000409"); // US English
+    if (!layout)
     {
         Log::Result(TestResults::Result::Skipped);
         return;
diff --git a/src/terminal/adapter/ut_adapter/kittyKeyboardProtocol.cpp b/src/terminal/adapter/ut_adapter/kittyKeyboardProtocol.cpp
index ff01246365..44f5418701 100644
--- a/src/terminal/adapter/ut_adapter/kittyKeyboardProtocol.cpp
+++ b/src/terminal/adapter/ut_adapter/kittyKeyboardProtocol.cpp
@@ -258,11 +258,8 @@ class KittyKeyboardProtocolTests
 
     TEST_CLASS_SETUP(ClassSetup)
     {
-        try
-        {
-            layout = TestHook::SetTerminalInputKeyboardLayout(L"0001040c"); // French (Standard, AZERTY)
-        }
-        catch (...)
+        layout = TestHook::SetTerminalInputKeyboardLayout(L"0001040c"); // French (Standard, AZERTY)
+        if (!layout)
         {
             Log::Result(TestResults::Result::Skipped);
         }