Only load default terminal choice on OS builds where it should work.

.github/actions/spelling/expect/expect.txt

@@ -170,6 +170,7 @@ blog
 Blt
 BLUESCROLL
 bmp
+BODGY
 BOLDFONT
 BOOLIFY
 bools

src/cascadia/TerminalSettingsEditor/Launch.cpp

@@ -19,6 +19,15 @@ namespace winrt::Microsoft::Terminal::Settings::Editor::implementation
 
         INITIALIZE_BINDABLE_ENUM_SETTING(LaunchMode, LaunchMode, LaunchMode, L"Globals_LaunchMode", L"Content");
         INITIALIZE_BINDABLE_ENUM_SETTING(WindowingBehavior, WindowingMode, WindowingMode, L"Globals_WindowingBehavior", L"Content");
+
+        // BODGY
+        // Xaml code generator for x:Bind to this will fail to find UnloadObject() on Launch class.
+        // To work around, check it ourselves on construction and FindName to force load.
+        // It's specified as x:Load=false in the XAML. So it only loads if this passes.
+        if (CascadiaSettings::IsDefaultTerminalAvailable())
+        {
+            FindName(L"DefaultTerminalDropdown");
+        }
     }
 
     void Launch::OnNavigatedTo(const NavigationEventArgs& e)

src/cascadia/TerminalSettingsEditor/Launch.xaml

@@ -70,7 +70,10 @@
                 </local:SettingContainer>
 
                 <!--  Default Terminal  -->
-                <local:SettingContainer x:Uid="Globals_DefaultTerminal">
+                <local:SettingContainer x:Uid="Globals_DefaultTerminal"
+                                        x:Name="DefaultTerminalDropdown"
+                                        x:Load="false"
+                                        >
                     <ComboBox x:Name="DefaultTerminal"
                               ItemsSource="{x:Bind State.Settings.DefaultTerminals, Mode=OneWay}"
                               SelectedItem="{x:Bind State.Settings.CurrentDefaultTerminal, Mode=TwoWay}"

src/cascadia/TerminalSettingsModel/CascadiaSettings.cpp

@@ -1023,6 +1023,33 @@ void CascadiaSettings::RefreshDefaultTerminals()
     _currentDefaultTerminal = Model::DefaultTerminal::Current();
 }
 
+// Helper to do the version check 
+static bool _isOnBuildWithDefTerm() noexcept
+{
+    OSVERSIONINFOEXW osver{ 0 };
+    osver.dwOSVersionInfoSize = sizeof(osver);
+    osver.dwBuildNumber = 21359;
+
+    DWORDLONG dwlConditionMask = 0;
+    VER_SET_CONDITION(dwlConditionMask, VER_BUILDNUMBER, VER_GREATER_EQUAL);
+
+    return VerifyVersionInfoW(&osver, VER_BUILDNUMBER, dwlConditionMask);
+}
+
+// Method Description:
+// - Determines if we're on an OS platform that supports
+//   the default terminal handoff functionality.
+// Arguments:
+// - <none>
+// Return Value:
+// - True if OS supports default termianl. False otherwise.
+bool CascadiaSettings::IsDefaultTerminalAvailable() noexcept
+{
+    // Cached on first use since the OS version shouldn't change while we're running.
+    static bool isAvailable = _isOnBuildWithDefTerm();
+    return isAvailable;
+}
+
 // Method Description:
 // - Returns an iterable collection of all available terminals.
 // Arguments:

src/cascadia/TerminalSettingsModel/CascadiaSettings.h

@@ -100,6 +100,7 @@ namespace winrt::Microsoft::Terminal::Settings::Model::implementation
 
         void RefreshDefaultTerminals();
 
+        static bool IsDefaultTerminalAvailable() noexcept;
         Windows::Foundation::Collections::IObservableVector<Model::DefaultTerminal> DefaultTerminals() const noexcept;
         Model::DefaultTerminal CurrentDefaultTerminal() const noexcept;
         void CurrentDefaultTerminal(Model::DefaultTerminal terminal);

src/cascadia/TerminalSettingsModel/CascadiaSettings.idl

@@ -45,6 +45,7 @@ namespace Microsoft.Terminal.Settings.Model
         Guid GetProfileForArgs(NewTerminalArgs newTerminalArgs);
 
         void RefreshDefaultTerminals();
+        static Boolean IsDefaultTerminalAvailable { get; };
         Windows.Foundation.Collections.IObservableVector<DefaultTerminal> DefaultTerminals { get; };
         DefaultTerminal CurrentDefaultTerminal;
     }