There's no reason that this should have entirely broken moving panes.…

… That doesn't make sense.

src/cascadia/TerminalControl/ControlCore.cpp

@@ -1555,19 +1555,32 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         _RendererWarningHandlers(*this, winrt::make<RendererWarningArgs>(hr));
     }
 
-    void ControlCore::_renderEngineSwapChainChanged(const HANDLE handle)
+    winrt::fire_and_forget ControlCore::_renderEngineSwapChainChanged(const HANDLE sourceHandle)
     {
-        // `handle` is a weak ref to a HANDLE that's ultimately owned by the
+        // `sourceHandle` is a weak ref to a HANDLE that's ultimately owned by the
         // render engine's own unique_handle. We'll add another ref to it here.
         // This will make sure that we always have a valid HANDLE to give to
         // callers of our own SwapChainHandle method, even if the renderer is
         // currently in the process of discarding this value and creating a new
         // one. Callers should have already set up the SwapChainChanged
         // callback, so this all works out.
-        _lastSwapChainHandle.attach(handle);
 
-        // Now bubble the event up to the control.
-        _SwapChainChangedHandlers(*this, winrt::box_value<uint64_t>(reinterpret_cast<uint64_t>(handle)));
+        winrt::handle duplicatedHandle;
+        const auto processHandle = GetCurrentProcess();
+        THROW_IF_WIN32_BOOL_FALSE(DuplicateHandle(processHandle, sourceHandle, processHandle, duplicatedHandle.put(), 0, FALSE, DUPLICATE_SAME_ACCESS));
+
+        const auto weakThis{ get_weak() };
+
+        co_await wil::resume_foreground(_dispatcher);
+
+        if (auto core{ weakThis.get() })
+        {
+            // `this` is safe to use now
+
+            _lastSwapChainHandle = (std::move(duplicatedHandle));
+            // Now bubble the event up to the control.
+            _SwapChainChangedHandlers(*this, winrt::box_value<uint64_t>(reinterpret_cast<uint64_t>(_lastSwapChainHandle.get())));
+        }
     }
 
     void ControlCore::_rendererBackgroundColorChanged()

src/cascadia/TerminalControl/ControlCore.h

@@ -328,7 +328,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
 #pragma region RendererCallbacks
         void _rendererWarning(const HRESULT hr);
-        void _renderEngineSwapChainChanged(const HANDLE handle);
+        winrt::fire_and_forget _renderEngineSwapChainChanged(const HANDLE handle);
         void _rendererBackgroundColorChanged();
         void _rendererTabColorChanged();
 #pragma endregion

src/cascadia/TerminalControl/TermControl.cpp

@@ -866,28 +866,11 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         return _core.ConnectionState();
     }
 
-    winrt::fire_and_forget TermControl::RenderEngineSwapChainChanged(IInspectable /*sender*/, IInspectable args)
+    void TermControl::RenderEngineSwapChainChanged(IInspectable /*sender*/, IInspectable args)
     {
-        // This event comes in on the render thread, not the UI thread.
-
-        const auto weakThis{ get_weak() };
-
-        winrt::handle handle;
-
-        // Add a ref to the handle passed to us, so that the HANDLE will remain
-        // valid to the other side of the co_await.
-        handle.attach(reinterpret_cast<HANDLE>(winrt::unbox_value<uint64_t>(args)));
-
-        co_await wil::resume_foreground(Dispatcher());
-
-        if (auto control{ weakThis.get() })
-        {
-            _AttachDxgiSwapChainToXaml(handle.get());
-        }
-        // Detach from the handle. If you don't do this, we'll CloseHandle() on
-        // the handle when `handle` goes out of scope, resulting in the swap
-        // chain being closed.
-        handle.detach();
+        // This event comes in on the UI thread
+        HANDLE h = reinterpret_cast<HANDLE>(winrt::unbox_value<uint64_t>(args));
+        _AttachDxgiSwapChainToXaml(h);
     }
 
     // Method Description:
@@ -1818,7 +1801,11 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         // GH#5421: Enable the UiaEngine before checking for the SearchBox
         // That way, new selections are notified to automation clients.
         // The _uiaEngine lives in _interactivity, so call into there to enable it.
-        _interactivity.GotFocus();
+
+        if (_interactivity)
+        {
+            _interactivity.GotFocus();
+        }
 
         // If the searchbox is focused, we don't want TSFInputControl to think
         // it has focus so it doesn't intercept IME input. We also don't want the
@@ -1873,7 +1860,10 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
         // This will disable the accessibility notifications, because the
         // UiaEngine lives in ControlInteractivity
-        _interactivity.LostFocus();
+        if (_interactivity)
+        {
+            _interactivity.LostFocus();
+        }
 
         if (TSFInputControl() != nullptr)
         {

src/cascadia/TerminalControl/TermControl.h

@@ -95,7 +95,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
 
         void ToggleShaderEffects();
 
-        winrt::fire_and_forget RenderEngineSwapChainChanged(IInspectable sender, IInspectable args);
+        void RenderEngineSwapChainChanged(IInspectable sender, IInspectable args);
         void _AttachDxgiSwapChainToXaml(HANDLE swapChainHandle);
         winrt::fire_and_forget _RendererEnteredErrorState(IInspectable sender, IInspectable args);