Only send DA requests to Xterm256 clients.

src/renderer/vt/Xterm256Engine.cpp

@@ -14,6 +14,20 @@ Xterm256Engine::Xterm256Engine(_In_ wil::unique_hfile hPipe,
 {
 }
 
+// Method Description:
+// - Sends a sequence to request the device attributes of the connected client.
+//   Flushes the buffer as well, to make sure the request is sent to the terminal.
+// Arguments:
+// - <none>
+// Return Value:
+// - S_OK if we succeeded, else an appropriate HRESULT.
+HRESULT Xterm256Engine::RequestDeviceAttributes() noexcept
+{
+    RETURN_IF_FAILED(_Write("\033[c"));
+    RETURN_IF_FAILED(_Flush());
+    return S_OK;
+}
+
 // Routine Description:
 // - Write a VT sequence to change the current colors of text. Writes true RGB
 //      color sequences.

src/renderer/vt/Xterm256Engine.hpp

@@ -30,6 +30,8 @@ namespace Microsoft::Console::Render
 
         virtual ~Xterm256Engine() override = default;
 
+        [[nodiscard]] HRESULT RequestDeviceAttributes() noexcept override;
+
         [[nodiscard]] HRESULT UpdateDrawingBrushes(const TextAttribute& textAttributes,
                                                    const RenderSettings& renderSettings,
                                                    const gsl::not_null<IRenderData*> pData,

src/renderer/vt/state.cpp

@@ -416,16 +416,14 @@ void VtEngine::SetTerminalOwner(Microsoft::Console::VirtualTerminal::VtIo* const
 
 // Method Description:
 // - Sends a sequence to request the device attributes of the connected client.
-//   Flushes the buffer as well, to make sure the request is sent to the terminal.
+//   This is not implemented by default. Only supported in the Xterm256 engine.
 // Arguments:
 // - <none>
 // Return Value:
-// - S_OK if we succeeded, else an appropriate HRESULT.
+// - S_OK if we succeeded, E_NOTIMPL if not implemented.
 HRESULT VtEngine::RequestDeviceAttributes() noexcept
 {
-    RETURN_IF_FAILED(_Write("\033[c"));
-    RETURN_IF_FAILED(_Flush());
-    return S_OK;
+    return E_NOTIMPL;
 }
 
 // Method Description:

src/renderer/vt/vtrenderer.hpp

@@ -75,7 +75,7 @@ namespace Microsoft::Console::Render
 
         // VtEngine
         [[nodiscard]] HRESULT SuppressResizeRepaint() noexcept;
-        [[nodiscard]] HRESULT RequestDeviceAttributes() noexcept;
+        [[nodiscard]] virtual HRESULT RequestDeviceAttributes() noexcept;
         [[nodiscard]] HRESULT RequestCursor() noexcept;
         [[nodiscard]] HRESULT InheritCursor(const til::point coordCursor) noexcept;
         [[nodiscard]] HRESULT WriteTerminalUtf8(const std::string_view str) noexcept;