Make the HWND one clear the same way as composition. Identify and temporarily resolve issue where device resources aren't created by conhost early enough for intersects to happen against the actual screen size. Mitigate issue where Present1 doesn't like being called if there isn't already ONE frame presented ever on the chain.

src/renderer/dx/DxRenderer.cpp

@@ -85,7 +85,8 @@ DxEngine::DxEngine() :
     _dpi{ USER_DEFAULT_SCREEN_DPI },
     _scale{ 1.0f },
     _chainMode{ SwapChainMode::ForComposition },
-    _customRenderer{ ::Microsoft::WRL::Make<CustomTextRenderer>() }
+    _customRenderer{ ::Microsoft::WRL::Make<CustomTextRenderer>() },
+    _hasEverPresented{ false }
 {
     TraceLoggingRegister(g_hDxRenderProvider);
 
@@ -153,6 +154,10 @@ DxEngine::~DxEngine()
     {
         _ReleaseDeviceResources();
     }
+    else
+    {
+        RETURN_IF_FAILED(_CreateDeviceResources(true));
+    }
 
     return S_OK;
 }
@@ -331,7 +336,7 @@ HRESULT DxEngine::_SetupTerminalEffects()
 // You can find out how to install it here:
 // https://docs.microsoft.com/en-us/windows/uwp/gaming/use-the-directx-runtime-and-visual-studio-graphics-diagnostic-features
                               // clang-format on
-                              // D3D11_CREATE_DEVICE_DEBUG |
+                              D3D11_CREATE_DEVICE_DEBUG |
                               D3D11_CREATE_DEVICE_SINGLETHREADED;
 
     const std::array<D3D_FEATURE_LEVEL, 5> FeatureLevels{ D3D_FEATURE_LEVEL_11_1,
@@ -434,6 +439,8 @@ HRESULT DxEngine::_SetupTerminalEffects()
                 THROW_HR(E_NOTIMPL);
             }
 
+            _hasEverPresented = false;
+
             if (_retroTerminalEffects)
             {
                 const HRESULT hr = _SetupTerminalEffects();
@@ -525,6 +532,9 @@ HRESULT DxEngine::_SetupTerminalEffects()
 
             RETURN_IF_FAILED(sc2->SetMatrixTransform(&inverseScale));
         }
+
+        _hasEverPresented = false;
+
         return S_OK;
     }
     CATCH_RETURN();
@@ -553,6 +563,7 @@ void DxEngine::_ReleaseDeviceResources() noexcept
 
         _dxgiSurface.Reset();
         _dxgiSwapChain.Reset();
+        _hasEverPresented = false;
 
         if (nullptr != _d3dDeviceContext.Get())
         {
@@ -1091,7 +1102,16 @@ void DxEngine::_InvalidOr(RECT rc) noexcept
         try
         {
             HRESULT hr = S_OK;
-            hr = _dxgiSwapChain->Present1(1, 0, &_presentParams);
+
+            if (_hasEverPresented)
+            {
+                hr = _dxgiSwapChain->Present1(1, 0, &_presentParams);
+            }
+            else
+            {
+                hr = _dxgiSwapChain->Present(1, 0);
+                _hasEverPresented = true;
+            }
 
             if (FAILED(hr))
             {
@@ -1148,9 +1168,6 @@ void DxEngine::_InvalidOr(RECT rc) noexcept
     switch (_chainMode)
     {
     case SwapChainMode::ForHwnd:
-        _d2dRenderTarget->FillRectangle(rect,
-                                        _d2dBrushBackground.Get());
-        break;
     case SwapChainMode::ForComposition:
         _d2dRenderTarget->PushAxisAlignedClip(rect,
                                               D2D1_ANTIALIAS_MODE::D2D1_ANTIALIAS_MODE_PER_PRIMITIVE);

src/renderer/dx/DxRenderer.hpp

@@ -149,6 +149,7 @@ namespace Microsoft::Console::Render
 
         void _InvalidOffset(POINT pt);
 
+        bool _hasEverPresented;
         bool _presentReady;
         RECT _presentDirty;
         RECT _presentScroll;