From 6e6f2859ab8874825452ee852f1b1c6923aead09 Mon Sep 17 00:00:00 2001
From: Ari Vuollet <ari.vuollet@kapsi.fi>
Date: Sat, 26 Mar 2022 16:48:02 +0200
Subject: [PATCH] Fix switching to fullscreen mode in D3D11/D3D12 flip
 presentation modes

---
 .../DirectX/DX11/GPUDeviceDX11.cpp            | 19 ++++++++-----------
 .../DirectX/DX11/GPUSwapChainDX11.cpp         | 12 +++++++++++-
 .../DirectX/DX12/GPUSwapChainDX12.cpp         | 12 +++++++++++-
 .../Engine/Platform/Windows/WindowsWindow.cpp | 10 ++++++++++
 4 files changed, 40 insertions(+), 13 deletions(-)

diff --git a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUDeviceDX11.cpp b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUDeviceDX11.cpp
index 35d2253a2..aadac4abf 100644
--- a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUDeviceDX11.cpp
+++ b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUDeviceDX11.cpp
@@ -265,18 +265,15 @@ bool GPUDeviceDX11::Init()
         return true;
     }
     UpdateOutputs(adapter);
+
+    ComPtr<IDXGIFactory5> factory5;
+    _factoryDXGI->QueryInterface(IID_PPV_ARGS(&factory5));
+    if (factory5)
     {
-        ComPtr<IDXGIFactory5> factory5;
-        _factoryDXGI->QueryInterface(IID_PPV_ARGS(&factory5));
-        if (factory5)
-        {
-            BOOL allowTearing;
-            if (SUCCEEDED(factory5->CheckFeatureSupport(DXGI_FEATURE_PRESENT_ALLOW_TEARING, &allowTearing, sizeof(allowTearing))) && allowTearing)
-            {
-                AllowTearing = true;
-            }
-            factory5->Release();
-        }
+        BOOL allowTearing;
+        if (SUCCEEDED(factory5->CheckFeatureSupport(DXGI_FEATURE_PRESENT_ALLOW_TEARING, &allowTearing, sizeof(allowTearing))) && allowTearing)
+            AllowTearing = true;
+        factory5->Release();
     }
 
 
diff --git a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUSwapChainDX11.cpp b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUSwapChainDX11.cpp
index 79e76a2a5..c7b884c59 100644
--- a/Source/Engine/GraphicsDevice/DirectX/DX11/GPUSwapChainDX11.cpp
+++ b/Source/Engine/GraphicsDevice/DirectX/DX11/GPUSwapChainDX11.cpp
@@ -112,6 +112,16 @@ void GPUSwapChainDX11::SetFullscreen(bool isFullscreen)
         }
 
         _isFullscreen = isFullscreen;
+
+        // Buffers must be resized in flip presentation model
+        if (swapChainDesc.SwapEffect == DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL ||
+            swapChainDesc.SwapEffect == DXGI_SWAP_EFFECT_FLIP_DISCARD)
+        {
+            const int32 width = _width;
+            const int32 height = _height;
+            _width = _height = 0;
+            Resize(width, height);
+        }
     }
 #else
     LOG(Info, "Cannot change fullscreen mode on this platform");
@@ -218,7 +228,7 @@ bool GPUSwapChainDX11::Resize(int32 width, int32 height)
         ASSERT(_swapChain);
 
         // Disable DXGI changes to the window
-        VALIDATE_DIRECTX_RESULT(dxgi->MakeWindowAssociation(_windowHandle, 0));
+        VALIDATE_DIRECTX_RESULT(dxgi->MakeWindowAssociation(_windowHandle, DXGI_MWA_NO_ALT_ENTER));
 #else
         auto dxgiFactory = (IDXGIFactory2*)_device->GetDXGIFactory();
         VALIDATE_DIRECTX_RESULT(dxgiFactory->CreateSwapChainForCoreWindow(_device->GetDevice(), static_cast<IUnknown*>(_windowHandle), &swapChainDesc, nullptr, &_swapChain));
diff --git a/Source/Engine/GraphicsDevice/DirectX/DX12/GPUSwapChainDX12.cpp b/Source/Engine/GraphicsDevice/DirectX/DX12/GPUSwapChainDX12.cpp
index 18b1af930..e7e976987 100644
--- a/Source/Engine/GraphicsDevice/DirectX/DX12/GPUSwapChainDX12.cpp
+++ b/Source/Engine/GraphicsDevice/DirectX/DX12/GPUSwapChainDX12.cpp
@@ -137,6 +137,16 @@ void GPUSwapChainDX12::SetFullscreen(bool isFullscreen)
         }
 
         _isFullscreen = isFullscreen;
+
+        // Buffers must be resized in flip presentation model
+        if (swapChainDesc.SwapEffect == DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL ||
+            swapChainDesc.SwapEffect == DXGI_SWAP_EFFECT_FLIP_DISCARD)
+        {
+            const int32 width = _width;
+            const int32 height = _height;
+            _width = _height = 0;
+            Resize(width, height);
+        }
     }
 #else
     LOG(Info, "Cannot change fullscreen mode on this platform");
@@ -219,7 +229,7 @@ bool GPUSwapChainDX12::Resize(int32 width, int32 height)
         _backBuffers.Resize(swapChainDesc.BufferCount);
 
         // Disable DXGI changes to the window
-        dxgiFactory->MakeWindowAssociation(_windowHandle, 0);
+        VALIDATE_DIRECTX_RESULT(dxgiFactory->MakeWindowAssociation(_windowHandle, DXGI_MWA_NO_ALT_ENTER));
     }
     else
     {
diff --git a/Source/Engine/Platform/Windows/WindowsWindow.cpp b/Source/Engine/Platform/Windows/WindowsWindow.cpp
index 50f092407..cb1617219 100644
--- a/Source/Engine/Platform/Windows/WindowsWindow.cpp
+++ b/Source/Engine/Platform/Windows/WindowsWindow.cpp
@@ -1031,6 +1031,10 @@ LRESULT WindowsWindow::WndProc(UINT msg, WPARAM wParam, LPARAM lParam)
                     // In this case, we don't resize yet -- we wait until the user stops dragging, and a WM_EXITSIZEMOVE message comes.
                     UpdateRegion();
                 }
+                else if (_isSwitchingFullScreen)
+                {
+                    // Ignored
+                }
                 else
                 {
                     // This WM_SIZE come from resizing the window via an API like SetWindowPos() so resize
@@ -1090,6 +1094,12 @@ LRESULT WindowsWindow::WndProc(UINT msg, WPARAM wParam, LPARAM lParam)
             Close(ClosingReason::User);
             return 0;
         }
+        if (wParam == VK_RETURN)
+        {
+            LOG(Info, "Alt+Enter pressed");
+            SetIsFullscreen(!IsFullscreen());
+            return 0;
+        }
         break;
     case WM_POWERBROADCAST:
         switch (wParam)