Enable flip presentation mode and tearing in D3D11

Source/Engine/GraphicsDevice/DirectX/DX11/GPUDeviceDX11.cpp

@@ -265,6 +265,19 @@ bool GPUDeviceDX11::Init()
         return true;
     }
     UpdateOutputs(adapter);
+    {
+        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;
+            }
+        }
+    }
+
 
     // Get flags and device type base on current configuration
     uint32 flags = D3D11_CREATE_DEVICE_BGRA_SUPPORT;

Source/Engine/GraphicsDevice/DirectX/DX11/GPUDeviceDX11.h

@@ -50,6 +50,10 @@ public:
     GPUDeviceDX11(IDXGIFactory* dxgiFactory, GPUAdapterDX* adapter);
     ~GPUDeviceDX11();
 
+public:
+
+    bool AllowTearing = false;
+
 public:
 
     // Gets DX11 device

Source/Engine/GraphicsDevice/DirectX/DX11/GPUSwapChainDX11.cpp

@@ -17,6 +17,8 @@ GPUSwapChainDX11::GPUSwapChainDX11(GPUDeviceDX11* device, Window* window)
 #endif
     , _swapChain(nullptr)
     , _backBuffer(nullptr)
+    , _allowTearing(false)
+    , _isFullscreen(false)
 {
     ASSERT(_windowHandle);
     _window = window;
@@ -108,6 +110,8 @@ void GPUSwapChainDX11::SetFullscreen(bool isFullscreen)
         {
             LOG(Warning, "Cannot change fullscreen mode for '{0}' to {1}.", ToString(), isFullscreen);
         }
+
+        _isFullscreen = isFullscreen;
     }
 #else
     LOG(Info, "Cannot change fullscreen mode on this platform");
@@ -123,7 +127,12 @@ void GPUSwapChainDX11::Present(bool vsync)
 {
     // Present frame
     ASSERT(_swapChain);
-    const HRESULT result = _swapChain->Present(vsync ? 1 : 0, 0);
+    UINT presentFlags = 0;
+    if (!vsync && !_isFullscreen && _allowTearing)
+    {
+        presentFlags |= DXGI_PRESENT_ALLOW_TEARING;
+    }
+    const HRESULT result = _swapChain->Present(vsync ? 1 : 0, presentFlags);
     LOG_DIRECTX_RESULT(result);
 
     // Base
@@ -140,6 +149,7 @@ bool GPUSwapChainDX11::Resize(int32 width, int32 height)
 
     _device->WaitForGPU();
     GPUDeviceLock lock(_device);
+    _allowTearing = _device->AllowTearing;
     _format = GPU_BACK_BUFFER_PIXEL_FORMAT;
 
 #if PLATFORM_WINDOWS
@@ -177,6 +187,12 @@ bool GPUSwapChainDX11::Resize(int32 width, int32 height)
         swapChainDesc.Windowed = TRUE;
         swapChainDesc.SwapEffect = DXGI_SWAP_EFFECT_DISCARD;
         swapChainDesc.Flags = DXGI_SWAP_CHAIN_FLAG_ALLOW_MODE_SWITCH;
+
+        if (_allowTearing)
+        {
+            swapChainDesc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_DISCARD;
+            swapChainDesc.Flags |= DXGI_SWAP_CHAIN_FLAG_ALLOW_TEARING;
+        }
 #else
         swapChainDesc.Width = width;
         swapChainDesc.Height = height;

Source/Engine/GraphicsDevice/DirectX/DX11/GPUSwapChainDX11.h

@@ -23,6 +23,7 @@ private:
 #if PLATFORM_WINDOWS
     HWND _windowHandle;
     IDXGISwapChain* _swapChain;
+    bool _allowTearing, _isFullscreen;
 #else
 	IUnknown* _windowHandle;
 	IDXGISwapChain1* _swapChain;

Source/Engine/GraphicsDevice/DirectX/IncludeDirectXHeaders.h

@@ -39,6 +39,7 @@ typedef IGraphicsUnknown IDXGISwapChain3;
 #include <D3D11.h>
 #include <d3d11_1.h>
 #include <dxgi1_3.h>
+#include <dxgi1_5.h>
 #endif
 #if GRAPHICS_API_DIRECTX12
 #include <dxgi1_5.h>