Revert "internal/graphicsdriver/directx: remove tearing"

This reverts commit 78d3e4273b.

Reason: tearing is potentially risky but needed for maximizing FPS.
Also, tearing is officially recommended by Microsoft (see [1])

Closes #2697

[1] https://github.com/microsoft/DirectX-Graphics-Samples/blob/master/Samples/Desktop/D3D12Raytracing/src/D3D12RaytracingHelloWorld/DeviceResources.cpp#L520

internal/graphicsdriver/directx/dxgi_windows.go

@@ -35,6 +35,12 @@ const (
 
 type _DXGI_COLOR_SPACE_TYPE int32
 
+type _DXGI_FEATURE int32
+
+const (
+	_DXGI_FEATURE_PRESENT_ALLOW_TEARING _DXGI_FEATURE = 0
+)
+
 type _DXGI_FORMAT int32
 
 const (
@@ -55,10 +61,17 @@ type _DXGI_PRESENT uint32
 
 const (
 	_DXGI_PRESENT_TEST          _DXGI_PRESENT = 0x00000001
+	_DXGI_PRESENT_ALLOW_TEARING _DXGI_PRESENT = 0x00000200
 )
 
 type _DXGI_SCALING int32
 
+type _DXGI_SWAP_CHAIN_FLAG int32
+
+const (
+	_DXGI_SWAP_CHAIN_FLAG_ALLOW_TEARING _DXGI_SWAP_CHAIN_FLAG = 2048
+)
+
 type _DXGI_SWAP_EFFECT int32
 
 const (
@@ -90,6 +103,7 @@ var (
 	_IID_IDXGIDevice     = windows.GUID{Data1: 0x54ec77fa, Data2: 0x1377, Data3: 0x44e6, Data4: [...]byte{0x8c, 0x32, 0x88, 0xfd, 0x5f, 0x44, 0xc8, 0x4c}}
 	_IID_IDXGIFactory    = windows.GUID{Data1: 0x7b7166ec, Data2: 0x21c7, Data3: 0x44ae, Data4: [...]byte{0xb2, 0x1a, 0xc9, 0xae, 0x32, 0x1a, 0xe3, 0x69}}
 	_IID_IDXGIFactory4   = windows.GUID{Data1: 0x1bc6ea02, Data2: 0xef36, Data3: 0x464f, Data4: [...]byte{0xbf, 0x0c, 0x21, 0xca, 0x39, 0xe5, 0x16, 0x8a}}
+	_IID_IDXGIFactory5   = windows.GUID{Data1: 0x7632e1f5, Data2: 0xee65, Data3: 0x4dca, Data4: [...]byte{0x87, 0xfd, 0x84, 0xcd, 0x75, 0xf8, 0x83, 0x8d}}
 	_IID_IDXGISwapChain4 = windows.GUID{Data1: 0x3d585d5a, Data2: 0xbd4a, Data3: 0x489e, Data4: [...]byte{0xb1, 0xf4, 0x3d, 0xbc, 0xb6, 0x45, 0x2f, 0xfb}}
 )
 
@@ -387,6 +401,59 @@ func (i *_IDXGIFactory4) Release() uint32 {
 	return uint32(r)
 }
 
+type _IDXGIFactory5 struct {
+	vtbl *_IDXGIFactory5_Vtbl
+}
+
+type _IDXGIFactory5_Vtbl struct {
+	QueryInterface uintptr
+	AddRef         uintptr
+	Release        uintptr
+
+	SetPrivateData                uintptr
+	SetPrivateDataInterface       uintptr
+	GetPrivateData                uintptr
+	GetParent                     uintptr
+	EnumAdapters                  uintptr
+	MakeWindowAssociation         uintptr
+	GetWindowAssociation          uintptr
+	CreateSwapChain               uintptr
+	CreateSoftwareAdapter         uintptr
+	EnumAdapters1                 uintptr
+	IsCurrent                     uintptr
+	IsWindowedStereoEnabled       uintptr
+	CreateSwapChainForHwnd        uintptr
+	CreateSwapChainForCoreWindow  uintptr
+	GetSharedResourceAdapterLuid  uintptr
+	RegisterStereoStatusWindow    uintptr
+	RegisterStereoStatusEvent     uintptr
+	UnregisterStereoStatus        uintptr
+	RegisterOcclusionStatusWindow uintptr
+	RegisterOcclusionStatusEvent  uintptr
+	UnregisterOcclusionStatus     uintptr
+	CreateSwapChainForComposition uintptr
+	GetCreationFlags              uintptr
+	EnumAdapterByLuid             uintptr
+	EnumWarpAdapter               uintptr
+	CheckFeatureSupport           uintptr
+}
+
+func (i *_IDXGIFactory5) CheckFeatureSupport(feature _DXGI_FEATURE, pFeatureSupportData unsafe.Pointer, featureSupportDataSize uint32) error {
+	r, _, _ := syscall.Syscall6(i.vtbl.CheckFeatureSupport, 4, uintptr(unsafe.Pointer(i)),
+		uintptr(feature), uintptr(pFeatureSupportData), uintptr(featureSupportDataSize),
+		0, 0)
+	runtime.KeepAlive(pFeatureSupportData)
+	if uint32(r) != uint32(windows.S_OK) {
+		return fmt.Errorf("directx: IDXGIFactory5::CheckFeatureSupport failed: %w", handleError(windows.Handle(uint32(r))))
+	}
+	return nil
+}
+
+func (i *_IDXGIFactory5) Release() uint32 {
+	r, _, _ := syscall.Syscall(i.vtbl.Release, 1, uintptr(unsafe.Pointer(i)), 0, 0)
+	return uint32(r)
+}
+
 type _IDXGIOutput struct {
 	vtbl *_IDXGIOutput_Vtbl
 }

internal/graphicsdriver/directx/graphics_windows.go

@@ -150,6 +150,8 @@ type graphicsInfra struct {
 	swapChain  *_IDXGISwapChain
 	swapChain4 *_IDXGISwapChain4
 
+	allowTearing bool
+
 	// occluded reports whether the screen is invisible or not.
 	occluded bool
 
@@ -166,6 +168,16 @@ func newGraphicsInfra(factory *_IDXGIFactory) (*graphicsInfra, error) {
 	}
 	runtime.SetFinalizer(g, (*graphicsInfra).release)
 
+	if f, err := g.factory.QueryInterface(&_IID_IDXGIFactory5); err == nil && f != nil {
+		factory := (*_IDXGIFactory5)(f)
+		defer factory.Release()
+
+		var allowTearing int32
+		if err := factory.CheckFeatureSupport(_DXGI_FEATURE_PRESENT_ALLOW_TEARING, unsafe.Pointer(&allowTearing), uint32(unsafe.Sizeof(allowTearing))); err == nil && allowTearing != 0 {
+			g.allowTearing = true
+		}
+	}
+
 	return g, nil
 }
 
@@ -266,6 +278,10 @@ func (g *graphicsInfra) initSwapChain(width, height int, device unsafe.Pointer,
 	}
 
 	g.bufferCount = int(desc.BufferCount)
+
+	if g.allowTearing {
+		desc.Flags |= uint32(_DXGI_SWAP_CHAIN_FLAG_ALLOW_TEARING)
+	}
 	s, err := g.factory.CreateSwapChain(device, desc)
 	if err != nil {
 		return err
@@ -295,7 +311,11 @@ func (g *graphicsInfra) resizeSwapChain(width, height int) error {
 		return fmt.Errorf("directx: swap chain must be initialized at resizeSwapChain, but is not")
 	}
 
-	if err := g.swapChain.ResizeBuffers(uint32(g.bufferCount), uint32(width), uint32(height), _DXGI_FORMAT_B8G8R8A8_UNORM, 0); err != nil {
+	var flag uint32
+	if g.allowTearing {
+		flag |= uint32(_DXGI_SWAP_CHAIN_FLAG_ALLOW_TEARING)
+	}
+	if err := g.swapChain.ResizeBuffers(uint32(g.bufferCount), uint32(width), uint32(height), _DXGI_FORMAT_B8G8R8A8_UNORM, flag); err != nil {
 		return err
 	}
 	return nil
@@ -322,6 +342,8 @@ func (g *graphicsInfra) present(vsyncEnabled bool) error {
 		// Do actual rendering only when the screen is visible.
 		if vsyncEnabled {
 			syncInterval = 1
+		} else if g.allowTearing {
+			flags |= _DXGI_PRESENT_ALLOW_TEARING
 		}
 	}