internal/graphicsdriver/directx: allow tearing when vsync is off

Updates #2034
Updates #2188

internal/graphicsdriver/directx/api_windows.go

@@ -577,6 +577,12 @@ 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 (
@@ -593,8 +599,20 @@ type _DXGI_MODE_SCANLINE_ORDER int32
 
 type _DXGI_MODE_SCALING int32
 
+type _DXGI_PRESENT uint32
+
+const (
+	_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 (
@@ -634,6 +652,7 @@ var (
 	_IID_IDXGIAdapter1 = windows.GUID{Data1: 0x29038f61, Data2: 0x3839, Data3: 0x4626, Data4: [...]byte{0x91, 0xfd, 0x08, 0x68, 0x79, 0x01, 0x1a, 0x05}}
 	_IID_IDXGIDevice   = windows.GUID{Data1: 0x54ec77fa, Data2: 0x1377, Data3: 0x44e6, Data4: [...]byte{0x8c, 0x32, 0x88, 0xfd, 0x5f, 0x44, 0xc8, 0x4c}}
 	_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}}
 )
 
 type _D3D12_BLEND_DESC struct {
@@ -2429,10 +2448,72 @@ func (i *_IDXGIFactory4) MakeWindowAssociation(windowHandle windows.HWND, flags
 	return nil
 }
 
+func (i *_IDXGIFactory4) QueryInterface(riid *windows.GUID, ppvObject *unsafe.Pointer) error {
+	r, _, _ := syscall.Syscall(i.vtbl.QueryInterface, 3, uintptr(unsafe.Pointer(i)), uintptr(unsafe.Pointer(riid)), uintptr(unsafe.Pointer(ppvObject)))
+	runtime.KeepAlive(riid)
+	runtime.KeepAlive(ppvObject)
+	if uint32(r) != uint32(windows.S_OK) {
+		return fmt.Errorf("directx: IDXGIFactory4::QueryInterface failed: HRESULT(%d)", uint32(r))
+	}
+	return nil
+}
+
 func (i *_IDXGIFactory4) Release() {
 	syscall.Syscall(i.vtbl.Release, 1, uintptr(unsafe.Pointer(i)), 0, 0)
 }
 
+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: HRESULT(%d)", uint32(r))
+	}
+	return nil
+}
+
+func (i *_IDXGIFactory5) Release() {
+	syscall.Syscall(i.vtbl.Release, 1, uintptr(unsafe.Pointer(i)), 0, 0)
+}
+
 type _IDXGIOutput struct {
 	vtbl *_IDXGIOutput_Vtbl
 }

internal/graphicsdriver/directx/graphics_windows.go

@@ -103,6 +103,8 @@ type Graphics struct {
 	fenceValues    [frameCount]uint64
 	fenceWaitEvent windows.Handle
 
+	allowTearing bool
+
 	// drawCommandAllocators are command allocators for a 3D engine (DrawIndexedInstanced).
 	// For the word 'engine', see https://docs.microsoft.com/en-us/windows/win32/direct3d12/user-mode-heap-synchronization.
 	// The term 'draw' is used instead of '3D' in this package.
@@ -268,6 +270,15 @@ func (g *Graphics) initializeDesktop(useWARP bool, useDebugLayer bool) (ferr err
 		return err
 	}
 
+	var factory *_IDXGIFactory5
+	if err := g.factory.QueryInterface(&_IID_IDXGIFactory5, (*unsafe.Pointer)(unsafe.Pointer(&factory))); err == nil && factory != nil {
+		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
+		}
+	}
+
 	if err := g.initializeMembers(); err != nil {
 		return err
 	}
@@ -524,7 +535,7 @@ func (g *Graphics) initSwapChainDesktop(width, height int) (ferr error) {
 	//
 	//     IDXGIFactory::CreateSwapChain: Alpha blended swapchains must be created with CreateSwapChainForComposition,
 	//     or CreateSwapChainForCoreWindow with the DXGI_SWAP_CHAIN_FLAG_FOREGROUND_LAYER flag
-	s, err := g.factory.CreateSwapChainForHwnd(unsafe.Pointer(g.commandQueue), g.window, &_DXGI_SWAP_CHAIN_DESC1{
+	desc := &_DXGI_SWAP_CHAIN_DESC1{
 		Width:       uint32(width),
 		Height:      uint32(height),
 		Format:      _DXGI_FORMAT_B8G8R8A8_UNORM,
@@ -535,7 +546,11 @@ func (g *Graphics) initSwapChainDesktop(width, height int) (ferr error) {
 			Count:   1,
 			Quality: 0,
 		},
-	}, nil, nil)
+	}
+	if g.allowTearing {
+		desc.Flags |= uint32(_DXGI_SWAP_CHAIN_FLAG_ALLOW_TEARING)
+	}
+	s, err := g.factory.CreateSwapChainForHwnd(unsafe.Pointer(g.commandQueue), g.window, desc, nil, nil)
 	if err != nil {
 		return err
 	}
@@ -781,10 +796,13 @@ func (g *Graphics) presentDesktop() error {
 	}
 
 	var syncInterval uint32
+	var flags _DXGI_PRESENT
 	if g.vsyncEnabled {
 		syncInterval = 1
+	} else if g.allowTearing {
+		flags |= _DXGI_PRESENT_ALLOW_TEARING
 	}
-	if err := g.swapChain.Present(syncInterval, 0); err != nil {
+	if err := g.swapChain.Present(syncInterval, uint32(flags)); err != nil {
 		return err
 	}