app/internal/d3d11: detect hardware floating point support

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/internal/d3d11/backend_windows.go

@@ -20,6 +20,7 @@ type Device struct {
 	dev         *_ID3D11Device
 	ctx         *_ID3D11DeviceContext
 	featLvl     uint32
+	floatFormat uint32
 	depthStates map[depthState]*_ID3D11DepthStencilState
 	blendStates map[blendState]*_ID3D11BlendState
 }
@@ -116,8 +117,21 @@ func NewDevice() (*Device, error) {
 	dev := &Device{dev: d3ddev, ctx: d3dctx, featLvl: featLvl}
 	if featLvl < _D3D_FEATURE_LEVEL_9_1 {
 		_IUnknownRelease(unsafe.Pointer(d3ddev), d3ddev.vtbl.Release)
+		_IUnknownRelease(unsafe.Pointer(d3dctx), d3dctx.vtbl.Release)
 		return nil, fmt.Errorf("d3d11: feature level too low: %d", featLvl)
 	}
+	format := uint32(_DXGI_FORMAT_R16_FLOAT)
+	need := uint32(_D3D11_FORMAT_SUPPORT_TEXTURE2D | _D3D11_FORMAT_SUPPORT_RENDER_TARGET)
+	if use, _ := d3ddev.CheckFormatSupport(format); use&need == 0 {
+		// Fall back to a d3d 9.2 format.
+		format = _DXGI_FORMAT_R32_FLOAT
+		if use, _ = d3ddev.CheckFormatSupport(format); use&need == 0 {
+			_IUnknownRelease(unsafe.Pointer(d3ddev), d3ddev.vtbl.Release)
+			_IUnknownRelease(unsafe.Pointer(d3dctx), d3dctx.vtbl.Release)
+			return nil, fmt.Errorf("d3d11: no available floating point formats")
+		}
+	}
+	dev.floatFormat = format
 	dev.depthStates = make(map[depthState]*_ID3D11DepthStencilState)
 	dev.blendStates = make(map[blendState]*_ID3D11BlendState)
 	return dev, nil
@@ -257,7 +271,7 @@ func (b *Backend) NewTexture(format backend.TextureFormat, width, height int, mi
 	var d3dfmt uint32
 	switch format {
 	case backend.TextureFormatFloat:
-		d3dfmt = _DXGI_FORMAT_R16_FLOAT
+		d3dfmt = b.dev.floatFormat
 	case backend.TextureFormatSRGB:
 		d3dfmt = _DXGI_FORMAT_R8G8B8A8_UNORM_SRGB
 	default:

app/internal/d3d11/d3d11_windows.go

@@ -565,6 +565,11 @@ const (
 	_DXGI_FORMAT_R8G8B8A8_UNORM_SRGB = 29
 	_DXGI_FORMAT_R16_SINT            = 59
 	_DXGI_FORMAT_R16G16_SINT         = 38
+	_DXGI_FORMAT_R16_UINT            = 57
+	_DXGI_FORMAT_D24_UNORM_S8_UINT   = 45
+
+	_D3D11_FORMAT_SUPPORT_TEXTURE2D     = 0x20
+	_D3D11_FORMAT_SUPPORT_RENDER_TARGET = 0x4000
 
 	_DXGI_USAGE_RENDER_TARGET_OUTPUT = 1 << (1 + 4)
 
@@ -574,8 +579,6 @@ const (
 
 	_DXGI_SWAP_EFFECT_DISCARD = 0
 
-	_DXGI_FORMAT_R16_UINT = 57
-
 	_D3D_FEATURE_LEVEL_9_1  = 0x9100
 	_D3D_FEATURE_LEVEL_9_3  = 0x9300
 	_D3D_FEATURE_LEVEL_11_0 = 0xb000
@@ -611,8 +614,6 @@ const (
 	_D3D11_CLEAR_DEPTH   = 0x1
 	_D3D11_CLEAR_STENCIL = 0x2
 
-	_DXGI_FORMAT_D24_UNORM_S8_UINT = 45
-
 	_D3D11_DSV_DIMENSION_TEXTURE2D = 3
 
 	_D3D11_DEPTH_WRITE_MASK_ALL = 1
@@ -685,6 +686,21 @@ func _D3D11CreateDeviceAndSwapChain(driverType uint32, flags uint32, swapDesc *_
 	return dev, ctx, swchain, featLvl, nil
 }
 
+func (d *_ID3D11Device) CheckFormatSupport(format uint32) (uint32, error) {
+	var support uint32
+	r, _, _ := syscall.Syscall(
+		d.vtbl.CheckFormatSupport,
+		3,
+		uintptr(unsafe.Pointer(d)),
+		uintptr(format),
+		uintptr(unsafe.Pointer(&support)),
+	)
+	if r != 0 {
+		return 0, ErrorCode{Name: "ID3D11DeviceCheckFormatSupport", Code: uint32(r)}
+	}
+	return support, nil
+}
+
 func (d *_ID3D11Device) CreateBuffer(desc *_D3D11_BUFFER_DESC, data []byte) (*_ID3D11Buffer, error) {
 	var dataDesc *_D3D11_SUBRESOURCE_DATA
 	if len(data) > 0 {