gpu/internal/driver: rename gpu/backend

There are no longer any importers of package backend outside of
gioui.org/gpu. Move it internally, and rename it to the slightly more
specific "driver" while we're at it.

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

gpu/internal/driver/api.go

@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package driver
+
+import (
+	"fmt"
+	"unsafe"
+
+	"gioui.org/internal/glimpl"
+)
+
+// See gpu/api.go for documentation for the API types
+
+type API interface {
+	implementsAPI()
+}
+
+type OpenGL struct {
+	// Context contains the WebGL context for WebAssembly platforms. It is
+	// empty for all other platforms; an OpenGL context is assumed current when
+	// calling NewDevice.
+	Context glimpl.Context
+}
+
+type Direct3D11 struct {
+	// Device contains a *ID3D11Device.
+	Device unsafe.Pointer
+}
+
+// API specific device constructors.
+var (
+	NewOpenGLDevice     func(api OpenGL) (Device, error)
+	NewDirect3D11Device func(api Direct3D11) (Device, error)
+)
+
+// NewDevice creates a new Device given the api.
+//
+// Note that the device does not assume ownership of the resources contained in
+// api; the caller must ensure the resources are valid until the device is
+// released.
+func NewDevice(api API) (Device, error) {
+	switch api := api.(type) {
+	case OpenGL:
+		if NewOpenGLDevice != nil {
+			return NewOpenGLDevice(api)
+		}
+	case Direct3D11:
+		if NewDirect3D11Device != nil {
+			return NewDirect3D11Device(api)
+		}
+	}
+	return nil, fmt.Errorf("driver: no driver available for the API %T", api)
+}
+
+func (OpenGL) implementsAPI()     {}
+func (Direct3D11) implementsAPI() {}

gpu/internal/driver/backend.go

@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package driver
+
+import (
+	"errors"
+	"image"
+	"time"
+)
+
+// Device represents the abstraction of underlying GPU
+// APIs such as OpenGL, Direct3D useful for rendering Gio
+// operations.
+type Device interface {
+	BeginFrame() Framebuffer
+	EndFrame()
+	Caps() Caps
+	NewTimer() Timer
+	// IsContinuousTime reports whether all timer measurements
+	// are valid at the point of call.
+	IsTimeContinuous() bool
+	NewTexture(format TextureFormat, width, height int, minFilter, magFilter TextureFilter, bindings BufferBinding) (Texture, error)
+	NewFramebuffer(tex Texture, depthBits int) (Framebuffer, error)
+	NewImmutableBuffer(typ BufferBinding, data []byte) (Buffer, error)
+	NewBuffer(typ BufferBinding, size int) (Buffer, error)
+	NewComputeProgram(shader ShaderSources) (Program, error)
+	NewProgram(vertexShader, fragmentShader ShaderSources) (Program, error)
+	NewInputLayout(vertexShader ShaderSources, layout []InputDesc) (InputLayout, error)
+
+	DepthFunc(f DepthFunc)
+	ClearDepth(d float32)
+	Clear(r, g, b, a float32)
+	Viewport(x, y, width, height int)
+	DrawArrays(mode DrawMode, off, count int)
+	DrawElements(mode DrawMode, off, count int)
+	SetBlend(enable bool)
+	SetDepthTest(enable bool)
+	DepthMask(mask bool)
+	BlendFunc(sfactor, dfactor BlendFactor)
+
+	BindInputLayout(i InputLayout)
+	BindProgram(p Program)
+	BindFramebuffer(f Framebuffer)
+	BindTexture(unit int, t Texture)
+	BindVertexBuffer(b Buffer, stride, offset int)
+	BindIndexBuffer(b Buffer)
+	BindImageTexture(unit int, texture Texture, access AccessBits, format TextureFormat)
+
+	MemoryBarrier()
+	DispatchCompute(x, y, z int)
+
+	Release()
+}
+
+type ShaderSources struct {
+	Name           string
+	GLSL100ES      string
+	GLSL300ES      string
+	GLSL310ES      string
+	GLSL130        string
+	GLSL150        string
+	HLSL           []byte
+	Uniforms       UniformsReflection
+	Inputs         []InputLocation
+	Textures       []TextureBinding
+	StorageBuffers []StorageBufferBinding
+}
+
+type StorageBufferBinding struct {
+	Binding   int
+	BlockSize int
+}
+
+type UniformsReflection struct {
+	Blocks    []UniformBlock
+	Locations []UniformLocation
+	Size      int
+}
+
+type TextureBinding struct {
+	Name    string
+	Binding int
+}
+
+type UniformBlock struct {
+	Name    string
+	Binding int
+}
+
+type UniformLocation struct {
+	Name   string
+	Type   DataType
+	Size   int
+	Offset int
+}
+
+type InputLocation struct {
+	// For GLSL.
+	Name     string
+	Location int
+	// For HLSL.
+	Semantic      string
+	SemanticIndex int
+
+	Type DataType
+	Size int
+}
+
+// InputDesc describes a vertex attribute as laid out in a Buffer.
+type InputDesc struct {
+	Type DataType
+	Size int
+
+	Offset int
+}
+
+// InputLayout is the backend specific representation of the mapping
+// between Buffers and shader attributes.
+type InputLayout interface {
+	Release()
+}
+
+type AccessBits uint8
+
+type BlendFactor uint8
+
+type DrawMode uint8
+
+type TextureFilter uint8
+type TextureFormat uint8
+
+type BufferBinding uint8
+
+type DataType uint8
+
+type DepthFunc uint8
+
+type Features uint
+
+type Caps struct {
+	Features       Features
+	MaxTextureSize int
+}
+
+type Program interface {
+	Release()
+	SetStorageBuffer(binding int, buf Buffer)
+	SetVertexUniforms(buf Buffer)
+	SetFragmentUniforms(buf Buffer)
+}
+
+type Buffer interface {
+	Release()
+	Upload(data []byte)
+	Download(data []byte) error
+}
+
+type Framebuffer interface {
+	Invalidate()
+	Release()
+	ReadPixels(src image.Rectangle, pixels []byte) error
+}
+
+type Timer interface {
+	Begin()
+	End()
+	Duration() (time.Duration, bool)
+	Release()
+}
+
+type Texture interface {
+	Upload(offset, size image.Point, pixels []byte)
+	Release()
+}
+
+const (
+	DepthFuncGreater DepthFunc = iota
+	DepthFuncGreaterEqual
+)
+
+const (
+	DataTypeFloat DataType = iota
+	DataTypeInt
+	DataTypeShort
+)
+
+const (
+	BufferBindingIndices BufferBinding = 1 << iota
+	BufferBindingVertices
+	BufferBindingUniforms
+	BufferBindingTexture
+	BufferBindingFramebuffer
+	BufferBindingShaderStorage
+)
+
+const (
+	TextureFormatSRGB TextureFormat = iota
+	TextureFormatFloat
+	TextureFormatRGBA8
+)
+
+const (
+	AccessRead AccessBits = 1 + iota
+	AccessWrite
+)
+
+const (
+	FilterNearest TextureFilter = iota
+	FilterLinear
+)
+
+const (
+	FeatureTimers Features = 1 << iota
+	FeatureFloatRenderTargets
+	FeatureCompute
+)
+
+const (
+	DrawModeTriangleStrip DrawMode = iota
+	DrawModeTriangles
+)
+
+const (
+	BlendFactorOne BlendFactor = iota
+	BlendFactorOneMinusSrcAlpha
+	BlendFactorZero
+	BlendFactorDstColor
+)
+
+var ErrContentLost = errors.New("buffer content lost")
+
+func (f Features) Has(feats Features) bool {
+	return f&feats == feats
+}
+
+func UploadImage(t Texture, offset image.Point, img *image.RGBA) {
+	var pixels []byte
+	size := img.Bounds().Size()
+	if img.Stride != size.X*4 {
+		panic("unsupported stride")
+	}
+	start := img.PixOffset(0, 0)
+	end := img.PixOffset(size.X, size.Y-1)
+	pixels = img.Pix[start:end]
+	t.Upload(offset, size, pixels)
+}