gl

package

v2.4.0-rc1 Latest Latest Go to latest Published: Aug 25, 2023 License: BSD-3-Clause Imports: 5 Imported by: 0

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github.com/fyne-io/fyne

Documentation ¶

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Overview ¶

Package gl implements Go bindings for OpenGL ES 2.0 and ES 3.0.

The GL functions are defined on a Context object that is responsible for tracking a GL context. Typically a windowing system package (such as golang.org/x/exp/shiny/screen) will call NewContext and provide a gl.Context for a user application.

If the gl package is compiled on a platform capable of supporting ES 3.0, the gl.Context object also implements gl.Context3.

The bindings are deliberately minimal, staying as close the C API as possible. The semantics of each function maps onto functions described in the Khronos documentation:

https://www.khronos.org/opengles/sdk/docs/man/

One notable departure from the C API is the introduction of types to represent common uses of GLint: Texture, Surface, Buffer, etc.

Constants ¶

View Source

const (
	False            = 0
	True             = 1
	One              = 1
	Triangles        = 0x0004
	TriangleStrip    = 0x0005
	SrcAlpha         = 0x0302
	OneMinusSrcAlpha = 0x0303
	Front            = 0x0404
	DepthTest        = 0x0B71
	Blend            = 0x0BE2
	ScissorTest      = 0x0C11
	Texture2D        = 0x0DE1

	UnsignedByte = 0x1401
	Float        = 0x1406
	RED          = 0x1903
	RGBA         = 0x1908

	Nearest          = 0x2600
	Linear           = 0x2601
	TextureMagFilter = 0x2800
	TextureMinFilter = 0x2801
	TextureWrapS     = 0x2802
	TextureWrapT     = 0x2803

	ConstantAlpha            = 0x8003
	OneMinusConstantAlpha    = 0x8004
	ClampToEdge              = 0x812F
	Texture0                 = 0x84C0
	StaticDraw               = 0x88E4
	DynamicDraw              = 0x88E8
	FragmentShader           = 0x8B30
	VertexShader             = 0x8B31
	AttachedShaders          = 0x8B85
	ActiveUniformMaxLength   = 0x8B87
	ActiveAttributeMaxLength = 0x8B8A
	ArrayBuffer              = 0x8892
	CompileStatus            = 0x8B81
	LinkStatus               = 0x8B82
	InfoLogLength            = 0x8B84
	ShaderSourceLength       = 0x8B88

	DepthBufferBit = 0x00000100
	ColorBufferBit = 0x00004000
)

Contains Khronos OpenGL API specification constants.

Variables ¶

This section is empty.

Functions ¶

func NewContext ¶

func NewContext() (Context, Worker)

NewContext creates a cgo OpenGL context.

See the Worker interface for more details on how it is used.

func Version ¶

func Version() string

Version returns a GL ES version string, either "GL_ES_2_0" or "GL_ES_3_0". Future versions of the gl package may return "GL_ES_3_1".

Types ¶

type Attrib ¶

type Attrib struct {
	Value uint
}

Attrib identifies the location of a specific attribute variable.

func (Attrib) String ¶

func (v Attrib) String() string

type Buffer ¶

type Buffer struct {
	Value uint32
}

Buffer identifies a GL buffer object.

func (Buffer) String ¶

func (v Buffer) String() string

type Context ¶

type Context interface {
	// ActiveTexture sets the active texture unit.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glActiveTexture.xhtml
	ActiveTexture(texture Enum)

	// AttachShader attaches a shader to a program.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glAttachShader.xhtml
	AttachShader(p Program, s Shader)

	// BindBuffer binds a buffer.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glBindBuffer.xhtml
	BindBuffer(target Enum, b Buffer)
	// BindTexture binds a texture.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glBindTexture.xhtml
	BindTexture(target Enum, t Texture)

	// BindVertexArray binds a vertex array.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glBindVertexArray.xhtml
	BindVertexArray(rb VertexArray)

	// BlendColor sets the blend color.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glBlendColor.xhtml
	BlendColor(red, green, blue, alpha float32)

	// BlendFunc sets the pixel blending factors.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glBlendFunc.xhtml
	BlendFunc(sfactor, dfactor Enum)

	// BufferData creates a new data store for the bound buffer object.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glBufferData.xhtml
	BufferData(target Enum, src []byte, usage Enum)
	// Clear clears the window.
	//
	// The behavior of Clear is influenced by the pixel ownership test,
	// the scissor test, dithering, and the buffer writemasks.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glClear.xhtml
	Clear(mask Enum)

	// ClearColor specifies the RGBA values used to clear color buffers.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glClearColor.xhtml
	ClearColor(red, green, blue, alpha float32)

	// CompileShader compiles the source code of s.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glCompileShader.xhtml
	CompileShader(s Shader)

	// CreateBuffer creates a buffer object.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGenBuffers.xhtml
	CreateBuffer() Buffer

	// CreateProgram creates a new empty program object.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glCreateProgram.xhtml
	CreateProgram() Program

	// CreateShader creates a new empty shader object.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glCreateShader.xhtml
	CreateShader(ty Enum) Shader

	// CreateTexture creates a texture object.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGenTextures.xhtml
	CreateTexture() Texture

	// CreateTVertexArray creates a vertex array.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGenVertexArrays.xhtml
	CreateVertexArray() VertexArray
	// DeleteBuffer deletes the given buffer object.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glDeleteBuffers.xhtml
	DeleteBuffer(v Buffer)

	// DeleteTexture deletes the given texture object.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glDeleteTextures.xhtml
	DeleteTexture(v Texture)

	// Disable disables various GL capabilities.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glDisable.xhtml
	Disable(cap Enum)

	// DrawArrays renders geometric primitives from the bound data.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glDrawArrays.xhtml
	DrawArrays(mode Enum, first, count int)

	// Enable enables various GL capabilities.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glEnable.xhtml
	Enable(cap Enum)

	// EnableVertexAttribArray enables a vertex attribute array.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glEnableVertexAttribArray.xhtml
	EnableVertexAttribArray(a Attrib)
	// Flush empties all buffers. It does not block.
	//
	// An OpenGL implementation may buffer network communication,
	// the command stream, or data inside the graphics accelerator.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glFlush.xhtml
	Flush()

	// GetAttribLocation returns the location of an attribute variable.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGetAttribLocation.xhtml
	GetAttribLocation(p Program, name string) Attrib

	// GetError returns the next error.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGetError.xhtml
	GetError() Enum

	// GetProgrami returns a parameter value for a shader.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGetProgramiv.xhtml
	GetProgrami(p Program, pname Enum) int

	// GetProgramInfoLog returns the information log for a shader.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGetProgramInfoLog.xhtml
	GetProgramInfoLog(p Program) string

	// GetShaderi returns a parameter value for a shader.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGetShaderiv.xhtml
	GetShaderi(s Shader, pname Enum) int

	// GetShaderInfoLog returns the information log for a shader.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGetShaderInfoLog.xhtml
	GetShaderInfoLog(s Shader) string

	// GetUniformLocation returns the location of a uniform variable.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glGetUniformLocation.xhtml
	GetUniformLocation(p Program, name string) Uniform

	// LinkProgram links the specified program.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glLinkProgram.xhtml
	LinkProgram(p Program)

	// ReadPixels returns pixel data from a buffer.
	//
	// In GLES 3, the source buffer is controlled with ReadBuffer.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glReadPixels.xhtml
	ReadPixels(dst []byte, x, y, width, height int, format, ty Enum)

	// Scissor defines the scissor box rectangle, in window coordinates.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glScissor.xhtml
	Scissor(x, y, width, height int32)

	// ShaderSource sets the source code of s to the given source code.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glShaderSource.xhtml
	ShaderSource(s Shader, src string)
	// TexImage2D writes a 2D texture image.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glTexImage2D.xhtml
	TexImage2D(target Enum, level int, internalFormat int, width, height int, format Enum, ty Enum, data []byte)

	// TexParameteri sets an integer texture parameter.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glTexParameter.xhtml
	TexParameteri(target, pname Enum, param int)

	// Uniform1f writes a float uniform variable.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glUniform.xhtml
	Uniform1f(dst Uniform, v float32)

	// Uniform2f writes a vec2 uniform variable.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glUniform.xhtml
	Uniform2f(dst Uniform, v0, v1 float32)

	// Uniform4f writes a vec4 uniform variable.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glUniform.xhtml
	Uniform4f(dst Uniform, v0, v1, v2, v3 float32)

	// Uniform4fv writes a vec4 uniform array of len(src)/4 elements.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glUniform.xhtml
	Uniform4fv(dst Uniform, src []float32)

	// UseProgram sets the active program.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glUseProgram.xhtml
	UseProgram(p Program)

	// VertexAttribPointer uses a bound buffer to define vertex attribute data.
	//
	// Direct use of VertexAttribPointer to load data into OpenGL is not
	// supported via the Go bindings. Instead, use BindBuffer with an
	// ARRAY_BUFFER and then fill it using BufferData.
	//
	// The size argument specifies the number of components per attribute,
	// between 1-4. The stride argument specifies the byte offset between
	// consecutive vertex attributes.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glVertexAttribPointer.xhtml
	VertexAttribPointer(dst Attrib, size int, ty Enum, normalized bool, stride, offset int)

	// Viewport sets the viewport, an affine transformation that
	// normalizes device coordinates to window coordinates.
	//
	// http://www.khronos.org/opengles/sdk/docs/man3/html/glViewport.xhtml
	Viewport(x, y, width, height int)
}

Context is an OpenGL ES context.

A Context has a method for every GL function supported by ES 2 or later. In a program compiled with ES 3 support.

Calls are not safe for concurrent use. However calls can be made from any goroutine, the gl package removes the notion of thread-local context.

Contexts are independent. Two contexts can be used concurrently.

type Enum ¶

type Enum uint32

Enum is equivalent to GLenum, and is normally used with one of the constants defined in this package.

type Framebuffer ¶

type Framebuffer struct {
	Value uint32
}

Framebuffer identifies a GL framebuffer.

func (Framebuffer) String ¶

func (v Framebuffer) String() string

type Program ¶

type Program struct {
	// Init is set by CreateProgram, as some GL drivers (in particular,
	// ANGLE) return true for glIsProgram(0).
	Init  bool
	Value uint32
}

Program identifies a compiled shader program.

func (Program) String ¶

func (v Program) String() string

type Renderbuffer ¶

type Renderbuffer struct {
	Value uint32
}

A Renderbuffer is a GL object that holds an image in an internal format.

func (Renderbuffer) String ¶

func (v Renderbuffer) String() string

type Shader ¶

type Shader struct {
	Value uint32
}

Shader identifies a GLSL shader.

func (Shader) String ¶

func (v Shader) String() string

type Texture ¶

type Texture struct {
	Value uint32
}

A Texture identifies a GL texture unit.

func (Texture) String ¶

func (v Texture) String() string

type Uniform ¶

type Uniform struct {
	Value int32
}

Uniform identifies the location of a specific uniform variable.

func (Uniform) String ¶

func (v Uniform) String() string

type VertexArray ¶

type VertexArray struct {
	Value uint32
}

A VertexArray is a GL object that holds vertices in an internal format.

func (VertexArray) String ¶

func (v VertexArray) String() string

type Worker ¶

type Worker interface {
	// WorkAvailable returns a channel that communicates when DoWork should be
	// called.
	WorkAvailable() <-chan struct{}

	// DoWork performs any pending OpenGL calls.
	DoWork()
}

Worker is used by display driver code to execute OpenGL calls.

Typically display driver code creates a gl.Context for an application, and along with it establishes a locked OS thread to execute the cgo calls:

go func() {
	runtime.LockOSThread()
	// ... platform-specific cgo call to bind a C OpenGL context
	// into thread-local storage.

	glctx, worker := gl.NewContext()
	workAvailable := worker.WorkAvailable()
	go userAppCode(glctx)
	for {
		select {
		case <-workAvailable:
			worker.DoWork()
		case <-drawEvent:
			// ... platform-specific cgo call to draw screen
		}
	}
}()

This interface is an internal implementation detail and should only be used by the package responsible for managing the screen.

Source Files ¶

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