gistfile1.go

package main

import (
	"github.com/go-gl/gl"
	glfw "github.com/go-gl/glfw3"
	"log"
	"runtime"
)

var (
	program gl.Program
)

func initShaders() {
	shaders := []struct {
		stype  gl.GLenum
		source string
	}{
		{gl.VERTEX_SHADER, vertex_shader},
		{gl.FRAGMENT_SHADER, fragment_shader},
	}

	program = gl.CreateProgram()
	for i, shaderDescriptor := range shaders {
		shader := gl.CreateShader(shaderDescriptor.stype)
		defer shader.Delete()
		shader.Source(shaderDescriptor.source)
		shader.Compile()
		if shader.Get(gl.COMPILE_STATUS) != gl.TRUE {
			log.Panicf("shader[%d] error: %v", i, shader.GetInfoLog())
		}
		program.AttachShader(shader)
	}
	program.Link()
	if program.Get(gl.LINK_STATUS) != gl.TRUE {
		log.Panic("linker error: " + program.GetInfoLog())
	}
	program.Use()
}

func initGL() {
	gl.Init()
	initShaders()

	gl.ClearColor(0, 0, 0.4, 1)

	vertices := []float32{
		-1.0, -1.0,
		1.0, -1.0,
		0.0, 1.0,
	}

	vertexArray := gl.GenVertexArray()
	vertexArray.Bind()
	buf := gl.GenBuffer()
	buf.Bind(gl.ARRAY_BUFFER)
	gl.BufferData(gl.ARRAY_BUFFER, 4 * len(vertices), vertices, gl.STATIC_DRAW)

	attr := program.GetAttribLocation("position")
	attr.EnableArray()
	buf.Bind(gl.ARRAY_BUFFER)
	attr.AttribPointer(2, gl.FLOAT, false, 0, nil)
}

func draw() {
	gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
	gl.DrawArrays(gl.TRIANGLES, 0, 3)
}

func keys(window *glfw.Window, k glfw.Key, s int, action glfw.Action, mods glfw.ModifierKey) {
	if action == glfw.Press && glfw.Key(k) == glfw.KeyEscape {
		window.SetShouldClose(true)
	}
}

func errorCallback(err glfw.ErrorCode, desc string) {
	log.Printf("%v: %v\n", err, desc)
}

func main() {
	runtime.LockOSThread()
	glfw.SetErrorCallback(errorCallback)
	if !glfw.Init() {
		panic("Failed to initialize GLFW")
	}
	defer glfw.Terminate()

	glfw.WindowHint(glfw.ContextVersionMajor, 3)
	glfw.WindowHint(glfw.ContextVersionMinor, 3)
	glfw.WindowHint(glfw.OpenglProfile, glfw.OpenglCoreProfile)
	glfw.WindowHint(glfw.Resizable, 0)

	window, err := glfw.CreateWindow(1024, 768, "test", nil, nil)
	if err != nil {
		log.Panic(err)
	}
	defer window.Destroy()
	window.SetKeyCallback(keys)
	window.MakeContextCurrent()

	initGL()

	for !window.ShouldClose() {
		draw()
		window.SwapBuffers()
		glfw.PollEvents()
	}
}

const vertex_shader = `
#version 330 core

in vec4 position;

void main()
{
	gl_Position = position;
}
`

const fragment_shader = `
#version 330 core

out vec3 color;

void main()
{
	color = vec3(1, 0, 0);
}
`