add hellotriangle for opengl 4.6

Author: soypat

gl46core-hellotriangle/main.go

@@ -0,0 +1,178 @@
+// Copyright 2021 The go-gl Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Renders a red triangle using GLFW 3.3 and OpenGL 4.6 core forward-compatible profile.
+package main
+
+import (
+	"errors"
+	"fmt"
+	_ "image/png"
+	"log"
+	"runtime"
+
+	"github.com/go-gl/gl/v4.6-core/gl"
+	"github.com/go-gl/glfw/v3.3/glfw"
+)
+
+const windowWidth = 800
+const windowHeight = 600
+
+func init() {
+	// GLFW event handling must run on the main OS thread
+	runtime.LockOSThread()
+}
+
+func main() {
+	if err := glfw.Init(); err != nil {
+		log.Fatalln("failed to initialize glfw:", err)
+	}
+	defer glfw.Terminate()
+
+	glfw.WindowHint(glfw.Resizable, glfw.False)
+	glfw.WindowHint(glfw.ContextVersionMajor, 4)
+	glfw.WindowHint(glfw.ContextVersionMinor, 1)
+	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
+	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
+	window, err := glfw.CreateWindow(windowWidth, windowHeight, "Hello colorful triangle", nil, nil)
+	if err != nil {
+		panic(err)
+	}
+	window.MakeContextCurrent()
+
+	// Initialize Glow.
+	if err := gl.Init(); err != nil {
+		panic(err)
+	}
+
+	version := gl.GoStr(gl.GetString(gl.VERSION))
+	fmt.Println("OpenGL version", version)
+
+	// Compile, link and validate vertex and fragment shaders.
+	program, err := CompileProgram(vertexShader, fragmentShader)
+	if err != nil {
+		panic(err)
+	}
+	gl.UseProgram(program)
+	gl.BindFragDataLocation(program, 0, gl.Str("outputColor\x00"))
+
+	// Configure the vertex data
+	var vao uint32
+	gl.GenVertexArrays(1, &vao)
+	gl.BindVertexArray(vao)
+
+	// float32 is 4 bytes wide.
+	const attrSize = 4
+	var vbo uint32
+	gl.GenBuffers(1, &vbo)
+	gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
+	gl.BufferData(gl.ARRAY_BUFFER, attrSize*len(triangleVertices), gl.Ptr(triangleVertices), gl.STATIC_DRAW)
+	vertAttrib := uint32(gl.GetAttribLocation(program, gl.Str("vert\x00")))
+	gl.EnableVertexAttribArray(vertAttrib)
+
+	// Stride is 2 since our data is 2D.
+	gl.VertexAttribPointerWithOffset(vertAttrib, 3, gl.FLOAT, false, 2*attrSize, 0)
+
+	for !window.ShouldClose() {
+		gl.Clear(gl.COLOR_BUFFER_BIT)
+		// gl.UniformMatrix4fv(modelUniform, 1, false, &model[0])
+		gl.BindVertexArray(vao)
+		gl.DrawArrays(gl.TRIANGLES, 0, 3)
+		// Maintenance
+		window.SwapBuffers()
+		glfw.PollEvents()
+		if window.GetKey(glfw.KeyEscape) == glfw.Press {
+			window.SetShouldClose(true)
+		}
+	}
+}
+
+var vertexShader string = `
+#version 330
+in vec3 vert;
+
+void main() {
+	gl_Position = vec4(vert,1);
+}
+` + "\x00"
+
+var fragmentShader string = `
+#version 330
+out vec4 outputColor;
+
+void main() {
+	outputColor = vec4(1.0,0.0,0.0,1.0);
+}
+` + "\x00"
+
+var triangleVertices = []float32{
+	-1.0, -1.0,
+	1.0, -1.0,
+	0.0, 1.0,
+}
+
+func CompileProgram(vertexSrcCode, fragmentSrcCode string) (program uint32, err error) {
+	program = gl.CreateProgram()
+	vid, err := compile(gl.VERTEX_SHADER, vertexSrcCode)
+	if err != nil {
+		return 0, fmt.Errorf("vertex shader compile: %w", err)
+	}
+	fid, err := compile(gl.FRAGMENT_SHADER, fragmentSrcCode)
+	if err != nil {
+		return 0, fmt.Errorf("fragment shader compile: %w", err)
+	}
+	gl.AttachShader(program, vid)
+	gl.AttachShader(program, fid)
+	gl.LinkProgram(program)
+	log := ivLog(program, gl.LINK_STATUS, gl.GetProgramiv, gl.GetProgramInfoLog)
+	if len(log) > 0 {
+		return 0, fmt.Errorf("link failed: %v", log)
+	}
+	// We should technically call DetachShader after linking... https://www.youtube.com/watch?v=71BLZwRGUJE&list=PLlrATfBNZ98foTJPJ_Ev03o2oq3-GGOS2&index=7&ab_channel=TheCherno
+	gl.ValidateProgram(program)
+	log = ivLog(program, gl.VALIDATE_STATUS, gl.GetProgramiv, gl.GetProgramInfoLog)
+	if len(log) > 0 {
+		return 0, fmt.Errorf("validation failed: %v", log)
+	}
+
+	// We can clean up.
+	gl.DeleteShader(vid)
+	gl.DeleteShader(fid)
+	return program, nil
+}
+
+func compile(shaderType uint32, sourceCode string) (uint32, error) {
+	id := gl.CreateShader(shaderType)
+	csources, free := gl.Strs(sourceCode)
+	gl.ShaderSource(id, 1, csources, nil)
+	free()
+	gl.CompileShader(id)
+
+	// We now check the errors during compile, if there were any.
+	log := ivLog(id, gl.COMPILE_STATUS, gl.GetShaderiv, gl.GetShaderInfoLog)
+	if len(log) > 0 {
+		return 0, errors.New(log)
+	}
+	return id, nil
+}
+
+// ivLog is a helper function for extracting log data
+// from a Shader compilation step or program linking.
+//
+//	log := ivLog(id, gl.COMPILE_STATUS, gl.GetShaderiv, gl.GetShaderInfoLog)
+//	if len(log) > 0 {
+//		return 0, errors.New(log)
+//	}
+func ivLog(id, plName uint32, getIV func(program uint32, pname uint32, params *int32), getInfo func(program uint32, bufSize int32, length *int32, infoLog *uint8)) string {
+	var iv int32
+	getIV(id, plName, &iv)
+	if iv == gl.FALSE {
+		var logLength int32
+		getIV(id, gl.INFO_LOG_LENGTH, &logLength)
+		log := make([]byte, logLength)
+		getInfo(id, logLength, &logLength, &log[0])
+		return string(log[:len(log)-1]) // we exclude the last null character.
+	}
+	return ""
+}