Add proxy package for building different GL versions

Makefile

@@ -1,13 +1,23 @@
 
+ifeq ($(shell uname),Darwin)
+GL_VER:=v4.1-core
+else
+GL_VER:=v2.1
+endif
+
 all: wolfengo test
 
-wolfengo:
+wolfengo: gl
 	go build -o bin/wolfengo ./src
 
+gl:
+	go run src/gl/generate/generate.go $(GL_VER) > src/gl/gl.go
+	gofmt -w src/gl/gl.go
+
 errcheck:
 	errcheck ./src
 
 test:
 	go test ./src
 
-.PHONY: all wolfengo test errcheck
+.PHONY: all wolfengo test errcheck gl

src/gl/generate/generate.go

@@ -0,0 +1,133 @@
+// +build generate
+/*
+WolfenGo - https://github.com/gdm85/wolfengo
+Copyright (C) 2016~2019 gdm85
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+func main() {
+	glVer := os.Args[1]
+
+	parts := strings.Split(glVer, ".")
+	major, minor := parts[0][1:], parts[1]
+
+	// remove '-core'
+	minor = strings.Replace(minor, "-core", "", 1)
+
+	fmt.Printf(`// Code generated by src/gl/generate/generate.go DO NOT EDIT
+package gl
+
+import "github.com/go-gl/gl/%s/gl"
+
+const (
+	RequestedContextVersionMajor = %s
+	RequestedContextVersionMinor = %s
+)
+
+const (
+	VERTEX_SHADER        = gl.VERTEX_SHADER
+	FRAGMENT_SHADER      = gl.FRAGMENT_SHADER
+	DEBUG_SEVERITY_HIGH  = gl.DEBUG_SEVERITY_HIGH
+	VERSION              = gl.VERSION
+	DEBUG_OUTPUT         = gl.DEBUG_OUTPUT
+	CW                   = gl.CW
+	BACK                 = gl.BACK
+	CULL_FACE            = gl.CULL_FACE
+	DEPTH_TEST           = gl.DEPTH_TEST
+	BLEND                = gl.BLEND
+	SRC_ALPHA            = gl.SRC_ALPHA
+	ONE_MINUS_SRC_ALPHA  = gl.ONE_MINUS_SRC_ALPHA
+	DEPTH_CLAMP          = gl.DEPTH_CLAMP
+	TEXTURE_2D           = gl.TEXTURE_2D
+	COLOR_BUFFER_BIT     = gl.COLOR_BUFFER_BIT
+	DEPTH_BUFFER_BIT     = gl.DEPTH_BUFFER_BIT
+	ARRAY_BUFFER         = gl.ARRAY_BUFFER
+	ELEMENT_ARRAY_BUFFER = gl.ELEMENT_ARRAY_BUFFER
+	STATIC_DRAW          = gl.STATIC_DRAW
+	FLOAT                = gl.FLOAT
+	TRIANGLES            = gl.TRIANGLES
+	UNSIGNED_INT         = gl.UNSIGNED_INT
+	INFO_LOG_LENGTH      = gl.INFO_LOG_LENGTH
+	LINK_STATUS          = gl.LINK_STATUS
+	FALSE                = gl.FALSE
+	VALIDATE_STATUS      = gl.VALIDATE_STATUS
+	COMPILE_STATUS       = gl.COMPILE_STATUS
+	TEXTURE_MIN_FILTER   = gl.TEXTURE_MIN_FILTER
+	TEXTURE_WRAP_T       = gl.TEXTURE_WRAP_T
+	REPEAT               = gl.REPEAT
+	TEXTURE_WRAP_S       = gl.TEXTURE_WRAP_S
+	NEAREST              = gl.NEAREST
+	TEXTURE_MAG_FILTER   = gl.TEXTURE_MAG_FILTER
+	RGBA8                = gl.RGBA8
+	RGBA                 = gl.RGBA
+	UNSIGNED_BYTE        = gl.UNSIGNED_BYTE
+)
+
+var (
+	DrawElements             = gl.DrawElements
+	Init                     = gl.Init
+	GoStr                    = gl.GoStr
+	GetString                = gl.GetString
+	DebugMessageCallback     = gl.DebugMessageCallback
+	Enable                   = gl.Enable
+	ClearColor               = gl.ClearColor
+	FrontFace                = gl.FrontFace
+	CullFace                 = gl.CullFace
+	BlendFunc                = gl.BlendFunc
+	Clear                    = gl.Clear
+	GenBuffers               = gl.GenBuffers
+	BindBuffer               = gl.BindBuffer
+	BufferData               = gl.BufferData
+	Ptr                      = gl.Ptr
+	EnableVertexAttribArray  = gl.EnableVertexAttribArray
+	VertexAttribPointer      = gl.VertexAttribPointer
+	PtrOffset                = gl.PtrOffset
+	DisableVertexAttribArray = gl.DisableVertexAttribArray
+	CreateProgram            = gl.CreateProgram
+	UseProgram               = gl.UseProgram
+	Strs                     = gl.Strs
+	GetUniformLocation       = gl.GetUniformLocation
+	GetProgramiv             = gl.GetProgramiv
+	GetProgramInfoLog        = gl.GetProgramInfoLog
+	GetShaderiv              = gl.GetShaderiv
+	GetShaderInfoLog         = gl.GetShaderInfoLog
+	Str                      = gl.Str
+	LinkProgram              = gl.LinkProgram
+	ValidateProgram          = gl.ValidateProgram
+	CreateShader             = gl.CreateShader
+	ShaderSource             = gl.ShaderSource
+	CompileShader            = gl.CompileShader
+	AttachShader             = gl.AttachShader
+	Uniform3f                = gl.Uniform3f
+	UniformMatrix4fv         = gl.UniformMatrix4fv
+	BindTexture              = gl.BindTexture
+	GenTextures              = gl.GenTextures
+	TexParameteri            = gl.TexParameteri
+	TexParameterf            = gl.TexParameterf
+	TexImage2D               = gl.TexImage2D
+	GenVertexArrays          = gl.GenVertexArrays
+	BindVertexArray          = gl.BindVertexArray
+)
+`, glVer, major, minor)
+}

src/level.go

@@ -22,7 +22,7 @@ import (
 	"fmt"
 	"math"
 
-	"github.com/go-gl/gl/v2.1/gl"
+	"github.com/gdm85/wolfengo/src/gl"
 )
 
 const (
@@ -71,11 +71,11 @@ func getBasicShader() (*Shader, error) {
 			return nil, err
 		}
 
-		err = _basicShader.addProgramFromFile("basicVertex120.vs", gl.VERTEX_SHADER)
+		err = _basicShader.addProgramFromFile("basicVertex"+shaderVersion+".vs", gl.VERTEX_SHADER)
 		if err != nil {
 			return nil, err
 		}
-		err = _basicShader.addProgramFromFile("basicFragment120.fs", gl.FRAGMENT_SHADER)
+		err = _basicShader.addProgramFromFile("basicFragment"+shaderVersion+".fs", gl.FRAGMENT_SHADER)
 		if err != nil {
 			return nil, err
 		}

src/main.go

@@ -26,7 +26,7 @@ import (
 	"time"
 	"unsafe"
 
-	"github.com/go-gl/gl/v2.1/gl"
+	"github.com/gdm85/wolfengo/src/gl"
 	"github.com/go-gl/glfw/v3.1/glfw"
 )
 
@@ -72,6 +72,10 @@ func debugCb(
 	fmt.Fprintln(os.Stderr, msg)
 }
 
+// needed for some older hardware e.g. Intel HD graphics
+// notice that this suffix only changes a couple shaders, while the rest uses the 330 version
+var shaderVersion = "120"
+
 func main() {
 	fmt.Printf(`WolfenGo v%s, Copyright (C) 2016~2019 gdm85
 https://github.com/gdm85/wolfengo
@@ -85,8 +89,16 @@ under GNU/GPLv2 license.`+"\n", version)
 	defer glfw.Terminate()
 
 	// create a context and activate it
-	glfw.WindowHint(glfw.ContextVersionMajor, 2)
-	glfw.WindowHint(glfw.ContextVersionMinor, 1)
+	glfw.WindowHint(glfw.ContextVersionMajor, gl.RequestedContextVersionMajor)
+	glfw.WindowHint(glfw.ContextVersionMinor, gl.RequestedContextVersionMinor)
+	if gl.RequestedContextVersionMajor >= 3 {
+		// switch to version 330
+		shaderVersion = ""
+		glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
+		if gl.RequestedContextVersionMajor >= 2 {
+			glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
+		}
+	}
 	glfw.WindowHint(glfw.Resizable, glfw.False)
 	glfw.WindowHint(glfw.DoubleBuffer, glfw.True)
 	var err error

src/mesh.go

@@ -18,7 +18,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 */
 package main
 
-import "github.com/go-gl/gl/v2.1/gl"
+import "github.com/gdm85/wolfengo/src/gl"
 
 type Mesh struct {
 	vbo, ibo uint32

src/shader.go

@@ -24,7 +24,7 @@ import (
 	"io/ioutil"
 	"strings"
 
-	"github.com/go-gl/gl/v2.1/gl"
+	"github.com/gdm85/wolfengo/src/gl"
 )
 
 type Shader struct {
@@ -84,6 +84,10 @@ func (s *Shader) getShaderInfoLog(shader uint32, context string) error {
 }
 
 func (s *Shader) compile() error {
+	var vao uint32
+	gl.GenVertexArrays(1, &vao)
+	gl.BindVertexArray(vao)
+
 	gl.LinkProgram(s.program)
 	var result int32
 	gl.GetProgramiv(s.program, gl.LINK_STATUS, &result)

src/texture.go

@@ -25,7 +25,7 @@ import (
 	_ "image/png"
 	"os"
 
-	"github.com/go-gl/gl/v2.1/gl"
+	"github.com/gdm85/wolfengo/src/gl"
 )
 
 type Texture struct {