Drawing triangles using fixed function pipelines

main.go

@@ -39,7 +39,7 @@ func main() {
 	defer sdl.GLDeleteContext(glCtx)
 
 	initOpenGL()
-	shaders.LoadShaders()
+	loadShaders()
 
 	//Game loop
 	for isRunning {
@@ -67,11 +67,34 @@ func initOpenGL() {
 	sdl.GLSetAttribute(sdl.GL_BLUE_SIZE, 8)
 
 	sdl.GLSetAttribute(sdl.GL_DOUBLEBUFFER, 1)
+	gl.ClearColor(0, 0, 0, 1)
 
 	sdl.GLSetAttribute(sdl.GL_CONTEXT_PROFILE_MASK, sdl.GL_CONTEXT_PROFILE_COMPATIBILITY)
 	// sdl.GLSetAttribute(sdl.GL_CONTEXT_PROFILE_MASK, sdl.GL_CONTEXT_PROFILE_CORE)
 }
 
+func loadShaders() {
+
+	simpleShader, err := shaders.NewShaderProgram()
+	if err != nil {
+		logging.ErrLog.Fatalln("Failed to create new shader program. Err: ", err)
+	}
+
+	vertShader, err := shaders.LoadAndCompilerShader("./res/shaders/simple.vert.glsl", shaders.VertexShaderType)
+	if err != nil {
+		logging.ErrLog.Fatalln("Failed to create new shader. Err: ", err)
+	}
+
+	fragShader, err := shaders.LoadAndCompilerShader("./res/shaders/simple.frag.glsl", shaders.FragmentShaderType)
+	if err != nil {
+		logging.ErrLog.Fatalln("Failed to create new shader. Err: ", err)
+	}
+
+	simpleShader.AttachShader(vertShader)
+	simpleShader.AttachShader(fragShader)
+	simpleShader.Link()
+}
+
 func handleInputs() {
 
 	input.EventLoopStart()
@@ -95,4 +118,20 @@ func runGameLogic() {
 }
 
 func draw() {
+
+	gl.Clear(gl.COLOR_BUFFER_BIT)
+
+	gl.Begin(gl.TRIANGLES)
+
+	gl.Vertex3f(-0.5, 0.5, 0)
+	gl.Vertex3f(0.5, 0.5, 0)
+	gl.Vertex3f(-0.5, -0.5, 0)
+
+	gl.Vertex3f(0.5, 0.5, 0)
+	gl.Vertex3f(0.5, -0.5, 0)
+	gl.Vertex3f(-0.5, -0.5, 0)
+
+	gl.End()
+
+	window.GLSwap()
 }

shaders/shader_types.go

@@ -0,0 +1,10 @@
+package shaders
+
+import "github.com/go-gl/gl/v4.6-compatibility/gl"
+
+type ShaderType int
+
+const (
+	VertexShaderType   ShaderType = gl.VERTEX_SHADER
+	FragmentShaderType ShaderType = gl.FRAGMENT_SHADER
+)

shaders/shaders.go

@@ -1,6 +1,7 @@
 package shaders
 
 import (
+	"errors"
 	"os"
 	"strings"
 
@@ -8,58 +9,94 @@ import (
 	"github.com/go-gl/gl/v4.6-compatibility/gl"
 )
 
+type Shader struct {
+	ID         uint32
+	ShaderType ShaderType
+}
+
+func (s Shader) Delete() {
+	gl.DeleteShader(s.ID)
+}
+
 type ShaderProgram struct {
 	ID           uint32
 	VertShaderID uint32
 	FragShaderID uint32
 }
 
-func LoadShaders() {
+func (sp *ShaderProgram) AttachShader(shader Shader) {
 
-	vertShaderText, err := os.ReadFile("./res/shaders/simple.vert.glsl")
+	gl.AttachShader(sp.ID, shader.ID)
+	switch shader.ShaderType {
+	case VertexShaderType:
+		sp.VertShaderID = shader.ID
+	case FragmentShaderType:
+		sp.FragShaderID = shader.ID
+	default:
+		logging.ErrLog.Println("Unknown shader type ", shader.ShaderType, " for ID ", shader.ID)
+	}
+}
+
+func (sp *ShaderProgram) Link() {
+
+	gl.LinkProgram(sp.ID)
+
+	if sp.VertShaderID != 0 {
+		gl.DeleteShader(sp.VertShaderID)
+	}
+	if sp.FragShaderID != 0 {
+		gl.DeleteShader(sp.FragShaderID)
+	}
+}
+
+func (sp *ShaderProgram) Delete() {
+	gl.DeleteProgram(sp.ID)
+}
+
+func NewShaderProgram() (ShaderProgram, error) {
+
+	id := gl.CreateProgram()
+	if id == 0 {
+		return ShaderProgram{}, errors.New("failed to create shader program")
+	}
+
+	return ShaderProgram{ID: id}, nil
+}
+
+func LoadAndCompilerShader(shaderPath string, shaderType ShaderType) (Shader, error) {
+
+	shaderSource, err := os.ReadFile(shaderPath)
 	if err != nil {
-		logging.ErrLog.Fatalln("Failed to read vertex shader. Err: ", err)
+		logging.ErrLog.Println("Failed to read shader. Err: ", err)
+		return Shader{}, err
 	}
 
-	fragShaderText, err := os.ReadFile("./res/shaders/simple.frag.glsl")
+	shaderID := gl.CreateShader(uint32(shaderType))
-	if err != nil {
+	if shaderID == 0 {
-		logging.ErrLog.Fatalln("Failed to read fragment shader. Err: ", err)
+		logging.ErrLog.Println("Failed to create shader.")
+		return Shader{}, errors.New("failed to create shader")
 	}
 
-	shader := &ShaderProgram{}
+	//Load shader source and compile
-	shader.ID = gl.CreateProgram()
+	shaderCStr, shaderFree := gl.Strs(string(shaderSource) + "\x00")
-	if shader.ID == 0 {
+	defer shaderFree()
-		logging.ErrLog.Fatalln("Failed to create shader program")
+	gl.ShaderSource(shaderID, 1, shaderCStr, nil)
+
+	gl.CompileShader(shaderID)
+	if err := getShaderCompileErrors(shaderID); err != nil {
+		gl.DeleteShader(shaderID)
+		return Shader{}, err
 	}
 
-	shader.VertShaderID = gl.CreateShader(gl.VERTEX_SHADER)
+	return Shader{ID: shaderID, ShaderType: shaderType}, nil
-	shader.FragShaderID = gl.CreateShader(gl.FRAGMENT_SHADER)
-
-	vertexCStr, vertFree := gl.Strs(string(vertShaderText) + "\x00")
-	defer vertFree()
-	gl.ShaderSource(shader.VertShaderID, 1, vertexCStr, nil)
-
-	fragCStr, fragFree := gl.Strs(string(fragShaderText) + "\x00")
-	defer fragFree()
-	gl.ShaderSource(shader.FragShaderID, 1, fragCStr, nil)
-
-	gl.CompileShader(shader.VertShaderID)
-	getShaderCompileErrors(shader.VertShaderID)
-
-	gl.CompileShader(shader.FragShaderID)
-	getShaderCompileErrors(shader.FragShaderID)
-
-	gl.AttachShader(shader.ID, shader.VertShaderID)
-	gl.AttachShader(shader.ID, shader.FragShaderID)
-	gl.LinkProgram(shader.ID)
 }
 
-func getShaderCompileErrors(shaderID uint32) {
+func getShaderCompileErrors(shaderID uint32) error {
 
 	var compiledSuccessfully int32
 	gl.GetShaderiv(shaderID, gl.COMPILE_STATUS, &compiledSuccessfully)
 	if compiledSuccessfully == gl.TRUE {
-		return
+		return nil
 	}
 
 	var logLength int32
@@ -69,5 +106,6 @@ func getShaderCompileErrors(shaderID uint32) {
 	gl.GetShaderInfoLog(shaderID, logLength, nil, log)
 
 	errMsg := gl.GoStr(log)
-	println("Compilation of shader with id ", shaderID, " failed. Err: ", errMsg)
+	logging.ErrLog.Println("Compilation of shader with id ", shaderID, " failed. Err: ", errMsg)
+	return errors.New(errMsg)
 }