Shader handling

shaders/program.go

@@ -0,0 +1,89 @@
+package shaders
+
+import (
+	"fmt"
+	"log"
+	"strings"
+
+	"github.com/go-gl/gl/v4.6-core/gl"
+)
+
+type Program struct {
+	Name    string
+	ID      uint32
+	Shaders []Shader
+}
+
+func NewProgram(name string) Program {
+
+	p := Program{Name: name}
+	p.Shaders = make([]Shader, 0)
+
+	if p.ID = gl.CreateProgram(); p.ID == 0 {
+		log.Fatalln("Creating OpenGL program failed")
+	}
+
+	return p
+}
+
+//AttachShader adds the shader to list of shaders and attaches it in opengl
+func (p *Program) AttachShader(s Shader) {
+
+	p.Shaders = append(p.Shaders, s)
+	gl.AttachShader(p.ID, s.ID)
+}
+
+//DetachShader removes the shader from the list of shaders and detaches it in opengl
+func (p *Program) DetachShader(s Shader) {
+
+	//To remove a shader we move the last shader to its place, then shrink the slice by one
+	for i := 0; i < len(p.Shaders); i++ {
+
+		if p.Shaders[i].ID != s.ID {
+			continue
+		}
+
+		gl.DetachShader(p.ID, s.ID)
+
+		p.Shaders[i] = p.Shaders[len(p.Shaders)-1]
+		p.Shaders = p.Shaders[:len(p.Shaders)-1]
+		return
+	}
+}
+
+func (p *Program) Link() error {
+
+	gl.LinkProgram(p.ID)
+	return getProgramLinkError(*p)
+}
+
+func getProgramLinkError(p Program) error {
+
+	var linkSuccessful int32
+	gl.GetProgramiv(p.ID, gl.LINK_STATUS, &linkSuccessful)
+	if linkSuccessful == gl.TRUE {
+		return nil
+	}
+
+	//Get the log length and create a string big enough for it and fill it with NULL
+	var logLength int32
+	gl.GetProgramiv(p.ID, gl.INFO_LOG_LENGTH, &logLength)
+	infoLog := gl.Str(strings.Repeat("\x00", int(logLength)))
+
+	//Read the error log and return a go error
+	gl.GetProgramInfoLog(p.ID, logLength, nil, infoLog)
+	return fmt.Errorf("Program linking failed. Linking log: %s", gl.GoStr(infoLog))
+}
+
+func (p *Program) Use() {
+	gl.UseProgram(p.ID)
+}
+
+//Delete deletes all shaders and then deletes the program
+func (p *Program) Delete() {
+	for _, v := range p.Shaders {
+		v.Delete()
+	}
+
+	gl.DeleteProgram(p.ID)
+}