Refactor OpenGL-related Code

2 files changed, 39 insertions, 24 deletions

diff --git a/graphics.go b/graphics.go
index 6cb3400..91edcce 100644
--- a/graphics.go
+++ b/graphics.go
@@ -39,37 +39,54 @@ const (
     ` + "\x00"
 )
 
-// initOpenGL initializes OpenGL and returns an intiialized program
-func initOpenGL() uint32 {
-	log.Println("OpenGL init")
+type Graphics struct {
+	version string
+	vao uint32
+	vertexShader uint32
+	fragmentShader uint32
+	program uint32
+}
+
+func newGraphics() Graphics {
 
-	if err := gl.Init(); err != nil {
-		panic(err)
+	var graphics Graphics = Graphics{}
+
+	// init OpenGL and save/log version
+	log.Println("OpenGL init")
+	err := gl.Init()
+	if err != nil {
+		log.Fatal(err)
 	}
-	version := gl.GoStr(gl.GetString(gl.VERSION))
-	log.Println("OpenGL version", version)
+	graphics.version = gl.GoStr(gl.GetString(gl.VERSION))
+	log.Println("OpenGL version", graphics.version)
 
-	vertexShader, err := compileShader(VERTEX_SHADER, gl.VERTEX_SHADER)
+	// compile shaders
+	graphics.vertexShader, err = compileShader(VERTEX_SHADER, gl.VERTEX_SHADER)
 	if err != nil {
-		panic(err)
+		log.Fatal(err)
 	}
-	fragmentShader, err := compileShader(FRAGMENT_SHADER, gl.FRAGMENT_SHADER)
+	graphics.fragmentShader, err = compileShader(FRAGMENT_SHADER, gl.FRAGMENT_SHADER)
 	if err != nil {
-		panic(err)
+		log.Fatal(err)
 	}
 
-	prog := gl.CreateProgram()
-	gl.AttachShader(prog, vertexShader)
-	gl.AttachShader(prog, fragmentShader)
-	gl.LinkProgram(prog)
-	return prog
+	// create GL program
+	graphics.program = gl.CreateProgram()
+	gl.AttachShader(graphics.program, graphics.vertexShader)
+	gl.AttachShader(graphics.program, graphics.fragmentShader)
+	gl.LinkProgram(graphics.program)
+
+	// create VAO
+	graphics.vao = makeVao(triangle)
+
+	return graphics
 }
 
-func draw(vao uint32, program uint32) {
+func (graphics Graphics) draw() {
 	gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
-	gl.UseProgram(program)
+	gl.UseProgram(graphics.program)
 
-	gl.BindVertexArray(vao)
+	gl.BindVertexArray(graphics.vao)
 	gl.DrawArrays(gl.TRIANGLES, 0, int32(len(triangle)/3))
 }
 
diff --git a/main.go b/main.go
index e2d6e43..8f2afcc 100644
--- a/main.go
+++ b/main.go
@@ -30,15 +30,13 @@ func main() {
 	var app App = newApp()
 	defer app.terminate()  // GLFW needs to be terminated!
 
-	// init OpenGL
-	program := initOpenGL()
-
-	vao := makeVao(triangle)
+	// initialize graphics
+	var graphics Graphics = newGraphics()
 
 	// main loop
 	for !app.window.ShouldClose() {
+		graphics.draw()
 		app.handle()
-		draw(vao, program)
 	}
 }