make loading script a method of window

cmd/window.go

@@ -49,25 +49,35 @@ type script struct {
 	Times   []float64
 }
 
-func readScript(scriptPath string) (*script, error) {
+func (m *milkDropWindow) loadScript(scriptPath string) error {
 	if scriptPath == "" {
-		return nil, errors.New("no script given")
+		return errors.New("no script given")
 	}
 
 	f, err := os.Open(scriptPath)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	defer f.Close()
 
 	data, err := io.ReadAll(f)
 	if err != nil {
-		return nil, err
+		return err
 	}
 
 	var s script
 	err = json.Unmarshal(data, &s)
-	return &s, err
+	if err != nil {
+		return err
+	}
+
+	m.preset = ring.New(len(s.Presets))
+	for _, preset := range s.Presets {
+		m.preset.Value = preset
+		m.preset = m.preset.Next()
+	}
+
+	return nil
 }
 
 func (m *milkDropWindow) nextPreset() {
@@ -82,19 +92,12 @@ func (m *milkDropWindow) prevPreset() {
 
 func newMilkDropWindow(width, height int32, scriptPath string) (*milkDropWindow, error) {
 	var m milkDropWindow
-	var err error
 
-	s, err := readScript(scriptPath)
+	err := m.loadScript(scriptPath)
 	if err != nil {
 		return nil, err
 	}
 
-	m.preset = ring.New(len(s.Presets))
-	for _, preset := range s.Presets {
-		m.preset.Value = preset
-		m.preset = m.preset.Next()
-	}
-
 	m.window, err = sdl.CreateWindow("milkbucket", sdl.WINDOWPOS_UNDEFINED, sdl.WINDOWPOS_UNDEFINED, width, height, sdl.WINDOW_OPENGL|sdl.WINDOW_RESIZABLE)
 	if err != nil {
 		return &m, err