Changed Stack so that controls are added only at creation time.

main.go

@@ -10,8 +10,7 @@ func main() {
 	w.Closing = make(chan struct{})
 	b := NewButton("Click Me")
 	c := NewCheckbox("Check Me")
-	s := NewStack(Vertical)
-	s.Controls = []Control{b, c}
+	s := NewStack(Vertical, b, c)
 	err := w.Open(s)
 	if err != nil {
 		panic(err)

stack.go

@@ -15,27 +15,26 @@ const (
 
 // A Stack stacks controls horizontally or vertically within the Stack's parent, alotting each the same size.
 type Stack struct {
-	// The controls of the Stack. Once the Window containing the Stack has been created, this should not be modified.
-	Controls		[]Control
-
 	lock			sync.Mutex
 	created		bool
 	orientation	Orientation
+	controls		[]Control
 }
 
 // NewStack creates a new Stack with the specified orientation.
-func NewStack(o Orientation) *Stack {
+func NewStack(o Orientation, controls ...Control) *Stack {
 	if o != Horizontal && o != Vertical {
 		panic(fmt.Sprintf("invalid orientation %d given to NewStack()", o))
 	}
 	return &Stack{
 		orientation:	o,
+		controls:		controls,
 	}
 }
 
 // TODO adorn errors with which stage failed
 func (s *Stack) apply(window *sysData) error {
-	for _, c := range s.Controls {
+	for _, c := range s.controls {
 		err := c.apply(window)
 		if err != nil {
 			return err
@@ -48,20 +47,20 @@ func (s *Stack) apply(window *sysData) error {
 func (s *Stack) setRect(x int, y int, width int, height int) error {
 	var dx, dy int
 
-	if len(s.Controls) == 0 {		// do nothing if there's nothing to do
+	if len(s.controls) == 0 {		// do nothing if there's nothing to do
 		return nil
 	}
 	switch s.orientation {
 	case Horizontal:
-		dx = width / len(s.Controls)
+		dx = width / len(s.controls)
 		width = dx
 	case Vertical:
-		dy = height / len(s.Controls)
+		dy = height / len(s.controls)
 		height = dy
 	default:
 		panic(fmt.Sprintf("invalid orientation %d given to Stack.setRect()", s.orientation))
 	}
-	for _, c := range s.Controls {
+	for _, c := range s.controls {
 		err := c.setRect(x, y, width, height)
 		if err != nil {
 			return err