Added Stacks of controls.

main.go

@@ -9,14 +9,10 @@ func main() {
 	w := NewWindow("Main Window", 320, 240)
 	w.Closing = make(chan struct{})
 	b := NewButton("Click Me")
-	err := w.Open(b)
-	if err != nil {
-		panic(err)
-	}
-
-	w2 := NewWindow("Checkbox Window", 200, 100)
 	c := NewCheckbox("Check Me")
-	err = w2.Open(c)
+	s := NewStack(Vertical)
+	s.Controls = []Control{b, c}
+	err := w.Open(s)
 	if err != nil {
 		panic(err)
 	}

stack.go

@@ -0,0 +1,73 @@
+// 13 february 2014
+package main
+
+import (
+	"fmt"
+	"sync"
+)
+
+// Orientation defines the orientation of controls in a Stack.
+type Orientation int
+const (
+	Horizontal Orientation = iota
+	Vertical
+)
+
+// 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
+}
+
+// NewStack creates a new Stack with the specified orientation.
+func NewStack(o Orientation) *Stack {
+	if o != Horizontal && o != Vertical {
+		panic(fmt.Sprintf("invalid orientation %d given to NewStack()", o))
+	}
+	return &Stack{
+		orientation:	o,
+	}
+}
+
+// TODO adorn errors with which stage failed
+func (s *Stack) apply(window *sysData) error {
+	for _, c := range s.Controls {
+		err := c.apply(window)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// TODO adorn errors with which stage failed
+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
+		return nil
+	}
+	switch s.orientation {
+	case Horizontal:
+		dx = width / len(s.Controls)
+		width = dx
+	case Vertical:
+		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 {
+		err := c.setRect(x, y, width, height)
+		if err != nil {
+			return err
+		}
+		x += dx
+		y += dy
+	}
+	return nil
+}

todo.md

@@ -2,6 +2,7 @@ so I don't forget:
 - Window.SizeToFit() or WIndow.OptimalSize() (use: `Window.SetSize(Window.OptimalSize())`) for sizing a window to the control's interest
 - Control.Show()/Control.Hide()
 - Control.SetText()
+- Groupbox
 
 super ultra important things:
 - the windows build appears to be unstable:
@@ -16,3 +17,7 @@ far off:
 - localization
 - strip unused constants from the Windows files
 - combine more Windows files; rename some?
+- normalize error handling to adorn errors with function call information
+
+maybe:
+- rename Stack to Box?