Added Box. Phew! Now to port over the libui test program...

box.go

@@ -0,0 +1,121 @@
+// 12 december 2015
+
+package ui
+
+import (
+	"unsafe"
+)
+
+// #include "ui.h"
+import "C"
+
+// Box is a Control that holds a group of Controls horizontally
+// or vertically. If horizontally, then all controls have the same
+// height. If vertically, then all controls have the same width.
+// By default, each control has its preferred width (horizontal)
+// or height (vertical); if a control is marked "stretchy", it will
+// take whatever space is left over. If multiple controls are marked
+// stretchy, they will be given equal shares of the leftover space.
+// There can also be space between each control ("padding").
+type Box struct {
+	c	*C.uiControl
+	b	*C.uiBox
+
+	children	[]Control
+}
+
+// NewHorizontalBox creates a new horizontal Box.
+func NewHorizontalBox() *Box {
+	b := new(Box)
+
+	b.b = C.uiNewHorizontalBox()
+	b.c = (*C.uiControl)(unsafe.Pointer(b.b))
+
+	return b
+}
+
+// NewVerticalBox creates a new vertical Box.
+func NewVerticalBox() *Box {
+	b := new(Box)
+
+	b.b = C.uiNewVerticalBox()
+	b.c = (*C.uiControl)(unsafe.Pointer(b.b))
+
+	return b
+}
+
+// Destroy destroys the Box. If the Box has children,
+// Destroy calls Destroy on those Controls as well.
+func (b *Box) Destroy() {
+	for len(b.children) != 0 {
+		c := b.children[0]
+		b.Delete(0)
+		c.Destroy()
+	}
+	C.uiControlDestroy(b.c)
+}
+
+// LibuiControl returns the libui uiControl pointer that backs
+// the Box. This is only used by package ui itself and should
+// not be called by programs.
+func (b *Box) LibuiControl() uintptr {
+	return uintptr(unsafe.Pointer(b.c))
+}
+
+// Handle returns the OS-level handle associated with this Box.
+// On Windows this is an HWND of a libui-internal class.
+// On GTK+ this is a pointer to a GtkBox.
+// On OS X this is a pointer to a NSView.
+func (b *Box) Handle() uintptr {
+	return uintptr(C.uiControlHandle(b.c))
+}
+
+// Show shows the Box.
+func (b *Box) Show() {
+	C.uiControlShow(b.c)
+}
+
+// Hide hides the Box.
+func (b *Box) Hide() {
+	C.uiControlHide(b.c)
+}
+
+// Enable enables the Box.
+func (b *Box) Enable() {
+	C.uiControlEnable(b.c)
+}
+
+// Disable disables the Box.
+func (b *Box) Disable() {
+	C.uiControlDisable(b.c)
+}
+
+// Append adds the given control to the end of the Box.
+func (b *Box) Append(child Control, stretchy bool) {
+	c := (*C.uiControl)(nil)
+	if child != nil {
+		c = touiControl(child.LibuiControl())
+	}
+	C.uiBoxAppend(b.b, c, frombool(stretchy))
+	b.children = append(b.children, child)
+}
+
+// Delete deletes the nth control of the Box.
+func (b *Box) Delete(n int) {
+	b.children = append(b.children[:n], b.children[n + 1:]...)
+	// TODO why is this uintmax_t instead of intmax_t
+	C.uiBoxDelete(b.b, C.uintmax_t(n))
+}
+
+// Padded returns whether there is space between each control
+// of the Box.
+func (b *Box) Padded() bool {
+	return tobool(C.uiBoxPadded(b.b))
+}
+
+// SetPadded controls whether there is space between each control
+// of the Box. The size of the padding is determined by the OS and
+// its best practices.
+func (b *Box) SetPadded(padded bool) {
+	C.uiBoxSetPadded(b.b, frombool(padded))
+}

tab.go

@@ -11,7 +11,7 @@ import "C"
 
 // Tab is a Control that holds tabbed pages of Controls. Each tab
 // has a label. The user can click on the tabs themselves to switch
-// pages.
+// pages. Individual pages can also have margins.
 type Tab struct {
 	c	*C.uiControl
 	t	*C.uiTab

zz_test.go

@@ -11,12 +11,16 @@ func TestIt(t *testing.T) {
 			Quit()
 			return true
 		})
-		t := NewTab()
-		w.SetChild(t)
+		b := NewVerticalBox()
+		w.SetChild(b)
 		w.SetMargined(true)
-		t.Append("First Page", NewButton("Click Me"))
-		t.Append("Second Page", NewButton("Click Me Too"))
-		t.SetMargined(0, true)
+		button := NewButton("Click Me")
+		button.OnClicked(func(*Button) {
+			b.SetPadded(!b.Padded())
+		})
+		b.Append(button, true)
+		b.Append(NewButton("Button 2"), false)
+		b.Append(NewButton("Button 3"), true)
 		w.Show()
 	})
 	if err != nil {