Implement the Container interface in lib/ui/

lib/ui/borders.go

@@ -30,6 +30,10 @@ func (bordered *Bordered) contentInvalidated(d Drawable) {
 	bordered.Invalidate()
 }
 
+func (bordered *Bordered) Children() []Drawable {
+	return []Drawable{bordered.content}
+}
+
 func (bordered *Bordered) Invalidate() {
 	if bordered.onInvalidate != nil {
 		bordered.onInvalidate(bordered)

lib/ui/grid.go

@@ -71,6 +71,14 @@ func (grid *Grid) Columns(spec []GridSpec) *Grid {
 	return grid
 }
 
+func (grid *Grid) Children() []Drawable {
+	children := make([]Drawable, len(grid.cells))
+	for i, cell := range grid.cells {
+		children[i] = cell.Content
+	}
+	return children
+}
+
 func (grid *Grid) Draw(ctx *Context) {
 	invalid := grid.invalid
 	if invalid {

lib/ui/interfaces.go

@@ -31,12 +31,7 @@ type DrawableInteractive interface {
 // A drawable which contains other drawables
 type Container interface {
 	Drawable
-	// A list of all drawables which are children of this one (do not recurse
+	// Return all of the drawables which are children of this one (do not
-	// into your grandchildren).
+	// recurse into your grandchildren).
 	Children() []Drawable
-	// Return the "focused" child, or none of no preference. Does not actually
-	// have to be Interactive. If there is a preferred child, input events will
-	// be directed to it. If there's no preference, events will be delivered to
-	// all children.
-	InteractiveChild() Drawable
 }

lib/ui/stack.go

@@ -15,6 +15,10 @@ func NewStack() *Stack {
 	return &Stack{}
 }
 
+func (stack *Stack) Children() []Drawable {
+	return stack.children
+}
+
 func (stack *Stack) OnInvalidate(onInvalidate func(d Drawable)) {
 	stack.onInvalidate = append(stack.onInvalidate, onInvalidate)
 }

lib/ui/tab.go

@@ -107,6 +107,14 @@ func (strip *TabStrip) OnInvalidate(onInvalidate func(d Drawable)) {
 	strip.onInvalidateStrip = onInvalidate
 }
 
+func (content *TabContent) Children() []Drawable {
+	children := make([]Drawable, len(content.Tabs))
+	for i, tab := range content.Tabs {
+		children[i] = tab.Content
+	}
+	return children
+}
+
 func (content *TabContent) Draw(ctx *Context) {
 	if content.Selected >= len(content.Tabs) {
 		width := ctx.Width()