Changed 'Tabbable/Focusable' logic to use Active

wdgt_stacked_layout.go

@@ -155,7 +155,7 @@ func (w *ScrollingWidgetList) Draw(screen tcell.Screen) {
 
 func (w *ScrollingWidgetList) SetStyle(s tcell.Style) { w.style = s }
 func (w *ScrollingWidgetList) Active() bool           { return w.active }
-func (w *ScrollingWidgetList) SetActive(a bool) {
+func (w *ScrollingWidgetList) SetActive(a bool) bool {
 	w.active = a
 	if w.active {
 		act := w.findActiveOrFirst()
@@ -163,6 +163,7 @@ func (w *ScrollingWidgetList) SetActive(a bool) {
 			act.SetActive(true)
 		}
 	}
+	return w.active
 }
 func (w *ScrollingWidgetList) Visible() bool       { return w.visible }
 func (w *ScrollingWidgetList) SetVisible(a bool)   { w.visible = a }