add Disable() and Enable()

action.go

@@ -103,6 +103,14 @@ func show(n *tree.Node, b bool) {
 	}
 }
 
+func enableWidget(n *tree.Node) {
+	enable(n, true)
+}
+
+func disableWidget(n *tree.Node) {
+	enable(n, false)
+}
+
 func enable(n *tree.Node, b bool) {
 	if !ready(n) {
 		return

treeInit.go

@@ -60,6 +60,10 @@ func initTree() *tree.TreeInfo {
 	t.SetLabel = setLabel
 	t.SetText = setText
 	t.AddText = addText
+
+	t.Enable = enableWidget
+	t.Disable = disableWidget
+
 	t.SetChecked = setChecked
 	t.ToolkitClose = toolkitClose
 	t.ShowTable = showTable