Add ItemSelectedCallback to MenuBar & make Menus field private

main.go

@@ -79,10 +79,16 @@ func main() {
 
 	var fileSelector *ui.FileSelectorDialog // if nil, we don't draw it
 
-	bar := ui.NewMenuBar(&theme)
-
 	barFocused := false
 
+	bar := ui.NewMenuBar(&theme)
+	bar.ItemSelectedCallback = func() {
+		// When something is selected in the MenuBar,
+		// we change focus back to the tab container.
+		changeFocus(tabContainer)
+		barFocused = false
+	}
+
 	fileMenu := ui.NewMenu("_File", &theme)
 
 	fileMenu.AddItems([]ui.Item{&ui.ItemEntry{Name: "_New File", Callback: func() {