WidgetLayout is an option to Widget, WidgetReference, and WidgetGroup that contains suboptions controlling layout.
Widget
(GUIKit Package Symbol) Widget[class : class | path | URL[path], {content}] defines a new widget instance.
WidgetReference[id] looks up an existing widget instance using identifier id and return the underlying object.
WidgetSpace[] is a widget layout placeholder used when spacing is needed between widgets.
WidgetToSymbolicGUIKitXML[expr] converts a user interface expression to a GUIKitXML SymbolicXML expression.
$GUIPath lists the directories searched in attempting to find interface files.
Widget["Button"] represents a button.
Widget["CheckBox"] represents a checkbox.
Widget["ColorChooser"] provides a panel for making a color selection from various color model interfaces.
Widget["ComboBox"] represents a combo box.