GtkExpander A container which can hide its child A #GtkExpander allows the user to hide or show its child by clicking on an expander triangle similar to the triangles used in a #GtkTreeView. @expander: the object which received the signal. @label: @Returns: @label: @Returns: @expander: @expanded: @expander: @Returns: @expander: @spacing: @expander: @Returns: @expander: @label: @expander: @Returns: @expander: @use_underline: @expander: @Returns: @expander: @use_markup: @expander: @Returns: @expander: @label_widget: @expander: @Returns: