GladePlaceholder — A GtkWidget to fill empty places.
GObject ╰── GInitiallyUnowned ╰── GtkWidget ╰── GladePlaceholder
GladePlaceholder implements AtkImplementorIface, GtkBuildable, GtkScrollable and _GladeDrag.
Generally in Glade, container widgets are implemented with GladePlaceholder
children to allow users to 'click' and add thier widgets to a container.
It is the responsability of the plugin writer to create placeholders for
container widgets where appropriate; usually in GladePostCreateFunc
when the GladeCreateReason is
GtkWidget * glade_placeholder_new (
a new GladePlaceholder cast as a GtkWidget
GladeWidget * glade_placeholder_get_parent (