populate-popup
Emitted when a context menu for the label is popped up.
A context menu will normally be popped up when a user right clicks on a selectable label. When this signal is emitted, the context menu is passed to the callback.
This signal cannot be emitted unless the label has been made selectable by passing true to set_selectable() , because text that is not selectable will not have a context menu.
Callback function