the #GtkClipboard
a #GtkSelectionData argument in which the requested data should be stored.
the info field corresponding to the requested target from the #GtkTargetEntry array passed to gtk_clipboard_set_with_data() or gtk_clipboard_set_with_owner().
the user_data argument passed to gtk_clipboard_set_with_data(), or the owner argument passed to gtk_clipboard_set_with_owner()
A function that will be called to provide the contents of the selection. If multiple types of data were advertised, the requested type can be determined from the
infoparameter or by checking the target field ofselection_data. If the data could successfully be converted into then it should be stored into theselection_dataobject by calling gtk_selection_data_set() (or related functions such as gtk_selection_data_set_text()). If no data is set, the requestor will be informed that the attempt to get the data failed.