+On the other platforms, there is no PRIMARY selection and so all clipboard
+operations will fail. This allows to implement the standard X11 handling of the
+clipboard which consists in copying data to the CLIPBOARD selection only when
+the user explicitly requests it (i.e. by selection \texttt{"Copy"} menu
+command) but putting the currently selected text into the PRIMARY selection
+automatically, without overwriting the normal clipboard contents with the
+currently selected text on the other platforms.