gui-get-selection-alist

gui-get-selection-alist is a variable defined in `select.el'.
Its value is

((x . x-get-selection-internal) (nil . ignore))

Documentation:
Return selected text.
Called with 2 arguments: (SELECTION-SYMBOL TARGET-TYPE)
SELECTION-SYMBOL is typically `PRIMARY', `SECONDARY', or `CLIPBOARD'.
(Those are literal upper-case symbol names, since that's what X expects.)
TARGET-TYPE is the type of data desired, typically `STRING'.