x-lost-selection-hooks

x-lost-selection-hooks is a variable defined in `subr.el'.
Its value is

nil

• This variable is an alias for `x-lost-selection-functions'.
• This variable is obsolete since 22.1;
  use `x-lost-selection-functions' instead.
• This variable may be risky if used as a file-local variable.

Documentation:
A list of functions to be called when Emacs loses an X selection.
(This happens when some other X client makes its own selection
or when a Lisp program explicitly clears the selection.)
The functions are called with one argument, the selection type
(a symbol, typically `PRIMARY', `SECONDARY', or `CLIPBOARD').