x-sent-selection-hooks

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

nil

• This variable is an alias for `x-sent-selection-functions'.
• This variable is obsolete since 22.1;
  use `x-sent-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 answers a selection request.
The functions are called with three arguments:
- the selection name (typically `PRIMARY', `SECONDARY', or `CLIPBOARD');
- the selection-type which Emacs was asked to convert the
selection into before sending (for example, `STRING' or `LENGTH');
- a flag indicating success or failure for responding to the request.
We might have failed (and declined the request) for any number of reasons,
including being asked for a selection that we no longer own, or being asked
to convert into a type that we don't know about or that is inappropriate.
This hook doesn't let you change the behavior of Emacs's selection replies,
it merely informs you that they have happened.