selection-coding-system

selection-coding-system is a variable defined in `select.el'.
Its value is

nil

Documentation:
Coding system for communicating with other programs.

For MS-Windows and MS-DOS:
When sending or receiving text via selection and clipboard, the text
is encoded or decoded by this coding system. The default value is
the current system default encoding on 9x/Me, `utf-16le-dos'
(Unicode) on NT/W2K/XP, and `iso-latin-1-dos' on MS-DOS.

For X Windows:
When sending text via selection and clipboard, if the target
data-type matches with the type of this coding system, it is used
for encoding the text. Otherwise (including the case that this
variable is nil), a proper coding system is used as below:

data-type coding system
--------- -------------
UTF8_STRING utf-8
COMPOUND_TEXT compound-text-with-extensions
STRING iso-latin-1
C_STRING no-conversion

When receiving text, if this coding system is non-nil, it is used
for decoding regardless of the data-type. If this is nil, a
proper coding system is used according to the data-type as above.

See also the documentation of the variable `x-select-request-type' how
to control which data-type to request for receiving text.

The default value is nil.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 23.1 of Emacs.