https://invisible-island.net/ncurses/man/
legacy_coding(3x) Library calls legacy_coding(3x)
use_legacy_coding - override curses locale encoding checks
#include <curses.h>
int use_legacy_coding(int level);
use_legacy_coding is an extension to the curses library. It allows the
caller to change the result of unctrl(3x), suppressing isprint(3)-based
checks within the library that would normally cause nonprinting
characters to be rendered in visible form. The alteration affects only
eight-bit characters.
The level parameter controls the result.
0 The library functions normally, rendering nonprinting
characters as described in unctrl(3x),
1 the library ignores isprint for codes in the range 160-255.
2 the library ignores isprint for codes in the range 128-255.
It also modifies the output of unctrl(3x), showing codes in
the range 128-159 as is.
If the screen has not been initialized, or the level parameter is out
of range, use_legacy_coding returns ERR. Otherwise, it returns the
previous level: 0, 1, or 2.
use_legacy_coding is specific to ncurses. It was not supported on
Version 7, BSD or System V implementations. Applications employing
ncurses extensions should condition their use on the visibility of the
NCURSES_VERSION preprocessor macro.
Thomas Dickey (to support lynx(1)'s font-switching feature).
unctrl(3x)
ncurses 6.4 2024-04-20 legacy_coding(3x)