https://invisible-island.net/ncurses/man/
curs_kernel(3x) Library calls curs_kernel(3x)
def_prog_mode, def_shell_mode, reset_prog_mode, reset_shell_mode,
resetty, savetty, getsyx, setsyx, curs_set, mvcur, napms, ripoffline -
low-level curses routines
#include <curses.h>
int def_prog_mode(void);
int def_shell_mode(void);
int reset_prog_mode(void);
int reset_shell_mode(void);
int resetty(void);
int savetty(void);
void getsyx(int y, int x);
void setsyx(int y, int x);
int curs_set(int visibility);
int mvcur(int oldrow, int oldcol, int newrow, int newcol);
int napms(int ms);
int ripoffline(int line, int (*init)(WINDOW *, int));
The following routines give low-level access to various curses
capabilities. These routines typically are used inside library
routines.
The def_prog_mode and def_shell_mode routines save the current terminal
modes as the "program" (in curses) or "shell" (not in curses) state for
use by the reset_prog_mode and reset_shell_mode routines. This is done
automatically by initscr. There is one such save area for each screen
context allocated by newterm.
The reset_prog_mode and reset_shell_mode routines restore the terminal
to "program" (in curses) or "shell" (out of curses) state. These are
done automatically by endwin(3x) and, after an endwin, by doupdate, so
they normally are not called.
The resetty and savetty routines save and restore the state of the
terminal modes. savetty saves the current state in a buffer and
resetty restores the state to what it was at the last call to savetty.
getsyx stores the coordinates of virtual screen (newscr) cursor in y
and x. If newscr's leaveok(3x) output option is TRUE, getsyx stores -1
in both y and x. If lines have been removed from the top of the screen
using ripoffline, y includes these lines; therefore, y and x populated
by getsyx should be used only as arguments for setsyx.
Few applications use this feature; most call getyx(3x) instead.
setsyx sets the virtual screen (newscr) cursor location to (y, x).
setsyx(-1, -1) is equivalent to leaveok(newscr, TRUE).
getsyx and setsyx are designed to be used by a function that
manipulates curses windows but seeks to avoid changing the cursor
position. Such a function would first call getsyx, modify its windows'
content, call wnoutrefresh(3x) on them, call setsyx, then call
doupdate(3x).
Few applications use this feature; most call wmove(3x) instead.
curs_set adjusts the cursor visibility to "invisible", "visible", "very
visible", as its argument is 0, 1, or 2, respectively. It returns the
previous visibility if the requested one is supported, and ERR
otherwise.
mvcur provides low-level cursor motion. It takes effect immediately,
rather than at the next refresh. Unlike the other low-level output
functions, which either write to the standard output stream or are
passed a function pointer to perform output, mvcur uses a file
descriptor derived from the output stream parameter of newterm(3x).
One application of mvcur accompanies the temporary use of another
program to write to the terminal screen. For example, first call
refresh(3x) to ensure that the screen and the library's model of it are
up to date; then call reset_shell_mode; write to the screen with the
external application; call reset_prog_mode; and finally call mvcur(...,
..., -1, -1) to move the terminal cursor to where curses thinks it is,
since the library has no knowledge of how the external application
moved it.
napms sleeps for ms milliseconds. If ms exceeds 30,000 (thirty
seconds), ncurses caps it at that value.
ripoffline provides access to the same facility that slk_init(3x) uses
to reduce the size of the screen. The application must call ripoffline
before initscr(3x) or newterm(3x) so that the latter functions prepare
a stdscr of the correct size.
o If line is positive, ripoffline removes a line from the top of what
will become stdscr.
o If line is negative, ripoffline removes a line from the bottom of
what will become stdscr.
When initscr initializes curses, it calls the init function supplied to
ripoffline by the application with two arguments:
o a pointer to the one-line WINDOW that it allocates, and
o an integer with the number of columns in the window.
Inside this init function, the values of the integer variables LINES
and COLS (see curs_variables(3x)) are not guaranteed to be reliable; it
must not call wrefresh(3x) or doupdate(3x). A wnoutrefresh(3x) call is
permissible.
ripoffline can be called up to five times before initscr or newterm.
Except for curs_set, these functions return OK on success and ERR on
failure.
curs_set returns the previous cursor visibility, and returns ERR if the
terminal type does not support the requested visibility.
napms always succeeds.
mvcur fails if the position (newrow, newcol) is outside the screen
boundaries.
In ncurses,
o def_prog_mode, def_shell_mode, reset_prog_mode, and
reset_shell_mode return ERR if the terminal was not initialized, or
if the operating system's function for obtaining terminal settings
fails.
o ripoffline returns ERR if the accumulated quantity of ripped-off
lines would exceed the maximum (5).
getsyx is a macro; use of the & operator before its arguments is
unnecessary.
The endwin function of both ncurses and SVr4 curses calls curs_set if
the latter has previously been called to set the cursor visibility to a
value other than normal; that is, either invisible or very visible.
There is no way for ncurses to determine the initial cursor visibility
to restore it.
ncurses imposes a limit of 30 seconds on a delay requested of napms.
While the init function called by ripoffline is specified to return an
int, ncurses pays no attention to its return value.
If ripoffline cannot allocate memory for the required WINDOW structure
backing the ripped-off line, it stores a null pointer to the WINDOW
pointer argument supplied by the init function the application
specifies. The application must check this argument for validity after
calling initscr and prior to performing curses operations on that
window.
In ncurses, mvcur accepts -1 for either or both old coordinates. This
value tells ncurses that the old location is unknown, and that it must
use only absolute motion, as with the cursor_address (cup) capability,
rather than the least costly combination of absolute and relative
motion.
Applications employing ncurses extensions should condition their use on
the visibility of the NCURSES_VERSION preprocessor macro.
The virtual screen functions setsyx and getsyx are not described in
X/Open Curses Issue 4. SVr4 documents each of them as returning an
int. This is misleading, as they are macros with no documented
semantics for returning values.
All other functions are as described in X/Open Curses. It specifies no
error conditions for them, except as described for curs_set in section
"RETURN VALUE" above.
The System V Interface Definition, Version 4 (1995), specified all of
these functions except curs_set as returning OK.
Older SVr4 man pages warn that the return value of curs_set "is
currently incorrect". This implementation gets it right, but counting
on its correctness anywhere else may be unwise.
X/Open Curses specifies ripoffline as returning OK with no possibility
of failure ("[c]alls to ripoffline above this limit [five lines] have
no effect but report success").
X/Open Curses notes:
After use of mvcur(), the model Curses maintains of the state of
the terminal might not match the actual state of the terminal.
An application should touch and refresh the window before
resuming conventional use of Curses.
Both ncurses and SVr4 curses implement mvcur using the SCREEN object
allocated in either initscr(3x) or newterm(3x). X/Open Curses states
that the old location must be given for mvcur to accommodate terminals
that lack absolute cursor positioning.
If interrupted by a signal, ncurses restarts napms. That, and the
limitation to 30 seconds, differ from other implementations.
curses(3x), curs_initscr(3x), curs_outopts(3x), curs_refresh(3x),
curs_scr_dump(3x), curs_slk(3x), curs_variables(3x)
ncurses 6.5 2025-08-16 curs_kernel(3x)