kernel(3NCURSES) Library calls kernel(3NCURSES)
NAME
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
SYNOPSIS
#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));
DESCRIPTION
The following routines give low-level access to various curses capabili-
ties. These routines typically are used inside library routines.
def_prog_mode, def_shell_mode
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.
reset_prog_mode, reset_shell_mode
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(3NCURSES) and, after an endwin, by doup-
date, so they normally are not called.
resetty, savetty
The resetty and savetty routines save and restore the state of the ter-
minal 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
getsyx stores the coordinates of virtual screen (newscr) cursor in y and
x. If newscr's leaveok(3NCURSES) 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 pop-
ulated by getsyx should be used only as arguments for setsyx.
Few applications use this feature; most call getyx(3NCURSES) instead.
setsyx
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(3NCURSES) on them, call setsyx, then call
doupdate(3NCURSES).
Few applications use this feature; most call wmove(3NCURSES) instead.
curs_set
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 other-
wise.
mvcur
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 descrip-
tor derived from the output stream parameter of newterm(3NCURSES).
One application of mvcur accompanies the temporary use of another pro-
gram to write to the terminal screen. For example, first call
refresh(3NCURSES) to ensure that the screen and the library's model of
it is 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 ap-
plication moved it.
napms
napms sleeps for ms milliseconds. If ms exceeds 30,000 (thirty sec-
onds), it is capped at that value.
ripoffline
ripoffline provides access to the same facility that slk_init(3NCURSES)
uses to reduce the size of the screen. ripoffline must be called before
initscr or newterm is called, to prepare these initial actions:
• If line is positive, a line is removed from the top of stdscr.
• if line is negative, a line is removed from the bottom.
When the resulting initialization is done inside initscr, the routine
init (supplied by the user) is called with two arguments:
• a window pointer to the one-line window that has been allocated and
• an integer with the number of columns in the window.
Inside this initialization routine, the integer variables LINES and COLS
(defined in <curses.h>) are not guaranteed to be accurate and wrefresh
or doupdate must not be called. It is allowable to call wnoutrefresh
during the initialization routine.
ripoffline can be called up to five times before calling initscr or
newterm.
RETURN VALUE
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,
• 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.
• ripoffline returns ERR if the accumulated quantity of ripped-off
lines would exceed the maximum (5).
NOTES
getsyx is a macro; use of the & operator before its arguments is unnec-
essary.
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.
EXTENSIONS
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 mo-
tion.
PORTABILITY
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 cur-
rently 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 resum-
ing conventional use of Curses.
Both ncurses and SVr4 curses implement mvcur using the SCREEN object al-
located in either initscr(3NCURSES) or newterm(3NCURSES). X/Open Curses
states that the old location must be given for mvcur to accommodate ter-
minals that lack absolute cursor positioning.
If interrupted by a signal, ncurses restarts napms. That, and the limi-
tation to 30 seconds, differ from other implementations.
SEE ALSO
ncurses(3NCURSES), initscr(3NCURSES), outopts(3NCURSES),
refresh(3NCURSES), scr_dump(3NCURSES), slk(3NCURSES),
curses_variables(3NCURSES)
ncurses 6.5 2025-02-15 kernel(3NCURSES)
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