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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 <ncursesw/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 capabilities. 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 doupdate, so they normally are not called.

resetty, savetty

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

The getsyx routine returns the current coordinates of the virtual screen cursor in y and x. If leaveok is currently TRUE, then -1,-1 is returned. If lines have been removed from the top of the screen, using ripoffline, y and x include these lines; therefore, y and x should be used only as arguments for setsyx.

Few applications will use this feature, most use getyx instead.

setsyx

The setsyx routine sets the virtual screen cursor to y, x. If y and x are both -1, then leaveok is set. The two routines getsyx and setsyx are designed to be used by a library routine, which manipulates curses windows but does not want to change the current position of the program's cursor. The library routine would call getsyx at the beginning, do its manipulation of its own windows, do a wnoutrefresh on its windows, call setsyx, and then call doupdate.

Few applications will use this feature, most use wmove instead.

curs_set

The curs_set routine sets the cursor state to invisible, normal, or very visible for visibility equal to 0, 1, or 2 respectively. If the terminal supports the visibility requested, the previous cursor state is returned; otherwise, ERR is returned.

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 descriptor derived from the output stream parameter of newterm(3NCURSES).

One application of mvcur accompanies the temporary use of another program 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 to set the cursor's location to where curses thinks it is, since the library has no knowledge of how the external application moved it.

napms

napms sleeps for ms milliseconds. If ms exceeds 30,000 (thirty seconds), 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 routines always return OK.

curs_set returns the previous cursor state, or ERR if the requested visibility is not supported.

X/Open defines no error conditions. In this implementation

return ERR if the terminal was not initialized, or if the I/O call to obtain the terminal settings fails.
ripoffline
returns ERR if the maximum number of ripped-off lines exceeds the maximum (5).

NOTES

Note that getsyx is a macro, so & is not necessary before the variables y and x.

Older SVr4 man pages warn that the return value of curs_set “is currently incorrect”. This implementation gets it right, but it may be unwise to count on the correctness of the return value anywhere else.

Both ncurses and SVr4 will call curs_set in endwin if curs_set has been called to make the cursor other than normal, i.e., either invisible or very visible. There is no way for ncurses to determine the initial cursor state to restore that.

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 motion.

PORTABILITY

The virtual screen functions setsyx and getsyx are not described in X/Open Curses, Issue 4. All other functions are as described in X/Open Curses.

The SVr4 documentation describes setsyx and getsyx as having return type int. This is misleading, as they are macros with no documented semantics for the return value.

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 data allocated in either initscr(3NCURSES) or newterm(3NCURSES). X/Open Curses states that the old location must be given for mvcur to accommodate terminals that lack absolute cursor positioning.

If interrupted, ncurses restarts napms. That, and the limitation to 30 seconds, are different from other implementations.

SEE ALSO

ncurses(3NCURSES), initscr(3NCURSES), outopts(3NCURSES), refresh(3NCURSES), scr_dump(3NCURSES), slk(3NCURSES), curses_variables(3NCURSES)

2024-05-25 ncurses 6.5