clearok, idlok, idcok, immedok, leaveok, setscrreg, wsetscrreg, scrol-
lok, nl, nonl - curses output options
int clearok(WINDOW *win, bool bf);
int idlok(WINDOW *win, bool bf);
void idcok(WINDOW *win, bool bf);
void immedok(WINDOW *win, bool bf);
int leaveok(WINDOW *win, bool bf);
int setscrreg(int top, int bot);
int wsetscrreg(WINDOW *win, int top, int bot);
int scrollok(WINDOW *win, bool bf);
These routines set options that change the style of output within
curses. All options are initially FALSE, unless otherwise stated. It
is not necessary to turn these options off before calling endwin.
If clearok is called with TRUE as argument, the next call to wrefresh
with this window will clear the screen completely and redraw the entire
screen from scratch. This is useful when the contents of the screen
are uncertain, or in some cases for a more pleasing visual effect. If
the win argument to clearok is the global variable curscr, the next
call to wrefresh with any window causes the screen to be cleared and
repainted from scratch.
If idlok is called with TRUE as second argument, curses considers using
the hardware insert/delete line feature of terminals so equipped.
Calling idlok with FALSE as second argument disables use of line inser-
tion and deletion. This option should be enabled only if the applica-
tion needs insert/delete line, for example, for a screen editor. It is
disabled by default because insert/delete line tends to be visually
annoying when used in applications where it isn't really needed. If
insert/delete line cannot be used, curses redraws the changed portions
of all lines.
If idcok is called with FALSE as second argument, curses no longer con-
siders using the hardware insert/delete character feature of terminals
so equipped. Use of character insert/delete is enabled by default.
Calling idcok with TRUE as second argument re-enables use of character
insertion and deletion.
If immedok is called with TRUE as argument, any change in the window
image, such as the ones caused by waddch, wclrtobot, wscrl, etc., auto-
matically cause a call to wrefresh. However, it may degrade perfor-
mance considerably, due to repeated calls to wrefresh. It is disabled
Normally, the hardware cursor is left at the location of the window
cursor being refreshed. The leaveok option allows the cursor to be
left wherever the update happens to leave it. It is useful for appli-
cations where the cursor is not used, since it reduces the need for
The setscrreg and wsetscrreg routines allow the application programmer
to set a software scrolling region in a window. top and bot are the
line numbers of the top and bottom margin of the scrolling region.
(Line 0 is the top line of the window.) If this option and scrollok
are enabled, an attempt to move off the bottom margin line causes all
lines in the scrolling region to scroll one line in the direction of
the first line. Only the text of the window is scrolled. (Note that
this has nothing to do with the use of a physical scrolling region
capability in the terminal, like that in the VT100. If idlok is
enabled and the terminal has either a scrolling region or insert/delete
line capability, they will probably be used by the output routines.)
The scrollok option controls what happens when the cursor of a window
is moved off the edge of the window or scrolling region, either as a
result of a newline action on the bottom line, or typing the last char-
acter of the last line. If disabled, (bf is FALSE), the cursor is left
on the bottom line. If enabled, (bf is TRUE), the window is scrolled
up one line (Note that to get the physical scrolling effect on the ter-
minal, it is also necessary to call idlok).
The nl and nonl routines control whether the underlying display device
translates the return key into newline on input, and whether it trans-
lates newline into return and line-feed on output (in either case, the
call addch('\n') does the equivalent of return and line feed on the
virtual screen). Initially, these translations do occur. If you dis-
able them using nonl, curses will be able to make better use of the
line-feed capability, resulting in faster cursor motion. Also, curses
will then be able to detect the return key.
The functions setscrreg and wsetscrreg return OK upon success and ERR
upon failure. All other routines that return an integer always return
These functions are described in the XSI Curses standard, Issue 4.
The XSI Curses standard is ambiguous on the question of whether raw()
should disable the CRLF translations controlled by nl() and nonl().
BSD curses did turn off these translations; AT&T curses (at least as
late as SVr1) did not. We choose to do so, on the theory that a pro-
grammer requesting raw input wants a clean (ideally 8-bit clean) con-
nection that the operating system does not mess with.
Some historic curses implementations had, as an undocumented feature,
the ability to do the equivalent of clearok(..., 1) by saying touch-
win(stdscr) or clear(stdscr). This will not work under ncurses.
Earlier System V curses implementations specified that with scrollok
enabled, any window modification triggering a scroll also forced a
physical refresh. XSI Curses does not require this, and ncurses avoids
doing it to perform better vertical-motion optimization at wrefresh
The XSI Curses standard does not mention that the cursor should be made
invisible as a side-effect of leaveok. SVr4 curses documentation does
this, but the code does not. Use curs_set to make the cursor invisi-
Note that clearok, leaveok, scrollok, idcok, nl, nonl and setscrreg may
The immedok routine is useful for windows that are used as terminal
curses(3X), curs_addch(3X), curs_clear(3X), curs_initscr(3X),