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
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 insertion and deletion. This option should be
enabled only if the application 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 is not really needed. If insert/delete
line cannot be used, curses redraws the changed portions of all
If idcok is called with FALSE as second argument, curses no
longer considers 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., automatically cause a call to wrefresh. However, it
may degrade performance considerably, due to repeated calls to
wrefresh. It is disabled by default.
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 applications where the cursor is not used, since it
reduces the need for cursor motions.
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 character 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 terminal, it is also
necessary to call idlok).
The setscrreg and wsetscrreg routines allow the application
programmer to set a software scrolling region in a window. The
top and bot parameters 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
The functions setscrreg and wsetscrreg return OK upon success and
ERR upon failure. All other routines that return an integer
always return OK.
X/Open Curses does not define any error conditions.
In this implementation,
• those functions that have a window pointer will return an
error if the window pointer is null
• wsetscrreg returns an error if the scrolling region limits
extend outside the window.
X/Open does not define any error conditions. This implementation
returns an error if the window pointer is null.
These functions are described in the XSI Curses standard, Issue
From the outset, ncurses used nl/nonl to control the conversion
of newlines to carriage return/line-feed on output as well as
input. XSI Curses documents only the use of these functions for
input. This difference arose from converting the pcurses source
(which used ioctl calls with the sgttyb structure) to termios
(i.e., the POSIX terminal interface). In the former, both input
and output were controlled via a single option CRMOD, while the
latter separates these features. Because that conversion
interferes with output optimization, nl/nonl were amended after
ncurses 6.2 to eliminate their effect on output.
Some historic curses implementations had, as an undocumented
feature, the ability to do the equivalent of clearok(..., 1) by
saying touchwin(stdscr) or clear(stdscr). This will not work
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 time.
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 invisible.
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have
a bug report for this manual page, send it to
firstname.lastname@example.org. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2021-06-20. (At
that time, the date of the most recent commit that was found in
the repository was 2021-05-23.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to