Manual Reference Pages - NONL (3)
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
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.
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
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.
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 lines.
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
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 setscrreg and wsetscrreg routines allow the application
programmer to set a software scrolling region in a window.
bot are the line numbers of the top and bottom margin of the scrolling
(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 character of the last
If disabled, (bf is FALSE), the cursor is left on the bottom
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 nl and nonl routines control whether the underlying display
device translates the return key into newline on input, and whether it
translates 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
Initially, these translations do occur.
If you disable 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
X/Open 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.
returns an error
if the cursor position is about to wrap.
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 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 programmer requesting
raw input wants a clean (ideally 8-bit clean) connection that the operating
system will not alter.
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 under
Earlier System V curses implementations specified that with scrollok
enabled, any window modification triggering a scroll also forced a physical
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 invisible.
Note that clearok, leaveok, scrollok, idcok, nl,
nonl and setscrreg may be macros.
The immedok routine is useful for windows that are used as terminal
curses(3X), curs_addch(3X), curs_clear(3X),
curs_initscr(3X), curs_scroll(3X), curs_refresh(3X)
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