NAME
clearok, idlok, idcok, immedok, leaveok, setscrreg, wsetscrreg, scrollok, nl, nonl - curses output options
SYNOPSIS
#include <curses.h>
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);
int nl(void);
int nonl(void);
DESCRIPTION
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(3X).
clearok
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.
idlok
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 lines.
idcok
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.
immedok
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.
leaveok
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.
setscrreg
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 output routines.)
scrollok
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).
nl, nonl
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 virtual screen). 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.
RETURN VALUE
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.
wclrtoeol
returns an error if the cursor position is about to wrap.
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.
PORTABILITY
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 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 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.
NOTES
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 emulators.
SEE ALSO
ncurses(3NCURSES), addch(3NCURSES), clear(3NCURSES), initscr(3NCURSES), scroll(3NCURSES), refresh(3NCURSES), curses_variables(3NCURSES).