clearok
curs_outopts(3X) curs_outopts(3X)
NAME
clearok, idlok, idcok, immedok, leaveok, setscrreg, wsetscrreg, scrol-
lok, 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.
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 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
considers using the hardware insert/delete character feature of termi-
nals 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 per-
formance considerably, due to repeated calls to wrefresh. It is dis-
abled 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 appli-
cations 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. 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 out-
put 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 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 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.
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.
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 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 wre-
fresh 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
curses(3X), curs_addch(3X), curs_clear(3X), curs_initscr(3X),
curs_scroll(3X), curs_refresh(3X)
curs_outopts(3X)
