clearok(3ncurses)
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.
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). outopts(3NCURSES)
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