Ubuntu Manpage: clearok, idlok, idcok, immedok, leaveok, setscrreg, wsetscrreg, scrollok

Provided by: ncurses-doc_6.4+20240113-1ubuntu2_all

NAME

       clearok, idlok, idcok, immedok, leaveok, setscrreg, wsetscrreg, scrollok - set 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 scrollok(WINDOW *win, bool bf);

       int setscrreg(int top, int bot);
       int wsetscrreg(WINDOW *win, int top, int bot);

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(3NCURSES).

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 second argument, any change in the window image, such as the ones
caused by waddch, wclrtobot, wscrl, etc., automatically causes a call to wrefresh. However, it may
degrade performance considerably, due to repeated calls to wrefresh. Calling immedok with FALSE as
second argument restores the default behavior, i.e., deferring screen updates until a refresh is needed.

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.

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).

setscrreg, wsetscrreg
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.)

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

       •   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.

NOTES

       Note that clearok, leaveok, scrollok, idcok, and setscrreg may be macros.

       The immedok routine is useful for windows that are used as terminal emulators.

PORTABILITY

These functions are described in the XSI Curses standard, Issue 4.

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 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.