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.