clear(3NCURSES) clear(3NCURSES)
NAME
erase, werase, clear, wclear, clrtobot, wclrtobot, clrtoeol, wclrtoeol
- clear all or part of a curses window
SYNOPSIS
#include <curses.h>
int erase(void);
int werase(WINDOW *win);
int clear(void);
int wclear(WINDOW *win);
int clrtobot(void);
int wclrtobot(WINDOW *win);
int clrtoeol(void);
int wclrtoeol(WINDOW *win);
DESCRIPTION
erase/werase
The erase and werase routines copy blanks to every position in the win-
dow, clearing the screen.
Blanks created by erasure have the current background rendition (as set
by wbkgdset(3X)) merged into them.
clear/wclear
The clear and wclear routines are like erase and werase, but they also
call clearok(3X), so that the screen is cleared completely on the next
call to wrefresh for that window and repainted from scratch.
clrtobot/wclrtobot
The clrtobot and wclrtobot routines erase from the cursor to the end of
screen. That is, they erase all lines below the cursor in the window.
Also, the current line to the right of the cursor, inclusive, is
erased.
clrtoeol/wclrtoeol
The clrtoeol and wclrtoeol routines erase the current line to the right
of the cursor, inclusive, to the end of the current line.
RETURN VALUE
All routines return the integer OK on success and ERR on failure.
X/Open defines no error conditions. In this implementation,
• functions using a window pointer parameter return an error if it is
null
• wclrtoeol returns an error if the cursor position is about to wrap.
NOTES
Note that erase, werase, clear, wclear, clrtobot, and clrtoeol may be
macros.
PORTABILITY
These functions are described in the XSI Curses standard, Issue 4. The
standard specifies that they return ERR on failure, but specifies no
error conditions.
The SVr4.0 manual says that these functions could return "a non-nega-
tive integer if immedok(3X) is set", referring to the return-value of
wrefresh. In that implementation, wrefresh would return a count of the
number of characters written to the terminal.
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.
This implementation, and others such as Solaris, sets the current posi-
tion to 0,0 after erasing via werase and wclear. That fact is not doc-
umented in other implementations, and may not be true of implementa-
tions which were not derived from SVr4 source.
Not obvious from the description, most implementations clear the screen
after wclear even for a subwindow or derived window. If you do not
want to clear the screen during the next wrefresh, use werase instead.
SEE ALSO
ncurses(3NCURSES), outopts(3NCURSES), refresh(3NCURSES), curses_vari-
ables(3NCURSES)
clear(3NCURSES)
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