curs_clear(3X)

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 window, 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.

In this implementation, functions using a window pointer parameter return ERR if it is null wclrtoeol returns an error if the cursor position is about to wrap.

NOTES
erase, werase, clear, wclear, clrtobot, and clrtoeol may be implemented as macros.

PORTABILITY
X/Open Curses Issue 4 describes these functions. It specifies no error conditions for them.

SVr4 documentation says that these functions return OK “or a non-negative integer if immedok() is set”, referring to the return value from wrefresh, which in SVr4 returns a count of characters written to the window if its immedok property is set; in ncurses, it does not.

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.

This implementation, and others such as Solaris, sets the current position to 0,0 after erasing via werase and wclear. That fact is not documented in other implementations, and may not be true of implementations 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
curses(3X), curs_outopts(3X), curs_refresh(3X), curs_variables(3X)