curs_clear
Section: Library calls (3X)
Updated: 202-0-18
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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,
.IP * 4
functions using a window pointer parameter return
ERR
if it is null
.IP * 4
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 no-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)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- erase, werase
-
- clear, wclear
-
- clrtobot, wclrtobot
-
- clrtoeol, wclrtoeol
-
- RETURN VALUE
-
- NOTES
-
- PORTABILITY
-
- SEE ALSO
-
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