.\"***************************************************************************
-.\" Copyright (c) 1998 Free Software Foundation, Inc. *
+.\" Copyright 2018-2020,2021 Thomas E. Dickey *
+.\" Copyright 1998-2010,2016 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" copy of this software and associated documentation files (the *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" $Id: curs_clear.3x,v 1.7 1998/03/11 21:12:53 juergen Exp $
+.\" $Id: curs_clear.3x,v 1.22 2021/12/25 21:41:58 tom Exp $
.TH curs_clear 3X ""
+.na
+.hy 0
+.de bP
+.ie n .IP \(bu 4
+.el .IP \(bu 2
+..
.SH NAME
-\fBerase\fR, \fBwerase\fR, \fBclear\fR,
-\fBwclear\fR, \fBclrtobot\fR, \fBwclrtobot\fR, \fBclrtoeol\fR,
-\fBwclrtoeol\fR - clear all or part of a \fBcurses\fR window
+\fBerase\fP,
+\fBwerase\fP,
+\fBclear\fP,
+\fBwclear\fP,
+\fBclrtobot\fP,
+\fBwclrtobot\fP,
+\fBclrtoeol\fP,
+\fBwclrtoeol\fP \- clear all or part of a \fBcurses\fP window
+.ad
+.hy
.SH SYNOPSIS
-\fB# include <curses.h>\fR
-
-\fBint erase(void);\fR
+\fB#include <curses.h>\fP
+.sp
+\fBint erase(void);\fP
.br
-\fBint werase(WINDOW *win);\fR
+\fBint werase(WINDOW *\fP\fIwin\fP\fB);\fP
+.sp
+\fBint clear(void);\fP
.br
-\fBint clear(void);\fR
+\fBint wclear(WINDOW *\fP\fIwin\fP\fB);\fP
+.sp
+\fBint clrtobot(void);\fP
.br
-\fBint wclear(WINDOW *win);\fR
+\fBint wclrtobot(WINDOW *\fP\fIwin\fP\fB);\fP
+.sp
+\fBint clrtoeol(void);\fP
.br
-\fBint clrtobot(void);\fR
-.br
-\fBint wclrtobot(WINDOW *win);\fR
-.br
-\fBint clrtoeol(void);\fR
-.br
-\fBint wclrtoeol(WINDOW *win);\fR
+\fBint wclrtoeol(WINDOW *\fP\fIwin\fP\fB);\fP
.br
.SH DESCRIPTION
-The \fBerase\fR and \fBwerase\fR routines copy blanks to every
+The \fBerase\fP and \fBwerase\fP routines copy blanks to every
position in the window, clearing the screen.
-
-The \fBclear\fR and \fBwclear\fR routines are like \fBerase\fR and
-\fBwerase\fR, but they also call \fBclearok\fR, so that the screen is
-cleared completely on the next call to \fBwrefresh\fR for that window
+.PP
+The \fBclear\fP and \fBwclear\fP routines are like \fBerase\fP and
+\fBwerase\fP, but they also call \fBclearok\fP, so that the screen is
+cleared completely on the next call to \fBwrefresh\fP for that window
and repainted from scratch.
-
-The \fBclrtobot\fR and \fBwclrtobot\fR routines erase from the cursor to the
-end of screen. That is, they erase all lines below the cursor in the window.
+.PP
+The \fBclrtobot\fP and \fBwclrtobot\fP 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.
-
-The \fBclrtoeol\fR and \fBwclrtoeol\fR routines erase the current line
+.PP
+The \fBclrtoeol\fP and \fBwclrtoeol\fP routines erase the current line
to the right of the cursor, inclusive, to the end of the current line.
-
+.PP
Blanks created by erasure have the current background rendition (as set
-by \fBwbkgdset\fR) merged into them.
+by \fBwbkgdset\fP) merged into them.
.SH RETURN VALUE
-All routines return the integer \fBOK\fR. The SVr4.0 manual says "or a
-non-negative integer if \fBimmedok\fR is set", but this appears to be an error.
+All routines return the integer \fBOK\fP on success and \fBERR\fP on failure.
+.PP
+X/Open defines no error conditions.
+In this implementation,
+.bP
+functions using a window pointer parameter return an error if it is null
+.bP
+\fBwclrtoeol\fP returns an error
+if the cursor position is about to wrap.
.SH NOTES
-Note that \fBerase\fR, \fBwerase\fR, \fBclear\fR, \fBwclear\fR,
-\fBclrtobot\fR, and \fBclrtoeol\fR may be macros.
+Note that \fBerase\fP, \fBwerase\fP, \fBclear\fP, \fBwclear\fP,
+\fBclrtobot\fP, and \fBclrtoeol\fP may be macros.
.SH PORTABILITY
-These functions are described in the XSI Curses standard, Issue 4. The
-standard specifies that they return \fBERR\fR on failure, but specifies no
+These functions are described in the XSI Curses standard, Issue 4.
+The
+standard specifies that they return \fBERR\fP on failure, but specifies no
error conditions.
-
+.PP
+The SVr4.0 manual says that these functions could
+return "a non-negative integer if \fBimmedok\fP is set",
+referring to the return-value of \fBwrefresh\fP.
+In that implementation, \fBwrefresh\fP would return a count of
+the number of characters written to the terminal.
+.PP
Some historic curses implementations had, as an undocumented feature, the
-ability to do the equivalent of \fBclearok(..., 1)\fR by saying
-\fBtouchwin(stdscr)\fR or \fBclear(stdscr)\fR. This will not work under
+ability to do the equivalent of \fBclearok(..., 1)\fP by saying
+\fBtouchwin(stdscr)\fP or \fBclear(stdscr)\fP.
+This will not work under
ncurses.
+.PP
+This implementation, and others such as Solaris,
+sets the current position to 0,0 after erasing
+via \fBwerase\fP and \fBwclear\fP.
+That fact is not documented in other implementations,
+and may not be true of implementations
+which were not derived from SVr4 source.
+.PP
+Not obvious from the description,
+most implementations clear the screen after \fBwclear\fP
+even for a subwindow or derived window.
+If you do not want to clear the screen during the next \fBwrefresh\fP,
+use \fBwerase\fP instead.
.SH SEE ALSO
-\fBcurses\fR(3X), \fBcurs_outopts\fR(3X), \fBcurs_refresh\fR(3X)
-.\"#
-.\"# The following sets edit modes for GNU EMACS
-.\"# Local Variables:
-.\"# mode:nroff
-.\"# fill-column:79
-.\"# End:
+\fBcurses\fP(3X),
+\fBcurs_outopts\fP(3X),
+\fBcurs_refresh\fP(3X),
+\fBcurs_variables\fP(3X)
projects / ncurses.git / blobdiff