137 lines
5.5 KiB
Groff
137 lines
5.5 KiB
Groff
.\" $OpenBSD: curs_clear.3,v 1.8 2023/10/17 09:52:08 nicm Exp $
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.\"
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.\"***************************************************************************
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.\" Copyright 2018-2022,2023 Thomas E. Dickey *
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.\" Copyright 1998-2010,2016 Free Software Foundation, Inc. *
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.\" *
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.\" Permission is hereby granted, free of charge, to any person obtaining a *
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.\" copy of this software and associated documentation files (the *
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.\" "Software"), to deal in the Software without restriction, including *
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.\" without limitation the rights to use, copy, modify, merge, publish, *
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.\" distribute, distribute with modifications, sublicense, and/or sell *
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.\" copies of the Software, and to permit persons to whom the Software is *
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.\" furnished to do so, subject to the following conditions: *
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.\" *
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.\" The above copyright notice and this permission notice shall be included *
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.\" in all copies or substantial portions of the Software. *
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.\" *
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.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
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.\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
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.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
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.\" IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
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.\" DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
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.\" OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
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.\" THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
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.\" *
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.\" Except as contained in this notice, the name(s) of the above copyright *
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.\" holders shall not be used in advertising or otherwise to promote the *
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.\" sale, use or other dealings in this Software without prior written *
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.\" authorization. *
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.\"***************************************************************************
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.\"
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.\" $Id: curs_clear.3,v 1.8 2023/10/17 09:52:08 nicm Exp $
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.TH curs_clear 3 2023-07-01 "ncurses 6.4" "Library calls"
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.na
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.hy 0
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.de bP
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.ie n .IP \(bu 4
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.el .IP \(bu 2
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..
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.SH NAME
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\fBerase\fP,
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\fBwerase\fP,
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\fBclear\fP,
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\fBwclear\fP,
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\fBclrtobot\fP,
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\fBwclrtobot\fP,
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\fBclrtoeol\fP,
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\fBwclrtoeol\fP \- clear all or part of a \fBcurses\fP window
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.ad
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.hy
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.SH SYNOPSIS
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\fB#include <curses.h>\fP
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.sp
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\fBint erase(void);\fP
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.br
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\fBint werase(WINDOW *\fIwin\fB);\fR
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.sp
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\fBint clear(void);\fP
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.br
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\fBint wclear(WINDOW *\fIwin\fB);\fR
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.sp
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\fBint clrtobot(void);\fP
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.br
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\fBint wclrtobot(WINDOW *\fIwin\fB);\fR
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.sp
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\fBint clrtoeol(void);\fP
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.br
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\fBint wclrtoeol(WINDOW *\fIwin\fB);\fR
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.SH DESCRIPTION
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.SS erase/werase
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The \fBerase\fP and \fBwerase\fP routines copy blanks to every
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position in the window, clearing the screen.
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.PP
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Blanks created by erasure have the current background rendition (as set
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by \fBwbkgdset\fP(3)) merged into them.
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.SS clear/wclear
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The \fBclear\fP and \fBwclear\fP routines are like \fBerase\fP and
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\fBwerase\fP, but they also call \fBclearok\fP(3), so that the screen is
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cleared completely on the next call to \fBwrefresh\fP for that window
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and repainted from scratch.
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.SS clrtobot/wclrtobot
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The \fBclrtobot\fP and \fBwclrtobot\fP routines erase from the cursor to the
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end of screen.
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That is, they erase all lines below the cursor in the window.
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Also, the current line to the right of the cursor, inclusive, is erased.
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.SS clrtoeol/wclrtoeol
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The \fBclrtoeol\fP and \fBwclrtoeol\fP routines erase the current line
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to the right of the cursor, inclusive, to the end of the current line.
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.SH RETURN VALUE
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All routines return the integer \fBOK\fP on success and \fBERR\fP on failure.
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.PP
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X/Open defines no error conditions.
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In this implementation,
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.bP
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functions using a window pointer parameter return an error if it is null
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.bP
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\fBwclrtoeol\fP returns an error
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if the cursor position is about to wrap.
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.SH NOTES
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Note that \fBerase\fP, \fBwerase\fP, \fBclear\fP, \fBwclear\fP,
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\fBclrtobot\fP, and \fBclrtoeol\fP may be macros.
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.SH PORTABILITY
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These functions are described in the XSI Curses standard, Issue 4.
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The
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standard specifies that they return \fBERR\fP on failure, but specifies no
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error conditions.
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.PP
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The SVr4.0 manual says that these functions could
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return "a non-negative integer if \fBimmedok\fP(3) is set",
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referring to the return-value of \fBwrefresh\fP.
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In that implementation, \fBwrefresh\fP would return a count of
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the number of characters written to the terminal.
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.PP
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Some historic curses implementations had, as an undocumented feature, the
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ability to do the equivalent of \fBclearok(..., 1)\fP by saying
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\fBtouchwin(stdscr)\fP or \fBclear(stdscr)\fP.
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This will not work under
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ncurses.
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.PP
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This implementation, and others such as Solaris,
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sets the current position to 0,0 after erasing
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via \fBwerase\fP and \fBwclear\fP.
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That fact is not documented in other implementations,
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and may not be true of implementations
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which were not derived from SVr4 source.
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.PP
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Not obvious from the description,
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most implementations clear the screen after \fBwclear\fP
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even for a subwindow or derived window.
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If you do not want to clear the screen during the next \fBwrefresh\fP,
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use \fBwerase\fP instead.
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.SH SEE ALSO
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\fBcurses\fP(3),
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\fBcurs_outopts\fP(3),
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\fBcurs_refresh\fP(3),
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\fBcurs_variables\fP(3)
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