X-Git-Url: https://ncurses.scripts.mit.edu/?a=blobdiff_plain;f=man%2Fcurs_bkgd.3x;h=25ba1f9f72c8b2e5c99257a5090be8341af6f7f6;hb=00dd248b527ad47f0fc3b0776a0889da0ac926d0;hp=2c3d3d4fee93d8663cfa031a4c06927e3d14107e;hpb=16fbf3f4f7d96b6ee6bf9159b22f26e05962aa3d;p=ncurses.git

diff --git a/man/curs_bkgd.3x b/man/curs_bkgd.3x
index 2c3d3d4f..25ba1f9f 100644
--- a/man/curs_bkgd.3x
+++ b/man/curs_bkgd.3x
@@ -1,5 +1,5 @@
 .\"***************************************************************************
-.\" Copyright 2018-2021,2022 Thomas E. Dickey                                *
+.\" Copyright 2018-2023,2024 Thomas E. Dickey                                *
 .\" Copyright 1998-2015,2017 Free Software Foundation, Inc.                  *
 .\"                                                                          *
 .\" Permission is hereby granted, free of charge, to any person obtaining a  *
@@ -27,135 +27,200 @@
 .\" authorization.                                                           *
 .\"***************************************************************************
 .\"
-.\" $Id: curs_bkgd.3x,v 1.34 2022/02/12 20:06:41 tom Exp $
+.\" $Id: curs_bkgd.3x,v 1.61 2024/04/20 18:54:36 tom Exp $
+.TH curs_bkgd 3X 2024-04-20 "ncurses @NCURSES_MAJOR@.@NCURSES_MINOR@" "Library calls"
+.ie \n(.g \{\
+.ds `` \(lq
+.ds '' \(rq
+.\}
+.el \{\
+.ie t .ds `` ``
+.el   .ds `` ""
+.ie t .ds '' ''
+.el   .ds '' ""
+.\}
+.
 .de bP
 .ie n  .IP \(bu 4
 .el    .IP \(bu 2
 ..
-.TH curs_bkgd 3X ""
 .SH NAME
-\fBbkgdset\fP, \fBwbkgdset\fP,
-\fBbkgd\fP, \fBwbkgd\fP,
-\fBgetbkgd\fP \- \fBcurses\fP window background manipulation routines
+\fB\%bkgdset\fP,
+\fB\%wbkgdset\fP,
+\fB\%bkgd\fP,
+\fB\%wbkgd\fP,
+\fB\%getbkgd\fP \-
+manipulate background of a \fIcurses\fR window of characters
 .SH SYNOPSIS
-\fB#include <curses.h>\fP
-.PP
-\fBvoid bkgdset(chtype \fIch\fB);\fR
-.br
-\fBvoid wbkgdset(WINDOW *\fIwin, chtype \fIch\fB);\fR
-.sp
-\fBint bkgd(chtype \fIch\fB);\fR
-.br
-\fBint wbkgd(WINDOW *\fIwin\fB, chtype \fIch\fB);\fR
-.sp
-\fBchtype getbkgd(WINDOW *\fIwin\fB);\fR
-.br
-.SH DESCRIPTION
-.SS bkgdset
-The \fBbkgdset\fP and \fBwbkgdset\fP routines manipulate the
-background of the named window.
-The window background is a \fBchtype\fP consisting of
-any combination of attributes (i.e., rendition) and a character.
-The attribute part of the background is combined (OR'ed) with all non-blank
-characters that are written into the window with \fBwaddch\fP.
-Both the character and attribute parts of the background are combined with
-the blank characters.
-The background becomes a property of the
-character and moves with the character through any scrolling and
-insert/delete line/character operations.
-.PP
-To the extent possible on a particular terminal,
-the attribute part of the background is displayed
-as the graphic rendition of the character put on the screen.
-.SS bkgd
-.PP
-The \fBbkgd\fP and \fBwbkgd\fP functions
-set the background property of the current or specified window
-and then apply this setting to every character position in that window.
-According to X/Open Curses, it should do this:
+.nf
+\fB#include <curses.h>
+.PP
+\fBint bkgd(chtype \fIch\fP);
+\fBint wbkgd(WINDOW *\fIwin\fP, chtype \fIch\fP);
+.PP
+\fBvoid bkgdset(chtype \fIch\fP);
+\fBvoid wbkgdset(WINDOW *\fIwin\fP, chtype \fIch\fP);
 .PP
+\fBchtype getbkgd(WINDOW *\fIwin\fP);
+.fi
+.SH DESCRIPTION
+The
+.I background
+of a
+.I curses
+window
+(in the library's non-\*(``wide\*('' configuration)
+is a
+.I \%chtype
+combining a set of attributes
+(see \fB\%curs_attr\fP(3X))
+with a character called the
+.I "blank character."
+.PP
+The blank character is a spacing character that populates a window's
+character cells when their contents are erased without replacement.
+The background's attributes are combined with all non-blank characters
+written to the window,
+as with the \fB\%waddch\fP(3X) and \fB\%winsch\fP(3X) families of
+functions.
+.PP
+The blank character and attributes of the background combine with
+characters written to the window as described below.
+The background becomes a property of the character and moves with it
+through any scrolling and insert/delete line/character operations.
+.PP
+To the extent possible on a given terminal,
+the attribute part of the background is displayed as the graphic
+rendition of the character put on the screen.
+.SS "bkgd, wbkgd"
+\fB\%bkgd\fP and \fB\%wbkgd\fP set the background property of
+\fB\%stdscr\fP or the specified window and then apply this setting to
+every character cell in that window.
 .bP
-The rendition of every character on the screen is changed to
-the new background rendition.
+The rendition of every character in the window changes to the new
+background rendition.
 .bP
-Wherever the former background character
-appears, it is changed to the new background character.
-.PP
-Neither X/Open Curses nor the SVr4 manual pages give details about
-the way the rendition of characters on the screen is updated when
-\fBbkgd\fP or \fBwbkgd\fP is used to change the background character.
-.PP
-This implementation, like SVr4 curses, does not store the background
-and window attribute contributions to each cell separately.
-It updates the rendition by comparing the character, non-color attributes and
-colors contained in the background.
-For each cell in the window, whether or not it is blank:
+Wherever the former background character appears,
+it changes to the new background character.
+.PP
+.I \%ncurses
+updates the rendition of each character cell by comparing the character,
+non-color attributes,
+and colors.
+The library applies to following procedure to each cell in the window,
+whether or not it is blank.
 .bP
-The library first compares the \fIcharacter\fP,
-and if it matches the current character part of the background,
-it replaces that with the new background character.
+.I \%ncurses
+first compares the cell's character to the previously specified blank
+character;
+if they match,
+.I \%ncurses
+writes the new blank character to the cell.
 .bP
-The library then checks if the cell uses color,
-i.e., its color pair value is nonzero.
-If not, it simply replaces the attributes and color pair in the
-cell with those from the new background character.
+.I \%ncurses
+then checks if the cell uses color,
+that is,
+its color pair value is nonzero.
+If not,
+it simply replaces the attributes and color pair in the cell with those
+from the new background character.
 .bP
 If the cell uses color,
-and that matches the color in the current background,
-the library removes attributes
-which may have come from the current background
-and adds attributes from the new background.
-It finishes by setting the cell
-to use the color from the new background.
+and its background color matches that of the current window background,
+.I \%ncurses
+removes attributes that may have come from the current background and
+adds those from the new background.
+It finishes by setting the cell's background to use the new window
+background color.
 .bP
 If the cell uses color,
-and that does not match the color in the current background,
-the library updates only the non-color attributes,
-first removing those which may have come from the current background,
+and its background color does not match that of the current window
+background,
+.I \%ncurses
+updates only the non-color attributes,
+first removing those that may have come from the current background,
 and then adding attributes from the new background.
 .PP
-If the background's character value is zero, a space is assumed.
+.I \%ncurses
+treats a background character value of zero (0) as a blank character.
 .PP
 If the terminal does not support color,
-or if color has not been started with \fBstart_color\fP,
-the new background character's color attribute will be ignored.
+or if color has not been initialized with \fB\%start_color\fP(3X),
+.I \%ncurses
+ignores the new background character's color attribute.
+.SS "bkgdset, wbkgdset"
+\fB\%bkgdset\fP and \fB\%wbkgdset\fP manipulate the background of
+the applicable window,
+without updating the character cells as \fB\%bkgd\fP and
+\fB\%wbkgd\fP do;
+only future writes reflect the updated background.
 .SS getbkgd
-.PP
-The \fBgetbkgd\fP function returns the given window's current background
-character/attribute pair.
+\fB\%getbkgd\fP obtains the given window's background character and
+attribute combination.
 .SH RETURN VALUE
+Functions returning an \fIint\fP return \fBOK\fP on success.
+\fB\%bkgd\fP returns \fBERR\fP if the library has not been initialized.
+\fB\%wbkgd\fP and \fB\%getbkgd\fP return \fBERR\fP if a \fI\%WINDOW\fP
+pointer argument is null.
 .PP
-These functions are described in the XSI Curses standard, Issue 4.
-It specifies that \fBbkgd\fP and \fBwbkgd\fP return \fBERR\fP on failure,
-but gives no failure conditions.
+\fB\%bkgdset\fP and \fBwbkgdset\fP do not return a value.
 .PP
-The routines \fBbkgd\fP and \fBwbkgd\fP return the integer \fBOK\fP,
-unless the library has not been initialized.
-.PP
-In contrast,
-the SVr4.0 manual says \fBbkgd\fP and \fBwbkgd\fP may return \fBOK\fP
-"or a non-negative integer if \fBimmedok\fP is set",
-which refers to the return value from \fBwrefresh\fP
-(used to implement the immediate repainting).
-The SVr4 curses \fBwrefresh\fP returns the number of characters
-written to the screen during the refresh.
-This implementation does not do that.
+\fB\%getbkgd\fP returns a window's background character and attribute
+combination.
 .SH NOTES
+Unusually,
+there is no \fB\%wgetbkgd\fP function;
+\fB\%getbkgd\fP behaves as one would expect \fB\%wgetbkgd\fP to,
+accepting a \fI\%WINDOW\fP pointer argument.
 .PP
-Note that \fBbkgdset\fP and \fBbkgd\fP may be macros.
+\fB\%bkgd\fP and
+\fB\%bkgdset\fP
+may be implemented as macros.
 .PP
 X/Open Curses mentions that the character part of the background must
 be a single-byte value.
-This implementation, like SVr4, checks to ensure that,
+\fI\%ncurses\fP,
+like SVr4 \fIcurses\fP,
+checks to ensure that,
 and will reuse the old background character if the check fails.
 .SH PORTABILITY
-.PP
-These functions are described in the XSI Curses standard, Issue 4
-(X/Open Curses).
+X/Open Curses,
+Issue 4 describes these functions.
+It specifies that
+\fB\%bkgd\fP,
+\fB\%wbkgd\fP,
+and
+\fB\%getbkgd\fP
+return \fBERR\fP on failure
+(in the case of the last,
+this value is cast to
+.IR \%chtype ),
+but describes no failure conditions.
+.PP
+The SVr4.0 manual says that \fB\%bkgd\fP and \fB\%wbkgd\fP may return
+\fBOK\fP
+\*(``or a non-negative integer if \fB\%immedok\fP is set\*('',
+which refers to the return value from \fB\%wrefresh\fP(3X),
+used to implement the immediate repainting.
+SVr4 \fIcurses\fP's \fB\%wrefresh\fP returns the number of characters
+written to the screen during the refresh.
+\fI\%ncurses\fP does not do that.
+.PP
+Neither X/Open Curses nor the SVr4 manual pages detail how the rendition
+of characters on the screen updates when \fB\%bkgd\fP or \fB\%wbkgd\fP
+changes the background character.
+.IR \%ncurses ,
+like SVr4
+.IR curses ,
+does not
+(in its non-\*(``wide\*('' configuration)
+store the background and window attribute contributions to each
+character cell separately.
 .SH SEE ALSO
-.na
+\fB\%curs_bkgrnd\fP(3X) describes the corresponding functions in the
+\*(``wide\*('' configuration of
+.IR \%ncurses .
 .PP
-\fBcurses\fP(3X),
-\fBcurs_addch\fP(3X),
-\fBcurs_attr\fP(3X),
-\fBcurs_outopts\fP(3X)
+\fB\%curses\fP(3X),
+\fB\%curs_addch\fP(3X),
+\fB\%curs_attr\fP(3X)