.\"***************************************************************************
-.\" Copyright 2018-2019,2020 Thomas E. Dickey *
+.\" Copyright 2018-2022,2023 Thomas E. Dickey *
.\" Copyright 1998-2015,2017 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" $Id: curs_bkgd.3x,v 1.31 2020/10/17 23:12:52 tom Exp $
+.\" $Id: curs_bkgd.3x,v 1.44 2023/09/16 23:34:43 tom Exp $
+.TH curs_bkgd 3X 2023-09-16 "ncurses 6.4" "Library calls"
.de bP
.ie n .IP \(bu 4
.el .IP \(bu 2
..
-.TH curs_bkgd 3X ""
.SH NAME
-\fBbkgdset\fR, \fBwbkgdset\fR,
-\fBbkgd\fR, \fBwbkgd\fR,
-\fBgetbkgd\fR \- \fBcurses\fR 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>\fR
+\fB#include <curses.h>\fP
.PP
-\fBvoid bkgdset(chtype \fP\fIch\fP\fB);\fR
+\fBvoid bkgdset(chtype \fIch\fB);\fR
.br
-\fBvoid wbkgdset(WINDOW *\fP\fIwin, chtype \fP\fIch\fP\fB);\fR
+\fBvoid wbkgdset(WINDOW *\fIwin, chtype \fIch\fB);\fR
.sp
-\fBint bkgd(chtype \fP\fIch\fP\fB);\fR
+\fBint bkgd(chtype \fIch\fB);\fR
.br
-\fBint wbkgd(WINDOW *\fP\fIwin\fP\fB, chtype \fP\fIch\fP\fB);\fR
+\fBint wbkgd(WINDOW *\fIwin\fB, chtype \fIch\fB);\fR
.sp
-\fBchtype getbkgd(WINDOW *\fP\fIwin\fP\fB);\fR
+\fBchtype getbkgd(WINDOW *\fIwin\fB);\fR
.br
.SH DESCRIPTION
.SS bkgdset
-The \fBbkgdset\fR and \fBwbkgdset\fR routines manipulate the
-background of the named window.
-The window background is a \fBchtype\fR consisting of
-any combination of attributes (i.e., rendition) and a character.
+The \fBbkgdset\fP and \fBwbkgdset\fP routines
+set the \fIbackground\fP for a window.
+A window's background is a \fBchtype\fP consisting of
+any combination of attributes (i.e., rendition) and a character:
+.bP
The attribute part of the background is combined (OR'ed) with all non-blank
-characters that are written into the window with \fBwaddch\fR.
+characters that are written into the window with \fBwaddch\fP.
+.bP
Both the character and attribute parts of the background are combined with
-the blank characters.
-The background becomes a property of the
+blank characters that are written into the window.
+.PP
+The background becomes a property of each
character and moves with the character through any scrolling and
insert/delete line/character operations.
.PP
the attribute part of the background is displayed
as the graphic rendition of the character put on the screen.
.SS bkgd
-.PP
-The \fBbkgd\fR and \fBwbkgd\fR functions
+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:
-.PP
.bP
The rendition of every character on the screen is changed to
the new background rendition.
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.
+.IP
+When \fBbkgdset\fP is used to set the background character,
+that does not update each cell in the window.
+A subsequent call to \fBbkgd\fP will only modify the \fIcharacter\fP in
+cells which match the current background character.
.bP
The library then checks if the cell uses color,
i.e., its color pair value is nonzero.
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
+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.
first removing those which 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.
+If the background's character value is zero (0), a space is assumed.
.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.
.SS getbkgd
-.PP
-The \fBgetbkgd\fR function returns the given window's current background
+The \fBgetbkgd\fP function returns the given window's current background
character/attribute pair.
.SH RETURN VALUE
-.PP
These functions are described in the XSI Curses standard, Issue 4.
-It specifies that \fBbkgd\fR and \fBwbkgd\fR return \fBERR\fR on failure,
+It specifies that \fBbkgd\fP and \fBwbkgd\fP return \fBERR\fP on failure,
but gives no failure conditions.
.PP
-The routines \fBbkgd\fR and \fBwbkgd\fR return the integer \fBOK\fR,
+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\fR and \fBwbkgd\fR may return \fBOK\fP
-"or a non-negative integer if \fBimmedok\fR is set",
+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.
.SH NOTES
-.PP
-Note that \fBbkgdset\fR and \fBbkgd\fR may be macros.
+Note that \fBbkgdset\fP and \fBbkgd\fP may be 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,
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).
.SH SEE ALSO
.na
-.PP
-\fBcurses\fR(3X),
-\fBcurs_addch\fR(3X),
-\fBcurs_attr\fR(3X),
-\fBcurs_outopts\fR(3X)
+\fBcurses\fP(3X),
+\fBcurs_addch\fP(3X),
+\fBcurs_attr\fP(3X),
+\fBcurs_outopts\fP(3X)
projects / ncurses.git / blobdiff