ncurses 6.1 - patch 20190216

[ncurses.git] / man / curs_bkgd.3x

diff --git a/man/curs_bkgd.3x b/man/curs_bkgd.3x
index efd4f82763971d1d1e684db380497f9bed96ba18..d93bbd4a995e1b5e197033f2c6814db266e68d4c 100644 (file)
--- a/man/curs_bkgd.3x
+++ b/man/curs_bkgd.3x
@@ -1,5 +1,5 @@
 .\"***************************************************************************
 .\"***************************************************************************

-.\" Copyright (c) 1998,2000 Free Software Foundation, Inc.                   *
+.\" Copyright (c) 1998-2017,2018 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            *
 .\"                                                                          *
 .\" Permission is hereby granted, free of charge, to any person obtaining a  *
 .\" copy of this software and associated documentation files (the            *


@@ -26,77 +26,129 @@
 .\" authorization.                                                           *
 .\"***************************************************************************
 .\"
 .\" authorization.                                                           *
 .\"***************************************************************************
 .\"

-.\" $Id: curs_bkgd.3x,v 1.14 2000/07/01 17:39:31 tom Exp $
+.\" $Id: curs_bkgd.3x,v 1.28 2018/12/09 00:45:05 tom Exp $
+.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,
 .TH curs_bkgd 3X ""
 .SH NAME
 \fBbkgdset\fR, \fBwbkgdset\fR,
 \fBbkgd\fR, \fBwbkgd\fR,

-\fBgetbkgd\fR - \fBcurses\fR window background manipulation routines
-..
+\fBgetbkgd\fR \- \fBcurses\fR window background manipulation routines

 .SH SYNOPSIS
 \fB#include <curses.h>\fR
 .SH SYNOPSIS
 \fB#include <curses.h>\fR

-
-\fBvoid bkgdset(const chtype ch);\fR
+.PP
+\fBvoid bkgdset(chtype \fP\fIch\fP\fB);\fR

 .br
 .br

-\fBvoid wbkgdset(WINDOW *win, const chtype ch);\fR
+\fBvoid wbkgdset(WINDOW *\fP\fIwin, chtype \fP\fIch\fP\fB);\fR

 .br
 .br

-\fBint bkgd(const chtype ch);\fR
+\fBint bkgd(chtype \fP\fIch\fP\fB);\fR

 .br
 .br

-\fBint wbkgd(WINDOW *win, const chtype ch);\fR
+\fBint wbkgd(WINDOW *\fP\fIwin\fP\fB, chtype \fP\fIch\fP\fB);\fR

 .br
 .br

-\fBchtype getbkgd(WINDOW *win);\fR
+\fBchtype getbkgd(WINDOW *\fP\fIwin\fP\fB);\fR

 .br
 .br

-..

 .SH DESCRIPTION
 .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 attribute part of the background is combined (OR'ed) with all non-blank
 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 attribute part of the background is combined (OR'ed) with all non-blank

-characters that are written into the window with \fBwaddch\fR.  Both
-the character and attribute parts of the background are combined with
-the blank characters.  The background becomes a property of the
+characters that are written into the window with \fBwaddch\fR.
+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.
 character and moves with the character through any scrolling and
 insert/delete line/character operations.

-
-To the extent possible on a
-particular terminal, the attribute part of the background is displayed
+.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.
 as the graphic rendition of the character put on the screen.

-
+.SS bkgd
+.PP

 The \fBbkgd\fR and \fBwbkgd\fR functions
 set the background property of the current or specified window
 The \fBbkgd\fR and \fBwbkgd\fR functions
 set the background property of the current or specified window

-and then apply this setting to every character position in that window:
-
-.RS
+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 rendition of every character on the screen is changed to
 the new background rendition.

-
+.bP

 Wherever the former background character
 appears, it is changed to the new background character.
 Wherever the former background character
 appears, it is changed to the new background character.

-.RE
-
+.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:
+.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.
+.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.
+.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.
+.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 then adding attributes from the new background.
+.SS getbkgd
+.PP

 The \fBgetbkgd\fR function returns the given window's current background
 character/attribute pair.
 The \fBgetbkgd\fR function returns the given window's current background
 character/attribute pair.

-..

 .SH RETURN VALUE
 .SH RETURN VALUE

-The routines \fBbkgd\fR and \fBwbkgd\fR 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.
-..
+.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,
+but gives no failure conditions.
+.PP
+The routines \fBbkgd\fR and \fBwbkgd\fR return the integer \fBOK\fR,
+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",
+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
 .SH NOTES

+.PP

 Note that \fBbkgdset\fR and \fBbkgd\fR may be macros.
 Note that \fBbkgdset\fR and \fBbkgd\fR 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
 .SH PORTABILITY

-These functions are described in the XSI Curses standard, Issue 4.  The draft
-does not include \fBconst\fR qualifiers on the arguments.  The standard
-specifies that \fBbkgd\fR and \fBwbkgd\fR return \fBERR\fR, on failure. but
-gives no failure conditions.
-..
+.PP
+These functions are described in the XSI Curses standard, Issue 4
+(X/Open Curses).

 .SH SEE ALSO
 .SH SEE ALSO

-\fBcurses\fR(3X), \fBcurs_addch\fR(3X), \fBcurs_outopts\fR(3X)
-.\"#
-.\"# The following sets edit modes for GNU EMACS
-.\"# Local Variables:
-.\"# mode:nroff
-.\"# fill-column:79
-.\"# End:
+.na
+.PP
+\fBcurses\fR(3X),
+\fBcurs_addch\fR(3X),
+\fBcurs_attr\fR(3X),
+\fBcurs_outopts\fR(3X)