'\" t
.\"***************************************************************************
-.\" Copyright (c) 1998-2015,2017 Free Software Foundation, Inc. *
+.\" Copyright (c) 1998-2018,2019 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_addch.3x,v 1.41 2017/05/05 18:15:29 tom Exp $
+.\" $Id: curs_addch.3x,v 1.47 2019/02/16 23:50:17 tom Exp $
.TH curs_addch 3X ""
.ie \n(.g .ds `` \(lq
.el .ds `` ``
.ie \n(.g .ds '' \(rq
.el .ds '' ''
.de bP
-.IP \(bu 4
+.ie n .IP \(bu 4
+.el .IP \(bu 2
..
.SH NAME
\fBaddch\fR,
.SS Adding characters
The \fBaddch\fR, \fBwaddch\fR, \fBmvaddch\fR and \fBmvwaddch\fR routines put
the character \fIch\fR into the given window at its current window position,
-which is then advanced. They are analogous to \fBputchar\fR(3) in \fBstdio\fR(3).
+which is then advanced.
+They are analogous to \fBputchar\fR(3) in \fBstdio\fR(3).
If the advance is at the right margin:
.bP
The cursor automatically wraps to the beginning of the next line.
The tab interval may be altered by setting the \fBTABSIZE\fR variable.
.PP
If \fIch\fR is any other control character, it
-is drawn in \fB^\fR\fIX\fR notation. Calling \fBwinch\fR after adding a
+is drawn in \fB^\fR\fIX\fR notation.
+Calling \fBwinch\fR after adding a
control character does not return the character itself, but instead returns
the ^-representation of the control character.
.PP
.PP
The \fBechochar\fR and \fBwechochar\fR routines are equivalent to a call to
\fBaddch\fR followed by a call to \fBrefresh\fR(3X), or a call to \fBwaddch\fR
-followed by a call to \fBwrefresh\fR. The knowledge that only a single
+followed by a call to \fBwrefresh\fR.
+The knowledge that only a single
character is being output is used and, for non-control characters, a
considerable performance gain may be seen by using these routines instead of
their equivalents.
.SS Line Graphics
The following variables may be used to add line drawing characters to the
-screen with routines of the \fBaddch\fR family. The default character listed
+screen with routines of the \fBaddch\fR family.
+The default character listed
below is used if the \fBacsc\fR capability does not define a terminal-specific
replacement for it,
or if the terminal and locale configuration requires Unicode but the
.SH PORTABILITY
All these functions are described in the XSI Curses standard, Issue 4.
The defaults specified for forms-drawing characters apply in the POSIX locale.
+.SS ACS Symbols
.LP
X/Open Curses states that the \fIACS_\fP definitions are \fBchar\fP constants.
For the wide-character implementation (see \fBcurs_add_wch\fP),
ACS_NEQUAL,
ACS_STERLING)
were not documented in
-any publicly released System V. However, many publicly available terminfos
+any publicly released System V.
+However, many publicly available terminfos
include \fBacsc\fR strings in which their key characters (pryz{|}) are
embedded, and a second-hand list of their character descriptions has come
-to light. The ACS-prefixed names for them were invented for \fBncurses\fR(3X).
+to light.
+The ACS-prefixed names for them were invented for \fBncurses\fR(3X).
.LP
The \fIdisplayed\fP values for the \fIACS_\fP and \fIWACS_\fP constants
depend on
In certain cases, the terminal is unable to display line-drawing characters
except by using UTF-8 (see the discussion of \fBNCURSES_NO_UTF8_ACS\fP in
ncurses(3X)).
+.SS Character Set
+X/Open Curses assumes that the parameter passed to \fBwaddch\fP contains
+a single character.
+As discussed in \fBcurs_attr\fP(3X), that character may have been
+more than eight bits in an SVr3 or SVr4 implementation,
+but in the X/Open Curses model, the details are not given.
+The important distinction between SVr4 curses and X/Open Curses is
+that the non-character information (attributes and color) was
+separated from the character information which is packed in a \fBchtype\fP
+to pass to \fBwaddch\fP.
+.PP
+In this implementation, \fBchtype\fP holds eight bits.
+But ncurses allows multibyte characters to be passed in a succession
+of calls to \fBwaddch\fP.
+The other implementations do not do this;
+a call to \fBwaddch\fP passes exactly one character
+which may be rendered as one or more cells on the screen
+depending on whether it is printable.
+.PP
+Depending on the locale settings,
+ncurses will inspect the byte passed in each call to \fBwaddch\fP,
+and check if the latest call will continue a multibyte sequence.
+When a character is \fIcomplete\fP,
+ncurses displays the character and moves to the next position in the screen.
+.PP
+If the calling application interrupts the succession of bytes in
+a multibyte character by moving the current location (e.g., using \fBwmove\fP),
+ncurses discards the partially built character,
+starting over again.
+.PP
+For portability to other implementations,
+do not rely upon this behavior:
+.bP
+check if a character can be represented as a single byte in the current locale
+before attempting call \fBwaddch\fP, and
+.bP
+call \fBwadd_wch\fP for characters which cannot be handled by \fBwaddch\fP.
+.SS TABSIZE
.LP
-The \fBTABSIZE\fR variable is implemented in some versions of curses,
-but is not part of X/Open curses.
+The \fBTABSIZE\fR variable is implemented in SVr4 and other versions of curses,
+but is not part of X/Open curses
+(see \fBcurs_variables\fR(3X) for more details).
.LP
If \fIch\fR is a carriage return,
the cursor is moved to the beginning of the current row of the window.
projects / ncurses.git / blobdiff