.\"***************************************************************************
-.\" Copyright (c) 2010 Free Software Foundation, Inc. *
+.\" Copyright (c) 2010-2018,2019 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_variables.3x,v 1.3 2010/09/11 20:16:49 tom Exp $
+.\" $Id: curs_variables.3x,v 1.13 2019/06/01 22:51:21 tom Exp $
.TH curs_variables 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
..
.ds n 5
.na
A more complete description is given in the \fBcurses\fP(3X) manual page.
.PP
Depending on the configuration, these may be actual variables,
-or macros (see \fBcurs_threads\fR(3X))
+or macros (see \fBcurs_threads\fR(3X) and \fBcurs_opaque\fR(3X))
which provide read-only access to \fIcurses\fP's state.
In either case, applications should treat them as read-only to avoid
confusing the library.
escape character,
to distinguish between an individual escape character entered on the
keyboard from escape sequences sent by cursor- and function-keys
-(see curses(3X).
+(see curses(3X)).
.SS LINES
After initializing curses, this variable contains the height of the screen,
i.e., the number of lines.
.SS The Current Screen
This implementation of curses uses a special window \fBcurscr\fP to
record its updates to the terminal screen.
+.PP
+This is referred to as the \*(``physical screen\*('' in the
+\fBcurs_refresh\fR(3X) and
+\fBcurs_outopts\fR(3X) manual pages.
.SS The New Screen
This implementation of curses uses a special window \fBnewscr\fP to
hold updates to the terminal screen before applying them to \fBcurscr\fP.
+.PP
+This is referred to as the \*(``virtual screen\*('' in the
+\fBcurs_kernel\fR(3X),
+\fBcurs_refresh\fR(3X) and
+\fBcurs_outopts\fR(3X) manual pages.
.SS The Standard Screen
Upon initializing curses,
a default window called \fBstdscr\fP,
If \fBcurses\fP is configured to use separate curses/terminfo libraries,
most of these variables reside in the curses library.
.SH PORTABILITY
-ESCDELAY and TABSIZE are extensions,
-not provided in most other implementations of curses.
+\fBTABSIZE\fP is a feature of SVr4 curses
+which is not documented by X/Open curses.
+.bP
+In SVr4 curses, \fBTABSIZE\fP is initially set from the terminal description's
+\fBinit_tabs\fP capability.
+After that, it can be altered by the applications using SVr4 curses.
+.IP
+SVr4 curses uses the current value of \fBTABSIZE\fP to
+compute the position of tabstops for updating both
+the virtual screen with \fBaddch\fP(3X) as well as
+the physical screen with \fBmvcur\fP(3X).
+.bP
+This implementation uses the current value of \fBTABSIZE\fP only for
+updating the virtual screen.
+It uses the terminal description's \fBit\fP (\fBinit_tabs\fP) capability for
+computing hardware tabs (i.e., tab stops on the physical screen).
+.bP
+Other implementations differ.
+For instance, NetBSD curses allows \fBTABSIZE\fP to be set through
+an environment variable.
+This implementation does not.
+.IP
+NetBSD curses does not support hardware tabs;
+it uses the \fBinit_tabs\fP capability and the \fBTABSIZE\fP variable
+only for updating the virtual screen.
+.PP
+\fBESCDELAY\fP is an extension in AIX curses:
+.bP
+In AIX, the units for \fBESCDELAY\fP are \fIfifths\fP of a millisecond.
+.bP
+The default value for AIX's \fBESCDELAY\fP is 0.1 seconds.
+.bP
+AIX also enforces a limit of 10,000 seconds for \fBESCDELAY\fP;
+this implementation currently has no upper limit.
+.PP
+This implementation has long used \fBESCDELAY\fP with units of milliseconds,
+making it impossible to be completely compatible with AIX.
+Likewise, most users have either decided to override the value,
+or rely upon its default value.
.SH SEE ALSO
\fBcurses\fR(3X),
+\fBcurs_opaque\fR(3X),
+\fBcurs_terminfo\fR(3X),
\fBcurs_threads\fR(3X),
\fBterm_variables\fR(3X),
-\fBterminfo\fR(3X),
\fBterminfo\fR(\*n).
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