ncurses 6.1 - patch 20191005

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

diff --git a/man/curs_variables.3x b/man/curs_variables.3x
index 952ececa0ad862a95474bb29a0dc4a1ca4d6f995..5d7de8c61553082099230fbb52c390ed954f613c 100644 (file)
--- a/man/curs_variables.3x
+++ b/man/curs_variables.3x
@@ -1,5 +1,5 @@
 .\"***************************************************************************
-.\" Copyright (c) 2010,2013 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            *
@@ -26,10 +26,15 @@
 .\" authorization.                                                           *
 .\"***************************************************************************
 .\"
-.\" $Id: curs_variables.3x,v 1.5 2013/06/22 20:39:35 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
@@ -99,7 +104,7 @@ This variable holds the number of milliseconds to wait after reading an
 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.
@@ -110,9 +115,18 @@ when converting a tab character to spaces as it adds the tab to a window
 .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,
@@ -125,12 +139,49 @@ or \fBnewterm\fR(3X).
 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).