Announcing ncurses 5.0

The ncurses (new curses) library is a free software emulation of curses in System V Release 4.0, and more. It uses terminfo format, supports pads and color and multiple highlights and forms characters and function-key mapping, and has all the other SYSV-curses enhancements over BSD curses.

In mid-June 1995, the maintainer of 4.4BSD curses declared that he considered 4.4BSD curses obsolete, and is encouraging the keepers of Unix releases such as BSD/OS, freeBSD and netBSD to switch over to ncurses.

The ncurses code was developed under GNU/Linux. It should port easily to any ANSI/POSIX-conforming UNIX. It has even been ported to OS/2 Warp!

The distribution includes the library and support utilities, including a terminfo compiler tic(1), a decompiler infocmp(1), clear(1), tput(1), tset(1), and a termcap conversion tool captoinfo(1). Full manual pages are provided for the library and tools.

The ncurses distribution is available via anonymous FTP at the GNU distribution site ftp://ftp.gnu.org/pub/gnu/ncurses. It is also available at ftp://ftp.clark.net/pub/dickey/ncurses.

Release Notes

We decided to release ncurses as a new whole number release (5.0) because it incorporates several interface changes, including some that would invalidate existing shared libraries. These are the highlights from the change-log since ncurses 4.2 release.

Interface changes:

• The principal source of changes to the interface comes from the release of X/Open Curses in 1997. Earlier versions of ncurses (4.0 and before) were based on a draft version of the specification. The release version adds parameters to some functions to support the evolving internationalization of curses. These summarize the impact:
  • modified several prototypes to correspond with 1997 version of X/Open Curses (affects ABI since developers have used attr_get).
  • corrected prototypes for slk_* functions, using chtype rather than attr_t.
  • the slk_attr_{set,off,on} functions need an additional void* parameter according to XSI.
  • correct macros for wattr_set, wattr_get, separate wattrset macro from these to preserve behavior that allows attributes to be combined with color pair numbers.
  • reviewed/updated curses.h, term.h against X/Open Curses Issue 4 Version 2. This includes making some parameters NCURSES_CONST rather than const, e.g., in termcap.h.
  • reviewed/corrected macros in curses.h as per XSI document.
  • add set_a_attributes and set_pglen_inch to terminfo structure, as per XSI and Solaris 2.5.
• The newest version of the X/Open Curses is implemented on Solaris and other vendor's systems. It adds new features to the terminfo descriptions:
  • implement tparm %l format.
  • implement tparm printf-style width and precision for %s, %d, %x, %o as per XSI.
• We made additional changes to reduce impact by future interface changes:
  • rename key_names[] array to _nc_key_names since it is not part of the curses interface.
  • move macro winch to a function, to hide details of struct ldat
• modify configure script to embed ABI in shared libraries for HP-UX 10.x (detailed request by Tim Mooney).
• modify configuration of shared libraries on Digital Unix so that versioning is embedded in the library, rather than implied by links (patch by Tim Mooney).

New features:

• enable sigwinch handler by default.
• turn on hashmap scrolling code by default
• improved support for termcap applications
  • modify tput to accept termcap names as an alternative to terminfo names.
  • provide support for termcap PC variable by copying it from terminfo data and using it as the padding character in tputs.
  • provide support for termcap ospeed variable by copying it from the internal cur_term member, and using ospeed as the baudrate reference for the delay_output and tputs functions.
  • change name-comparisons in lib_termcap to compare no more than 2 characters.
  • add configure option --enable-tcap-names, which essentially allows users to define new capabilities as in termcap.
• add mouse support to ncurses menus.
• add mouse and dll support for OS/2 EMX
• modify terminfo parsing to accept octal and hexadecimal constants
• add configure option --enable-no-padding, to allow environment variable $NCURSES_NO_PADDING to eliminate non-mandatory padding, thereby making terminal emulators (e.g., for vt100) a little more efficient.
• modify lib_color.c to eliminate dependency on orig_colors and orig_pair, since SVr4 curses does not require these either, but uses them when they are available.
• add -f option to infocmp and tic, which formats the terminfo if/then/else/endif so that they are readable (with newlines and tabs).
• modify tic to compile into %'char' form in preference to %{number}, since that is a little more efficient.

Major bug fixes:

• modify lib_tstp.c to block SIGTTOU when handling SIGTSTP, fixes a problem where ncurses applications which were run via a shell script would hang when given a ^Z. Also, check if the terminal's process group is consistent, i.e., a shell has not taken ownership of it, before deciding to save the current terminal settings in the SIGTSTP handler.
• suppress sc/rc capabilities from terminal description if they appear in smcup/rmcup. This affects only scrolling optimization, to fix a problem reported by several people with xterm's alternate screen, though the problem is more general.
• modify relative_move and tputs to avoid an interaction with the BSD-style padding. The relative_move function could produce a string to replace on the screen which began with a numeric character, which was then interpreted by tputs as padding.
• modify setupterm so that cancelled strings are treated the same as absent strings, cancelled and absent booleans false (does not affect tic, infocmp).
• modify lib_vidattr.c to allow for terminal types (e.g., xterm-color) which may reset all attributes in the 'op' capability, so that colors are set before turning on bold and other attributes, but still after turning attributes off.
• use 'access()' to check if ncurses library should be permitted to open or modify files with fopen/open/link/unlink/remove calls, in case the calling application is running in setuid mode.
• correction to doupdate, for case where terminal does not support insert/delete character. The logic did not check that there was a difference in alignment of changes to old/new screens before repainting the whole non-blank portion of the line. Modified to fall through into logic that reduces by the portion which does not differ.

Features of Ncurses

The ncurses package is fully compatible with SVr4 (System V Release 4) curses:

• All 257 of the SVr4 calls have been implemented (and are documented).
• Full support for SVr4 curses features including keyboard mapping, color, forms-drawing with ACS characters, and automatic recognition of keypad and function keys.
• An emulation of the SVr4 panels library, supporting a stack of windows with backing store, is included.
• An emulation of the SVr4 menus library, supporting a uniform but flexible interface for menu programming, is included.
• An emulation of the SVr4 form library, supporting data collection through on-screen forms, is included.
• Binary terminfo entries generated by the ncurses tic(1) implementation are bit-for-bit-compatible with the entry format SVr4 curses uses.
• The utilities have options to allow you to filter terminfo entries for use with less capable curses/terminfo versions such as the HP/UX and AIX ports.

The ncurses package also has many useful extensions over SVr4:

• The API is 8-bit clean and base-level conformant with the X/OPEN curses specification, XSI curses (that is, it implements all BASE level features, but not all EXTENDED features). Most EXTENDED-level features not directly concerned with wide-character support are implemented, including many function calls not supported under SVr4 curses (but portability of all calls is documented so you can use the SVr4 subset only).
• Unlike SVr3 curses, ncurses can write to the rightmost-bottommost corner of the screen if your terminal has an insert-character capability.
• Ada95 and C++ bindings.
• Support for mouse event reporting with X Window xterm and OS/2 console windows.
• Extended mouse support via Alessandro Rubini's gpm package.
• The function wresize() allows you to resize windows, preserving their data.
• The function use_default_colors() allows you to use the terminal's default colors for the default color pair, achieving the effect of transparent colors.
• The functions keyok() and define_key() allow you to better control the use of function keys, e.g., disabling the ncurses KEY_MOUSE, or by defining more than one control sequence to map to a given key code.
• Support for 16-color terminals, such as aixterm and XFree86 xterm.
• Better cursor-movement optimization. The package now features a cursor-local-movement computation more efficient than either BSD's or System V's.
• Super hardware scrolling support. The screen-update code incorporates a novel, simple, and cheap algorithm that enables it to make optimal use of hardware scrolling, line-insertion, and line-deletion for screen-line movements. This algorithm is more powerful than the 4.4BSD curses quickch() routine.
• Real support for terminals with the magic-cookie glitch. The screen-update code will refrain from drawing a highlight if the magic- cookie unattributed spaces required just before the beginning and after the end would step on a non-space character. It will automatically shift highlight boundaries when doing so would make it possible to draw the highlight without changing the visual appearance of the screen.
• It is possible to generate the library with a list of pre-loaded fallback entries linked to it so that it can serve those terminal types even when no terminfo tree or termcap file is accessible (this may be useful for support of screen-oriented programs that must run in single-user mode).
• The tic(1)/captoinfo utility provided with ncurses has the ability to translate many termcaps from the XENIX, IBM and AT&T extension sets.
• A BSD-like tset(1) utility is provided.
• The ncurses library and utilities will automatically read terminfo entries from $HOME/.terminfo if it exists, and compile to that directory if it exists and the user has no write access to the system directory. This feature makes it easier for users to have personal terminfo entries without giving up access to the system terminfo directory.
• You may specify a path of directories to search for compiled descriptions with the environment variable TERMINFO_DIRS (this generalizes the feature provided by TERMINFO under stock System V.)
• In terminfo source files, use capabilities may refer not just to other entries in the same source file (as in System V) but also to compiled entries in either the system terminfo directory or the user's $HOME/.terminfo directory.
• A script (capconvert) is provided to help BSD users transition from termcap to terminfo. It gathers the information in a TERMCAP environment variable and/or a ~/.termcap local entries file and converts it to an equivalent local terminfo tree under $HOME/.terminfo.
• Automatic fallback to the /etc/termcap file can be compiled in when it is not possible to build a terminfo tree. This feature is neither fast nor cheap, you don't want to use it unless you have to, but it's there.
• The table-of-entries utility toe makes it easy for users to see exactly what terminal types are available on the system.
• The library meets the XSI requirement that every macro entry point have a corresponding function which may be linked (and will be prototype-checked) if the macro definition is disabled with #undef.
• An HTML "Introduction to Programming with NCURSES" document provides a narrative introduction to the curses programming interface.

State of the Package

Numerous bugs present in earlier versions have been fixed; the library is far more reliable than it used to be. Bounds checking in many `dangerous' entry points has been improved. The code is now type-safe according to gcc -Wall. The library has been checked for malloc leaks and arena corruption by the Purify memory-allocation tester.

The ncurses code has been tested with a wide variety of applications including (versions starting with those noted):

cdk

Curses Development Kit Curses Development Kit ftp://ftp.clark.net/pub/dickey/cdk.

ded

directory-editor ftp://ftp.clark.net/pub/dickey/ded.

dialog

the underlying application used in Slackware's setup, and the basis for similar applications on GNU/Linux.

lynx

the character-screen WWW browser

Midnight Commander 4.1

file manager

mutt

mail utility

ncftp

file-transfer utility

nvi

New vi versions 1.50 are able to use ncurses versions 1.9.7 and later.

tin

newsreader, supporting color, MIME ftp://ftp.akk.uni-karlsruhe.de/pub/news/clients/tin-unoff.

taper

tape archive utility

vh-1.6

Volks-Hypertext browser for the Jargon File

as well as some that use ncurses for the terminfo support alone:

minicom

terminal emulator

vile

vi-like-emacs ftp://ftp.clark.net/pub/dickey/vile.

The ncurses distribution includes a selection of test programs (including a few games).

Who's Who and What's What

The original developers of ncurses are Zeyd Ben-Halim and Eric S. Raymond. Ongoing work is being done by Thomas Dickey and Jürgen Pfeifer. Thomas Dickey acts as the maintainer for the Free Software Foundation, which holds the copyright on ncurses. Contact the current maintainers at bug-ncurses@gnu.org.

To join the ncurses mailing list, please write email to bug-ncurses-request@gnu.org containing the line:

             subscribe <name>@<host.domain>

This list is open to anyone interested in helping with the development and testing of this package.

Beta versions of ncurses and patches to the current release are made available at ftp://ftp.clark.net/pub/dickey/ncurses.

Future Plans

• Extended-level XPG4 conformance, with internationalization support.
• Ports to more systems, including DOS and Windows.

We need people to help with these projects. If you are interested in working on them, please join the ncurses list.

Other Related Resources

The distribution includes and uses a version of the terminfo-format terminal description file maintained by Eric Raymond. http://earthspace.net/~esr/terminfo.

You can find lots of information on terminal-related topics not covered in the terminfo file at Richard Shuford's archive.