# Announcing ncurses 6.2

## Overview

The ncurses (new curses) library is a free software emulation of curses in System V Release 4.0 (SVr4), 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 SVr4-curses enhancements over BSD curses. SVr4 curses became the basis of X/Open Curses.

In mid-June 1995, the maintainer of 4.4BSD curses declared that he considered 4.4BSD curses obsolete, and encouraged the keepers of unix releases such as BSD/OS, FreeBSD and NetBSD to switch over to ncurses.

Since 1995, ncurses has been ported to many systems:

- It is used in almost every system based on the Linux kernel (aside from some embedded applications).
- It is used as the system curses library on OpenBSD, FreeBSD and MacOS.
- It is used in environments such as Cygwin and MinGW. The first of these was EMX on OS/2 Warp.
- It is used (though usually not as the system curses) on all of the vendor unix systems, e.g., AIX, HP-UX, IRIX64, SCO, Solaris, Tru64.
- It should work readily on any ANSI/POSIX-conforming unix.

The distribution includes the library and support utilities, including

- captoinfo, a termcap conversion tool
- clear, utility for clearing the screen
- infocmp, the terminfo decompiler
- tabs, set tabs on a terminal
- tic, the terminfo compiler
- toe, list (table of) terminfo entries
- tput, utility for retrieving terminal capabilities in shell scripts
- tset, to initialize the terminal

Full manual pages are provided for the library and tools.

The ncurses distribution is available at ncurses' homepage:

> ftp://ftp.invisible-island.net/ncurses/ or
> https://invisible-mirror.net/archives/ncurses/ .

It is also available via anonymous FTP at the GNU distribution site

> ftp://ftp.gnu.org/gnu/ncurses/ .

## Release Notes

These notes are for ncurses 6.2, released February 12, 2020.

This release is designed to be source-compatible with ncurses 5.0 through 6.1; providing extensions to the application binary interface (ABI). Although the source can still be configured to support the ncurses 5 ABI, the reason for the release is to reflect improvements to the ncurses 6 ABI and the supporting utility programs.

There are, of course, numerous other improvements, listed in this announcement.

The most important bug-fixes/improvements dealt with user-defined capabilities in terminal descriptions. The release notes also mention some other bug-fixes, but are focused on new features and improvements to existing features since ncurses 6.1 release.

### Library improvements

#### New features

There are several new features:

- O_EDGE_INSERT_STAY tells the form library to optionally delay cursor movement on a field edge/boundary

- O_INPUT_FIELD extension to form library allows a dynamic field to shrink if the new limit is smaller than the current field size.

- added exit_curses and exit_terminfo to replace internal symbols for leak-checking.

- added curses_trace, to replace trace().

Additionally, to improve performance other changes (and extensions) are provided in this release:

- mouse decoding now handles shift/control/alt logic when decoding xterm's 1006 mode

- ncurses now defines a limit for wgetnstr, wgetn_wstr when length is negative or “too large”.

- reordered loop-limit checks in winsnstr in case the string has no terminating null and only the number of characters is used.

- there is now no buffer-size limit when reading the `$TERMCAP` variable.

- the `$TERMCAP` variable may be interpreted as a fallback to a terminfo entry

- `mvcur` now decides whether to use hard-tabs, using `xt`, `tbc` and `hts` as clues.

- extended colors are improved by modifying an internal call to `vid_puts` to pass extended color pairs e.g., from `tty_update.c` and `lib_mvcur.c`

- the initialization functions now avoid relying upon persistent data for the result from `getenv`

- scrolling is improved:

  - a limit check in `newline_forces_scroll` handles the case where the row is inside scroll-margins, but not at the end.

  - improved loop limits in `_nc_scroll_window` handle a case where the scrolled data is a pad which is taller than the window.

#### Other improvements

These are revised features:

- used “`const`” in some prototypes rather than `NCURSES_CONST` where X/Open Curses was updated to do this, e.g., `wscanw`, `newterm`, the terminfo interface. Also use “`const`” for consistency in the termcap interface, which was withdrawn by X/Open Curses in Issue 5 (2007). As of Issue 7, X/Open Curses still lacks “`const`” for certain return values, e.g., keyname.

- modified `wbkgd` and `wbkgrnd` to improve compatibility with SVr4 curses, changing the way the window rendition is updated when the background character is modified

- improved terminfo write/read by modifying the fourth item of the extended header to denote the number of valid strings in the extended string table (see term(5)).

- modified the initialization checks for mouse so that the `xterm+sm+1006` block will work with terminal descriptions not mentioning xterm.

These were done to limit or ultimately deprecate features:

- deprecated safe-sprintf, since the `vsnprintf` function, which does what was needed, was standardized long ago.

- marked `vwprintw` and `vwscanw` as deprecated; recommend using `vw_printw` and `vw_scanw`, respectively.

- added deprecation warnings for internal functions called by older versions of tack.

- removed unused `_nc_import_termtype2` function.

These are improvements to existing features:

- check parameter of set_escdelay, return ERR if negative.

- check parameter of set_tabsize, return ERR if not greater than zero

- correct a status-check in _nc_read_tic_entry() so that if reading a hex/b64 `$TERMINFO`, and the `$TERM` does not match, fall-through to the compiled-in search list.

- amend check for `repeat_char` to handle a case where setlocale() was called after `initscr`

- move macro for `is_linetouched` inside `NCURSES_NOMACROS` `ifndef`.

- use `_nc_copy_termtype2` rather than direct assignment in setupterm, in case it is called repeatedly using fallback terminfo descriptions

- improve workaround for Solaris wcwidth versus line-drawing characters

- add checks in `repair_subwindows` to keep the current position and scroll-margins inside the resized subwindow.

- correct a buffer-limit in `write_entry.c` for systems that use caseless filenames.

- improved build-time utility report_offsets:

  - add categories, e.g., "w" for wide-character, "t" for threads to make the report more readable. Reorganized the structures reported to make the categories more apparent.

  - add `NCURSES_GLOBALS` and `NCURSES_PRESCREEN` to report to show how similar the different libtinfo configurations are.

- modified some header files to ensure that those include necessary files except for the previously-documented cases

- added some traces in initialization to show whether a fallback entry is used.

- made minor optimization to reduce calls to _nc_reserve_pairs

These are corrections to existing features:

- fix a special case in `PutAttrChar` where a cell is marked as alternate-character set, but the terminal does not actually support the given graphic character. This would happen in an older terminal such as vt52, which lacks most line-drawing capability.

- corrected flag for "seq" method of db 1.8.5 interface, needed by toe on some of the BSDs.

- modify comparison in make_hash.c to correct a special case in collision handling for Caps-hpux11

- add extended_slk_color{,_sp} symbols to the appropriate package/*.{map,sym} files

- modify lib_setup to avoid calling pthread_self() without first verifying that the address is valid, i.e., for weak symbols

- add a couple of broken-linker symbols to the list of versioned symbols to help with link-time optimization versus weak symbols.

### Program improvements

Several improvements were made to the utility programs:

clear
  - improved logic for clearing with the E3 extension, in case the terminal scrolls content onto its saved-lines before actually clearing the display, by clearing the saved-lines after clearing the display
infocmp
  - omit filtering of “`OTxx`” names which are used for obsolete capabilities, when the output is sorted by long-names. This change helps when making a table of the short/long capability names.
tic
  - added check for consistent alternate character set capabilities.
  - added check for paired `indn`/`rin`.
  - added check for terminals with `parm_dch` vs `parm_ich`.
  - added check for the case where `setf`/`setb` are given using different strings, but provide identical results to `setaf`/`setab`.
  - corrected check for `ich1`.
  - changed a too-large terminal entry from a fatal error to a warning.
toe
  - ignores any hex/b64 `$TERMINFO` value in the list of terminfo databases.
tset
  - replace check in reset command for obsolete “`pt`” capability using `tbc` and `hts` capabilities as clues
  - modify reset to allow for tabstops at intervals other than 8.
  - change reset's behavior for margins to simply clear soft-margins if possible, rather than clearing and then setting them according to the terminal's width.
tput
  - add “`x`” to `getopt` string so that “`tput -x clear`” works.

Several changes were made to the generated ncurses*config scripts and the analogous “`.pc`” files to reduce differences between the configurations they report:

- modified the ncurse*-config and pc-files to more closely match for the `-I` and `-l` options.

- filtered out linker-specs from the `--libs` report.

- amended the ncurses*-config and pc-files to take into account the rpath hack which differed between those files.

- modified generated ncurses*config and ncurses.pc, ncursesw.pc, etc., to list helper libraries such as gpm for static linking.

#### Examples

Along with the library and utilities, improvements were made to the ncurses-examples. Most of this activity aimed at improving the test-packages. A few changes are more generally useful, e.g., for the main ncurses test-program, and for analyzing traces using the tracemunch script:

- improve recovery from error when reading command-character in `test/ncurses.c`, showing the relevant error message and not exiting on EINTR.

- improve tracemunch, by keeping track of `TERMINAL*` values, and if tracing was first turned on after initialization, attempt to show distinct screen, window and terminal names anyway.

- modify tracemunch to accept filename parameters in addition to use as a pipe/filter.

- update tracemunch to work with perl 5.26.2, which changed the rules for escaping regular expressions.

- add some checks in tracemunch for undefined variables.

- modify `TurnOn`/`TurnOff` macros (in lib_vidattr.c and lib_vid_attr.c) to avoid expansion of “`CUR`” in trace.

There are other new demo/test programs and reusable examples:

color_content
  Demonstrate the `color_content` and `extended_color_content` functions.
demo_tabs
  A simple demo of tabs in curses.
dump_window
  A portable curses screen-dump, used to compare ncurses screen contents with Solaris.
pair_content
  Demonstrate the `pair_content` and `extended_pair_content` functions.
report_hashing
  Check hash-tables used for terminfo and termcap names.
parse_rgb
  Sample implementation of the ncurses RGB extension from user_caps.5, used in picsmap and savescreen programs.

A variety of improvements were made to existing programs, both new features as well as options added to make the set of programs more consistent.

- add “`-l`” option to test/background, to dump screen contents in a form that lets different curses implementations be compared.

- add “`@`” command to test/ncurses F-test, to allow rapid jump to different character pages.

- added enum, regex examples to test/demo_forms

- amend Scaled256() macro in test/picsmap.c to cover the full range 0..1000

- corrected pathname used in Ada95 sample programs for `explain.txt`, to work with test-packages, and used an awk script to split the resulting pathname when it would be too long for a single line.

- ignore interrupted system-call in test/ncurses's command-line, e.g., if the terminal were resized.

- improved ifdef's for `TABSIZE` variable, to help with AIX/HPUX ports.

### Terminal database

There are several new terminal descriptions:

> `alacritty`, `domterm`, `kitty`, `mintty`, `mintty-direct`, `ms-terminal`, `n7900`, `nsterm-build309`, `nsterm-direct`, `screen5`, `ti703`, `ti707`, `ti703-w`, `ti707-w` `vscode`, `vscode-direct`, `xterm-mono`, `xterm.js`

There are many changes to existing terminal descriptions. Some were updates to several descriptions:

- use `ansi+rep` in a dozen places
- add rs1 to konsole, mlterm
- improve several flash capabilities with trailing mandatory delays
- drop `ich1` from `rxvt-basic`, `Eterm` and `mlterm` to improve compatibility with old non-curses programs
- add/use `xterm+keypad` in `xterm-new`
- use `xterm+sl-twm` for consistency, nine places
- improve xm example in xterm+x11mouse and xterm+sm_1006.

while others affected specific descriptions. These were retested, to take into account changes by their developers:

> `terminator`, `st`

while these are specific fixes based on reviewing documentation, user reports, or warnings from tic:

adds200:
  - fix typo
gnome-256color
  - base entry on "gnome", not "vte", for consistency
interix
  - trim unnecessary setf/setb
linux-16color
  - accommodate Linux console driver incompatibility introduced in early 2018
nsterm-256color:
  - add nsterm-build309 to replace nsterm-256color, assigning the latter as an alias of nsterm, to make mouse work with nsterm-256color
regent40:
  - renumber function-keys to match manual
regent60:
  - add cd (clr_eos)
  - corrected acsc
  - add shifted function-keys
tvi950:
  - added function-key definitions to agree with Televideo 950 manual
  - corrected acsc
  - remove bogus kf0
  - add bel
tvi955:
  - fix typo
vi200:
  - add acsc string, including right/down-arrow
wy50:
  - corrected acsc
wy50 and wy60:
  - add shifted function-keys as kF1 to kF16
xterm+x11hilite:
  - eliminate unused p5 parameter.

A few entries use extensions (user-defined terminal capabilities):

- use `xterm+sm+1006` (aka “SGR 1006 mouse”) for konsole-base and putty
- add `Smol/Rmol` user-defined capability to `tmux` and `vte-2018`
- add `Smulx` user-defined capability to `tmux`, `vte-2018`

### Documentation

As usual, this release

- improves documentation by describing new features,

- attempts to improve the description of features which users have found confusing

- fills in overlooked descriptions of features which were described in the NEWS file but treated sketchily in manual pages.

In addition to providing background information to explain these features and show how they evolved, there are corrections, clarifications, etc.:

- Corrections:

  - correct error-returns listed in manual pages for a few form functions
  - corrected prototypes in several manpages using script to extract those in compilable form.
  - fix typo in term.5, improve explanation of format

- Clarify in manual pages that vwprintw and vwscanw are obsolete.
  They have not been part of X/Open Curses since 2007.

- New/improved history and portability sections:

  - curs_addch.3x gives some background for ACS symbols.
  - curs_getcchar.3x explains a difference between ncurses and X/Open Curses.
  - curs_getstr.3x gives historical/portability background for the length parameter of `wgetnstr`.
  - curs_slk.3x lists a few differences between SVr4 curses and X/Open Curses for soft-keys.
  - curs_terminfo.3x explains that the initial implementation of terminfo in SVr2 was mostly replaced by other developers in SVr3.
  - infocmp.1 explains that the initial version of terminfo had no tool for decompiling descriptions. That came later, with SVr3, with a different developer.
  - tabs.1 tells more than you wanted to know about the tool.
  - tic.1 explains that the initial version of terminfo had a rudimentary tool (based on termcap) for compiling entries. The tool used with Unix was developed by others for SVr3.
  - toe.1 explains the origin of this tool.

- Improvements for user_caps.5:

  - mention `meml`, `memu` and `box1`
  - expanded description of `XM`
  - add a clarification regarding the `RGB` capability.
  - mention user_caps.5 in the tic and infocmp manual pages.

- Other improvements:

  - curs_add_wch.3x adds note about Unicode terminology for the line-drawing characters.
  - curs_color.3x improves discussion of error returns and extensions.
  - curs_mouse.3x explains how the `kmous` and `XM` capabilities are used for xterm-mouse input.
  - curs_refresh.3x improves documentation regarding the virtual and physical screens.
  - curs_util.3x mentions a difference between SVr4 and X/Open Curses for `unctrl.h`
  - curs_variables.3x improves description of the init_tabs capability and `TABSIZE` variable.
  - ncurses.3x improves documentation regarding feature-test macros in curses.h
  - resizeterm.3x about top-level windows which touch the screen's borders.
  - tput.1 clarifies how tput determines the terminal size.

There are no new manual pages (all of the manual page updates are to existing pages).

Some of the improvements are more subtle, relating to the way the information is presented. For instance, the generated terminfo.5 file uses a different table layout, allowing it to use space on wide terminals more effectively.

### Interesting bug-fixes

While there were many bugs fixed during development of ncurses 6.2, only a few (the reason for this release) were both important and interesting. Most of the bug-fixes were for local issues which did not affect compatibility across releases. Since those are detailed in the NEWS file no elaboration is needed here.

The interesting bugs were in tic/infocmp's handling of user-defined capabilities. These were not recent bugs. Initially it was a simple problem:

- The user-defined capabilities can be any type (boolean, number or string), but once given a type all uses of the name must conform to that type—unless some special support for a particular multi-typed name is built into ncurses.

- One of simpleterm's contributors copied some definitions for using tmux's user-defined capabilities in late in 2016.

  >     diff --git a/st.info b/st.info
  >     @@ -185,7 +185,10 @@ st| simpleterm,
  >       tsl=\E]0;,
  >       xenl,
  >       vpa=\E[%i%p1%dd,
  >     -
  >     +# Tmux unofficial extensions, see TERMINFO EXTENSIONS in tmux(1)
  >     + Se,
  >     + Ss,
  >     + Tc,

  >      st-256color| simpleterm with 256 colors,
  >       use=st,

- Later, in (referring to a version from mid-2017), a user asked to have it updated in ncurses.

- However, it had an error from the change in late 2016. The terminal description made what tmux expected to be string actually a boolean.

  Over the years, there were problems with each of simpleterm's terminal descriptions. I repaired those, and usually dealt with the problem.

- The difference in this case was that when compiling the terminal database, tic may have in memory the definitions for more than one terminal description (so that it can resolve “`use=`” clauses). Seeing two different types for the same name, in certain situations it would incorrectly merge the symbol tables for the two terminal descriptions.

- On simpleterm's side, their bug was finally fixed in late 2019, three years after the bug was created.

For ncurses, the elapsed time to fix this bug was less than three years. Someone reported a problem with the terminal description a few weeks after releasing ncurses 6.1 (in tmux #1264), and the terminal description was updated that week (ncurses patch 20180224):

>     20180224
>             + modify _nc_resolve_uses2() to detect incompatible types when merging
>               a "use=" clause of extended capabilities.  The problem was seen in a
>               defective terminfo integrated from simpleterm sources in 20171111,
>               compounded by repair in 20180121.
>             + correct Ss/Ms interchange in st-0.7 entry (tmux #1264) -TD

The larger part of that change added a check to prevent a simple merge of terminal descriptions where the same user-defined name was used with different types. But it raised some questions:

- Was there a reliable way to manage terminal descriptions which used the same extended name in different ways?

- Should ncurses provide a registry of well-known extended names, with their types?

Since the correction to `terminfo.src` could have been readily adopted by packagers, there was nothing more to be done from ncurses' standpoint on that part. But improving ncurses to prevent issues like that is the reason for making a release.

Nothing more (constructive) was mentioned with regard to simpleterm. But a few problems were found in the handling of user-defined capabilities:

- Forward-references to user-defined capabilities in a “`use=`” clause did not allocate new data for each use. In tic, successive compilation of terminal entries could add user-defined capabilities to the wrong terminal entry.

  This was not noticed before, since xterm's terminal descriptions were the main users of the feature, and almost all of the uses of the building-blocks which contained user-defined capabilities were backward-references.

- There is one (documented) case where ncurses 6.1 supports a user-defined capability that could be any type (i.e., “RGB”). The check added in February 2018 to guard against mismatches did not handle all of the combinations needed.

Both of these issues dated from the original implementation of user-defined capabilities. Fixing them does not change the terminal database, but a older tic without the fixes will not be able to handle terminfo sources which rely upon those fixes. Starting in June 2019, the download link for the terminfo source file was capped at that date. The development sources have an up-to-date copy of the file, for people with a legitimate need for it.

The “`-c`” (check) option of tic is not very useful if it cannot offer advice on parameters needed for user-defined capabilities. The various Caps files were reorganized to reduce redundancy, and in the common portion (Caps-ncurses), a registry of user-defined capabilities is provided for use by tic. While users can still define their own custom capabilities, tic will not offer any advice when their parameters do not match.

In ncurses 6.2, tic makes a special check to allow any type for RGB, but its being able to do this relies upon fixes made in the ncurses library in mid-2019.

### Configuration changes

#### Major changes

There are no major changes. Several new options were added to ease integration of packages with systems using different versions of GNAT and ncurses. Also, improvements were made to configure checks.

#### Configuration options

There are a few new/modified configure options:

`--with-config-suffix`

  helps work around a filename conflict with Debian packages versus test-packages.

`--with-ada-libname`

  allows one to rename the “AdaCurses” library (at least one packager prefers a lowercase name).

`--with-fallbacks`

  now ensures there is a value, and adds the fallback information to top-level Makefile summary.

`--with-pcre2`

  check for pcre-posix library to help with MinGW port.

`--with-tic-path` and
`--with-infocmp-path`

  help work around problems building fallback source using pre-6.0 tic/infocmp.

`--with-versioned-syms`

  option value can now be a relative pathname.

### Portability

Many of the portability changes are implemented via the configure script:

- ignore `$TERMINFO` as a default value in configure script if it came from the `infocmp` `-Q` option.

- distinguish gcc from icc and clang when the `--enable-warnings` option is not used, to avoid unnecessary warnings about unrecognized inline options

- consistently prepend new libraries as they are found during configuration, rather than relying upon the linker to resolve order dependencies of libraries.

- modified configure scripts to reduce relinking/ranlib during library install :

  - use “`install -p`” when available, to avoid need for ranlib of static libraries.
  - scripts which use “`--disable-relink`;” add a 1-second sleep to work around tools which use whole-second timestamps, e.g., in `utime` rather than the actual file system resolution.

- add configure check for `getenv` to work around implementation shown in Emscripten which overwrites the previous return value on each call.

  Use that to optionally suppress `START_TRACE` macro, whose call to `getenv` may not work properly

- change target configure level for `_XOPEN_SOURCE` to 600 to address use of `vsscanf` and `setenv`.

- reduce use of `_GNU_SOURCE` for current glibc where `_DEFAULT_SOURCE` combines with `_XOPEN_SOURCE`

  Allow for Cygwin's newlib when checking for the _DEFAULT_SOURCE symbol.

  MidnightBSD is now checked for the `_XOPEN_SOURCE`-related definitions.

- If the check for `va_copy` or `__va_copy` fails,

  - configure now tries copying the pointers for `va_list`, or as an array.
  - alternatively, it checks for `__builtin_va_copy`(), which could be used with AIX `xlc` in c89 mode.

- several changes to support a port to Ultrix 3.1:

  - check if "b" binary feature of fopen works
  - check for missing feature of locale.h
  - add fallback for strstr() in test-programs
  - add fallback for STDOUT_FILENO in test-programs

- The test/configure script (used for ncurses-examples) is improved:

  - work around non-ncurses termcap.h file, e.g., in Slackware.
  - check for `TABSIZE` variable.
  - checks for the X11/Intrinsic.h header, accommodate recent MacOS changes which largely emptied `/usr/include`.

Here are some of the other portability fixes:

- added dummy "check" rule in top-level and test-Makefile to simplify building test-packages for ArchLinux.

- dropped library-dependency on psapi for MinGW port, since win_driver.c defines `PSAPI_VERSION` to 2, making it use `GetProcessImageFileName` from kernel32.dll

- made build-fixes for configuration using --program-suffix with Ada95, noticed with MacOS but applicable to other platforms without libpanelw, etc.

- modified ncurses/Makefile.in to fix a case where Debian/testing changes to the ld --as-needed configuration broke ncurses-examples test packages.

- used `_WIN32`/`_WIN64` in preference to `__MINGW32__`/`__MINGW64__` symbols to simplify building with Microsoft Visual C++, since the former are defined in both compiler configurations.

## Features of ncurses

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

- All of the SVr4 calls have been implemented (and are documented).

- ncurses supports all of the for SVr4 curses features including keyboard mapping, color, forms-drawing with ACS characters, and automatic recognition of keypad and function keys.

- ncurses provides these SVr4 add-on libraries (not part of X/Open Curses):

  - the panels library, supporting a stack of windows with backing store.

  - the menus library, supporting a uniform but flexible interface for menu programming.

  - the form library, supporting data collection through on-screen forms.

- ncurses's terminal database is fully compatible with that used by SVr4 curses.

  - ncurses supports user-defined capabilities which it can see, but which are hidden from SVr4 curses applications using the same terminal database.

  - It can be optionally configured to match the format used in related systems such as AIX and Tru64.

  - Alternatively, ncurses can be configured to use hashed databases rather than the directory of files used by SVr4 curses.

- The ncurses 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, and most EXTENDED features). It includes 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 FreeBSD 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 256-color terminals, such as modern xterm.

- Support for 16-color terminals, such as aixterm and modern 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/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 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.

- 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`.

- Extensive documentation is provided (see the Additional Reading section of the ncurses FAQ for online documentation).

## Applications using ncurses

The ncurses distribution includes a selection of test programs (including a few games). These are available separately as ncurses-examples

The ncurses library has been tested with a wide variety of applications including:

> aptitude

>   FrontEnd to Apt, the debian package manager

>   https://wiki.debian.org/Aptitude

> cdk

>   Curses Development Kit

>   https://invisible-island.net/cdk/

> ded

>   directory-editor

>   https://invisible-island.net/ded/

> dialog

>   the underlying application used in Slackware's setup, and the basis for similar install/configure applications on many systems.

>   https://invisible-island.net/dialog/

> lynx

>   the text WWW browser

>   https://lynx.invisible-island.net/

> mutt

>   mail utility

>   http://www.mutt.org/

> ncftp

>   file-transfer utility

>   https://www.ncftp.com/

> nvi

>   New vi uses ncurses.

>   https://sites.google.com/a/bostic.com/keithbostic/vi

> ranger

>   A console file manager with VI key bindings in Python.

>   https://ranger.github.io/

> tin

>   newsreader, supporting color, MIME

>   http://www.tin.org/

> vifm

>   File manager with vi like keybindings

>   https://vifm.info/

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

> minicom

>   terminal emulator for serial modem connections

>   https://alioth.debian.org/projects/minicom/

> mosh

>   a replacement for `ssh`.

>   https://mosh.mit.edu/

> tack

>   terminfo action checker

>   https://invisible-island.net/ncurses/tack.html

> tmux

>   terminal multiplexor

>   https://github.com/tmux/tmux/wiki

> vile

>   vi-like-emacs may be built to use the terminfo, termcap or curses interfaces.

>   https://invisible-island.net/vile/

and finally, those which use only the termcap interface:

> emacs

>   text editor

>   https://www.gnu.org/software/emacs/

> less

>   The most commonly used pager (a program that displays text files).

>   http://www.greenwoodsoftware.com/less/

> screen

>   terminal multiplexor

>   https://www.gnu.org/software/screen/

> vim

>   text editor

>   https://www.vim.org/

## Development activities

Zeyd Ben-Halim started ncurses from a previous package pcurses, written by Pavel Curtis. Eric S. Raymond continued development. Jürgen Pfeifer wrote most of the form and menu libraries.

Ongoing development work is done by Thomas E. Dickey. Thomas E. Dickey has acted as the maintainer for the Free Software Foundation, which holds a copyright on ncurses for releases 4.2 through 6.1. Following the release of ncurses 6.1, effective as of release 6.2, copyright for ncurses reverted to Thomas E. Dickey (see the ncurses FAQ for additional information).

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 are made available at

> ftp://ftp.invisible-island.net/ncurses/current/ and
> https://invisible-mirror.net/archives/ncurses/current/ .

Patches to the current release are made available at

> ftp://ftp.invisible-island.net/ncurses/6.1/ and
> https://invisible-mirror.net/archives/ncurses/6.1/ .

There is an archive of the mailing list here:

> http://lists.gnu.org/archive/html/bug-ncurses (also https)

## Related resources

The release notes make scattered references to these pages, which may be interesting by themselves:

- ncurses licensing
- Symbol versioning in ncurses
- Comments on ncurses versus slang (S-Lang)
- tack – terminfo action checker
- tctest – termcap library checker
- Terminal Database

## Other resources

The distribution provides a newer version of the terminfo-format terminal description file once maintained by Eric Raymond . Unlike the older version, the termcap and terminfo data are provided in the same file, which also provides several user-definable extensions beyond the X/Open specification.

You can find lots of information on terminal-related topics not covered in the terminfo file at Richard Shuford's archive . The collection of computer manuals at bitsavers.org has also been useful.