# Announcing ncurses 6.0

## 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 is better known today as 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 OSX.
- 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 via anonymous FTP at the GNU distribution site

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

It is also available at

> ftp://invisible-island.net/ncurses/ .

## Release Notes

These notes are for ncurses 6.0, released August 8, 2015.

This release is designed to be source-compatible with ncurses 5.0 through 5.9; providing a new application binary interface (ABI). Although the source can still be configured to support the ncurses 5 ABI, the intent of the release is to provide extensions which are generally useful, but binary-incompatible with ncurses 5:

- Extend the `cchar_t` structure to allow more than 16 colors to be encoded.

- Modify the encoding of mouse state to make room for a 5th mouse button. That allows one to use ncurses with a wheel mouse with xterm or similar X terminal emulators.

There are, of course, numerous other improvements, including

- fixes made based on the Clang and Coverity static analyzers.

- memory leak fixes using Valgrind

The release notes mention some bug-fixes, but are focused on new features and improvements to existing features log since ncurses 5.9 release.

While the intent of the release is to provide a new stable ABI, there are other development activities which are summarized below.

- The original release plan, e.g., for "5.10" was to improve the MinGW port. Ultimately that was completed (wide-character support, mouse, etc), but was deferred to focus on termcap support and performance issues. Also, pinpointing the problems with `Console2` took a while.

- A review of termcap compatibility in 2011 led to several minor fixes in the library and improvements to utilities. To do this properly, a review of the various extent termcap implementations was needed.

  The termcap library checker (tctest) (not part of ncurses) was one result. A followup review of performance using ncurses-examples in 2014 led to additional improvements.

- Output buffering provided a further, but worthwhile distraction. A bug report in 2012 regarding the use of signal handlers in ncurses) pointed out a problem with the use of unsafe functions for handling `SIGTSTP`. Other signals could be addressed with workarounds; repairing `SIGTSTP` required a different approach. The solution required changing internal behavior of the library: how it handles output buffering.

  Now ncurses buffers its own output, independently of the standard output. A few applications relied upon the library's direct reuse of the standard output buffering; however that is unspecified behavior and has never been a recommended practice. Identifying these applications as well as refining the change to permit low-level applications to work consistently took time.

- Since the introduction of the experimental support for 256 colors early in 2005 (released in ncurses 5.5), there has been increased user interest. Almost all packagers continue providing the ncurses ABI 5 which cannot support 256 colors.

- Symbol versioning, or the lack of it in ncurses, is the main reason why packagers would be reluctant to add a new ncurses ABI.

  This release provides the new ABI along with script-generated lists of versioned symbols which can be used for both ABI 5 and 6 (with distinct names to keep the two separate). This took time to development, as reported in Symbol versioning in ncurses.

### Library improvements

### Output buffering

X/Open curses provides more than one initialization function:

- initscr (the simplest) accepts no parameters.
- newterm accepts parameters for the stream input and output
- setupterm (the low-level function) accepts a parameter for the file descriptor of the output.

They are documented in X/Open as if `initscr` calls `newterm` using `stdout` for output stream, and in turn `newterm` calls `setupterm` using `fileno(stdout)` for the file descriptor. As long as an implementation acts as if it does this, it conforms. In practice, implementations do what is implied. This creates a problem: the low-level `setupterm` function's file descriptor is unbuffered, while `newterm` implies buffered output. X/Open Curses says that all output is done through the file descriptor, and does not say how the output stream is actually used.

Initially, ncurses used the file descriptor (obtained from the output stream passed to `newterm`) for changing the terminal modes, and relied upon the output parameter of `newterm` for buffered output. Later (to avoid using unsafe buffered I/O in signal handlers), ncurses was modified to use the file descriptor (unbuffered output) when cleaning up on receipt of a signal. Otherwise (when not handling a signal), it continued to use the buffered output.

That approach worked reasonably well and as a side effect, using the same buffered output as an application might use for `printf` meant that no flushing was needed when switching between normal- and screen-modes.

There were a couple of problems:

- to get good performance, curses (not only ncurses, but SVr4 curses in general) set an output buffer using `setbuf` or similar function. There is no standard (or portable) way to turn that output buffer off, and revert to line-buffering. The `NCURSES_NO_SETBUF` environment variable did make it optional.

- to handle `SIGTSTP` (the “stop” signal), ncurses relied upon unsafe functions. That is, due to the complexity of the feature, it relied upon reusing existing functions which should not have been called via the signal handler.

Conveniently, solving the second problem (by making ncurses do its own output buffering) also fixed the first one. But there were special cases to resolve: low-level functions such as mvcur, putp, vidattr explicitly use the standard output. Those functions were reused internally, and required modification to distinguish whether they were used by the high-level or low-level interfaces.

Finally, there may still be a few programs which should be modified to improve their portability, e.g., adding an

>     fflush(stdout);

when switching from “shell” mode to “program” (curses) mode. Those are fairly rare because most programmers have learned not to mix `printf` and `printw`.

### Symbol versioning

This release introduces symbol-versioning to ncurses because without it, the change of ABI would be less successful. A lengthy discussion will be presented in Symbol versioning in ncurses. These notes summarize what has changed, and what can be done with the new release.

Symbol-versioning allows the developers of a library to mark each public symbol (both data and functions) with an identifier denoting the library name and the version for which it was built. By doing this, users of the library have a way to help ensure that applications do not accidentally load an incompatible library. In addition, private symbols can be hidden entirely.

This release provides sample files for the four principal configurations of ncurses libraries: `ncurses`, `ncursesw`, `ncursest` and `ncursestw`. Each sample is given in two forms:

> “`.map`”
>   These list all public symbols, together with version names.
> “`.sym`”
>   These list all public symbols, without version names.

The sample files are generated by scripts which take into account a few special cases such as tack to omit many of the ncurses private symbols (beginning with “`_nc_`”). Here are counts of globals versus locals:

> Config | Symbols | Globals | Locals | "_nc_"
> --- | --- | --- | --- | ---
> ncurses | 976 | 796 | 180 | 332
> ncursesw | 1089 | 905 | 184 | 343
> ncursest | 979 | 804 | 175 | 358
> ncursestw | 1098 | 914 | 184 | 372

Although only four sample configurations are presented, each is formed by merging symbols from several combinations of configure-script options, taking into account advice from downstream packagers. Because they are formed by merging, the sample files may list a symbol which is not in a given package. That is expected. The samples have been tested and are working with systems (such as Fedora, FreeBSD and Debian) which fully support this feature. There are other systems which do not support the feature, and a few (such as Solaris) which provide incomplete support.

The version-naming convention used allows these sample files to build distinct libraries for ABI 5 and 6. Version names consist of

- configuration name, e.g., “`NCURSESW`” for the wide-character libraries

- ABI version (if not 5)

- library name for two special cases which have the same interface across configurations: “`TINFO`” and “`TIC`”

- release version

- patch date (for the release version)

For example, running `nm -D` on the libraries in the ncurses6 test package shows these symbol-versions:

>     0000000000000000 A NCURSES6_TIC_5.0.19991023
>     0000000000000000 A NCURSES6_TIC_5.1.20000708
>     0000000000000000 A NCURSES6_TIC_5.5.20051010
>     0000000000000000 A NCURSES6_TIC_5.7.20081102
>     0000000000000000 A NCURSES6_TIC_5.9.20150530
>     0000000000000000 A NCURSES6_TINFO_5.0.19991023
>     0000000000000000 A NCURSES6_TINFO_5.1.20000708
>     0000000000000000 A NCURSES6_TINFO_5.2.20001021
>     0000000000000000 A NCURSES6_TINFO_5.3.20021019
>     0000000000000000 A NCURSES6_TINFO_5.4.20040208
>     0000000000000000 A NCURSES6_TINFO_5.5.20051010
>     0000000000000000 A NCURSES6_TINFO_5.6.20061217
>     0000000000000000 A NCURSES6_TINFO_5.7.20081102
>     0000000000000000 A NCURSES6_TINFO_5.8.20110226
>     0000000000000000 A NCURSES6_TINFO_5.9.20150530
>     0000000000000000 A NCURSESW6_5.1.20000708
>     0000000000000000 A NCURSESW6_5.3.20021019
>     0000000000000000 A NCURSESW6_5.4.20040208
>     0000000000000000 A NCURSESW6_5.5.20051010
>     0000000000000000 A NCURSESW6_5.6.20061217
>     0000000000000000 A NCURSESW6_5.7.20081102
>     0000000000000000 A NCURSESW6_5.8.20110226
>     0000000000000000 A NCURSESW6_5.9.20150530

As a special case, this release (which makes the final change for ABI 5) is marked with release version 5.9 and patch date 20150530.

### Miscellaneous

The new release has several improvements for performance and building. For instance:

- several files in ncurses- and progs-directories were modified to allow `const` data used in internal tables to be put by the linker into the readonly text segment.

- various improvements were made to building the Ada95 binding, both in simplifying the generated files as well as improving the way it uses `gnatmake`

There are also new features in the libraries:

- added use_tioctl function

- added wgetdelay to retrieve _delay member of WINDOW if it happens to be opaque, e.g., in the pthread configuration.

- added A_ITALIC extension.

- added form library extension O_DYNAMIC_JUSTIFY option which can be used to override the different treatment of justification for static versus dynamic fields .

- rewrote putwin and getwin, making an extended version which is capable of reading screen-dumps between the wide/normal ncurses configurations. These are text files, except for a magic code at the beginning:

  >     0       string          \210\210        Screen-dump (ncurses)

- several changes to mouse support include:

  - added decoder for xterm SGR 1006 mouse mode.
  - added experimental support for “`%u`” format to terminfo.
  - improved behavior of wheel-mice for xterm protocol: noting that there are only button-presses for buttons “4” and “5”, so there is no need to wait to combine events into double-clicks .

There are a few new configure options dealing with library customization:

- add “`--enable-ext-putwin`” configure option to turn on the extended putwin/getwin. By default, this is enabled for ABI 6 and disabled with ABI 5.

- add “`--enable-string-hacks`” option to control whether strlcat and strlcpy may be used. Because ncurses already does the requisite buffer-limit checks, this feature is mainly of interest to quiet compiler-warnings on a few systems.

- add configure option “`--with-tparm-arg`” to allow tparm's parameters to be something more likely to be the same size as a pointer, e.g., `intptr_t` (again, the default is set for ABI 6).

### Program improvements

#### Utilities

Most of the termcap-related changes based on development of tctest (termcap library checker) are implemented in the tic and infocmp programs rather than affecting the library. As noted in the discussion of `tctest`, ncurses's ability to translate between terminfo and termcap formats has been improved at different times, but subject to feedback from "real" termcap users. There are very few of those. Nowadays, virtually all termcap users are using ncurses (or NetBSD, with its own terminfo library) and their programs are actually using terminfo rather than termcap data.

Still, there are a few. A comment about the translation of the ASCII `NUL` character prompted a review:

- Both terminfo and termcap store string capabilities as `NUL`-terminated strings.

- In terminfo, a `\0` in a terminal description is stored as `\200`.

- There are no (known) terminals which would behave differently when sent `\0` or `\200`.

- When translating to terminfo format (or displaying a printable version of an entry using infocmp), ncurses shows `\200` as `\0`.

- It has done this since 1998 (quoting from the NEWS file):

  >     980103
  >     ...
  >             + modify _nc_tic_expand() to generate \0 rather than \200.
  >     ...
  >             + correct translation of terminfo "^@", to \200, like \0.

- However, the `_nc_tic_expand` function (which optionally produces terminfo or termcap format) did not address this special case for termcap. Even the later 4.4BSD cgetstr interprets a `\0` literally, ending that string (rather than using the terminfo improvement).

As a result of the review, several improvements were made to ncurses translation to/from termcap format — and improving the checks made in tic for consistency of entries. Most of these are not of general interest, except for two new command-line options for tic and infocmp:

- the “`-0`” option generates termcap/terminfo source on a single line.

- the “`-K`” option provides stricter BSD-compatibility for termcap output.

Other user-visible improvements and new features include:

- added “`-D`” option to tic and infocmp, to show the database locations that it could use.

- added “`-s`” option to toe, to sort its output.

- extended “`-c`” and “`-n`” options of infocmp to allow comparing more than two entries.

- modified toe's report when “`-a`” and “`-s`” options are combined, to add a column showing which entries belong to a given database.

- modified the clear program to take into account the “`E3`” extended capability to clear the terminal's scrollback buffer.

#### Examples

Along with the library and utilities, many improvements were made to the ncurses-examples. Some were made to allow building (and comparison-testing) against NetBSD curses and PDCurses. Both lack some of the X/Open Curses features, necessitating customization. But this activity was useful because it showed some remaining performance issues (which have been resolved in this release).

These changes were made to verify compatibility or compare performance of ncurses:

- made workarounds for compiling test-programs with NetBSD curses, though it lacks some common functions such as use_env.

- added dots_termcap test-program

- added dots_curses test-program, for comparison with the low-level examples.

- added test_setupterm test-proram to demonstrate normal/error returns from the setupterm and restartterm functions.

- added “`-d`”, “`-e`” and “`-q`” options to the demo_terminfo and demo_termcap test-programs.

- added “`-y`” option to demo_termcap and test/demo_terminfo test-programs to demonstrate behavior with/without extended capabilities.

- modified demo_termcap and demo_terminfo test-programs to make their options more directly comparable, and add “`-i`” option to specify a terminal description filename to parse for names to lookup.

- rewrote the tests for mvderwin and test for recursive mvwin in the movewindow test-program.

These changes were made to help with the MinGW port:

- added test-screens to the ncurses test-program to show 256-characters at a time, to help with MinGW port.

- modified the view test-program to load UTF-8 when built with MinGW by using regular win32 API because the MinGW functions mblen and mbtowc do not work.

- added “`-s`” option to the view test-program to allow it to start in single-step mode, reducing size of trace files when it is used for debugging MinGW changes.

These changes were made to verify new extensions in ncurses:

- added form_driver_w entrypoint to wide-character forms library, as well as form_driver_w test-program.

- modified ncurses test-program's b/B tests to display lines only for the attributes which a given terminal supports, to make room for an italics test.

- modified ncurses test-program, adding “`-E`” and “`-T`” options to demonstrate use_env versus use_tioctl.

- modified ncurses test-program's c/C tests to cycle through subsets of the total number of colors, to better illustrate 8/16/88/256-colors by providing directly comparable screens.

- modified the ncurses test-program to also show position reports in 'a' test.

These changes were made to make the examples more useful:

- added scripts for building dpkg and rpm test-packages

- modified the hanoi test-program to show the minimum number of moves possible for the given number of tiles.

- modified the knight test-program to show the number of choices possible for each position in automove option, e.g., to allow user to follow Warnsdorff's rule to solve the puzzle.

### Terminal database

This release provides improvements to tic's “`-c`” checking option, which was used for example to

- make `sgr` in several entries agree with other caps.

- correct padding in some entries where earlier versions had miscounted the number of octal digits.

There are several new terminal descriptions:

- mlterm is now aliased to mlterm3
- nsterm is now derived from nsterm-256color
- putty-sco
- teken is FreeBSD's "xterm" console.
- terminator
- terminology
- tmux is derived from screen.
- several screen.XXX entries support the respective variations for 256 colors.
- simpleterm is now 0.5
- vte is aliased to vte-2012
- vt520ansi

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

- `E3`, used in linux, putty and xterm-basic is tested in the clear program to erase a terminal's scrollback.

- `TS` is used in the xterm+sl building block to help deprecate the misuse of `tsl` for xterm's title-string.

- `XT` is used in some terminfo entries to improve usefulness for other applications than screen, which would like to pretend that xterm's title is a status-line.

- `xm` is used in examples xterm-1005 and xterm-1006 to illustrate a way to make mouse handling more general

A few terminals support italics and/or dim capabilities. In particular, screen does not. Documented that, and accommodated the terminals where this feature works with the `A_ITALIC` extension.

- konsole, mlterm3 (italics)
- nsterm (dim)
- screen (dim)
- vte (dim, italics)
- xterm (dim, italics)

### 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, the mechanism for producing HTML versions of the documentation has been improved:

- use an improved version of man2html to generate html manpages.

- regenerated NCURSES-Programming-HOWTO.html to fix some of the broken html emitted by docbook.

### Interesting bug-fixes

- Ada95 binding:

  - modify makefile rules to ensure that the PIC option is not used when building a static library

  - make Ada95 build-fix for big-endian architectures such as sparc. This undoes one of the fixes from 20110319, which added an “`Unused`” member to representation clauses, replacing that with pragmas to suppress warnings about unused bits.

- Color and attributes:

  - parenthesize parameter of `COLOR_PAIR` and `PAIR_NUMBER` in curses.h in case it happens to be a comma-expression.

  - improve 20021221 workaround for broken acs, handling a case where that ACS_xxx character is not in the `acsc` string but there is a known wide-character which can be used.

  - modify init_pair to accept -1's for color value after assume_default_colors has been called.

  - add a check in start_color to limit color-pairs to 256 when extended colors are not supported.

- Resizing the screen:

  - propagate error-returns from wresize, i.e., the internal increase_size and decrease_size functions through resize_term.

  - add check for zero/negative dimensions for `resizeterm` and `resize_term`.

  - modify `resizeterm` to always push a `KEY_RESIZE` onto the fifo, even if screensize is unchanged. Modify library to push a `KEY_RESIZE` if there was a SIGWINCH, even if it does not call `resizeterm`). These changes eliminate the case where a SIGWINCH is received, but ERR is returned from `wgetch` or `wgetnstr` because the screen dimensions did not change.

- Low-level interfaces

  - fix an old bug in the termcap emulation; “`%i`” was ignored in `tparm` because the parameters to be incremented were already on the internal stack.

  - change “`%l`” behavior in tparm to push the string length onto the stack rather than saving the formatted length into the output buffer.

  - modify name-comparison for tgetstr, etc., to accommodate legacy applications as well as to improve compatbility with BSD 4.2 termcap implementations (see note for 980725).

- High-level interfaces

  - modify internal recursion in `wgetch` which handles cooked mode to check if the call to `wgetnstr` returned an error. This can happen when both `nocbreak` and `nodelay` are set, for instance (see note for 960418).

  - add a check in internal function `waddch_nosync` to ensure that tab characters are treated as control characters; some broken locales claim they are printable.

  - modify menu library to ensure that a menu's top-row is adjusted as needed to ensure that the current item is on the screen

  - fix special case where double-width character overwrites a single- width character in the first column.

### Configuration changes

#### Major changes

The ncurses 6.0 configure script makes changes to the default value of several configure options, depending on the `--with-abi-version` option (i.e., whether its value is “5” or “6”):

`--enable-const`

  Feature introduced in 970405 supports the use of `const` where X/Open Curses should have, but did not. NetBSD curses does something similar with `const`.

`--enable-ext-colors`

  Extends the `cchar_t` structure to allow more than 16 colors to be encoded. This applies only to the wide-character (`--enable-widec`) configuration.

`--enable-ext-mouse`

  Modifies the encoding of mouse state to make room for a 5th mouse button. That allows one to use ncurses with a wheel mouse with xterm or similar X terminal emulators.

`--enable-ext-putwin`

  Modifies the file-format written by `putwin` to use printable text rather than binary files, allowing `getwin` to read screen dumps written by differently-configured ncurses libraries. The extended `getwin` can still read binary screen dumps from the same configuration of ncurses. This does not change the ABI (the binary interface seen by calling applications).

`--enable-interop`

  Modifies the `FIELDTYPE` structure used for the form library to make it more generic.

`--enable-lp64`

  Allows an application to define `_LP64` to declare `chtype` and `mmask_t` as simply “`unsigned`” rather than the configured types using the `--with-chtype` and `--with-mmask_t` options.

`--enable-sp-funcs`

  Compile-in support for extended functions which accept a SCREEN pointer, reducing the need for juggling the global SP value with set_term and delscreen.

`--with-chtype=uint32_t`

  Makes `chtype` explicitly a 32-bit unsigned value.

`--with-mmask_t=uint32_t`

  Makes `mmask_t` explicitly a 32-bit unsigned value.

`--with-tparm-arg=intptr_t`

  X/Open Curses declares tparm using `long` for each of the parameters aside from the formatting string, presuming that `long` and `char*` are the same size. This configure option uses `intptr_t` which provides a better guarantee of the sizes.

The configure script no longer checks for antique compilers; `c89` is assumed as a minimum. There are a few features from later revisions which are used when available. The configure script makes checks to turn on useful warnings from clang, gcc and icc. You should be able to build ncurses 6.0 with any of the current (or not so current) C compilers available in 2015.

The configure script, by the way, makes changes which do not work with systems whose `/bin/sh` is non-POSIX. This mainly affects Solaris (the other vendor unix systems have followed the POSIX guidelines for the past twenty years). If you must build on Solaris, its xpg4 binaries suffice, e.g.,

> #!/bin/sh
> WHAT=`hostname|sed -e 's/\..*//'`
> OUT=configure.out
> cat >>$OUT <<EOF/
> ** `date`
> ** node: $WHAT
> ** user: `id`
> ** conf: $*
> EOF/
> SHELL=/bin/sh
> if test -f /usr/xpg4/bin/sh
> then
> CONFIG_SHELL=/usr/xpg4/bin/sh
> export CONFIG_SHELL
> SHELL=$CONFIG_SHELL
> fi
> rm -f config.status config.cache
> TOP=$HOME/$WHAT
> $SHELL ./configure --verbose \
> --disable-echo \
> --disable-overwrite \
> --enable-warnings \
> --with-warnings \
> --prefix=$TOP $* 2>&1 | tee -a $OUT

Other major changes to the configure script include:

- ABI 6 is now the default, intending that the existing ABI 5 should build as before using the “`--with-abi-version=5`” option.

- added `--with-extra-suffix` option to help with installing nonconflicting ncurses6 packages, e.g., avoiding header- and library-conflicts.

  NOTE: as a side-effect, this renames

  > `adacurses-config` to `adacurses5-config` and
  > `adacursesw-config` to `adacursesw5-config`

- the configure script looks for gnatgcc if the Ada95 binding is built, in preference to the default gcc/cc. The script also ensures that the Ada95 binding is built with the level of optimization as the C libraries.

- the configure script captures define's related to -D_XOPEN_SOURCE from the configure check and adds those to the *-config and *.pc files, to simplify use for the wide-character libraries.

#### Configuration options

There are several new (or extended) configure options:

`--disable-db-install`

  Do not install the terminal database. This is used to omit features for packages, as done with `--without-progs`. The option simplifies building cross-compile support packages.

`--disable-gnat-projects`

  This option is used for regression testing

`--disable-lib-suffixes`

  Suppress the “w”, “t” or “tw” suffixes which normally would be added to the library names for the `--enable-widec` and `--with-pthread` options.

`--with-cxx-shared`

  When `--with-shared` is set, build libncurses++ as a shared library. This implicitly relies upon building with gcc/g++, since other compiler suites may have differences in the way shared libraries are built. libtool by the way has similar limitations.

`--with-hashed-db`

  Extended this configure option to simplify building with different versions of Berkeley database using FreeBSD ports.

`--with-pc-suffix`

  If ".pc" files are installed, optionally add a suffix to the files and corresponding package names to separate unusual configurations. If no option value is given (or if it is "none"), no suffix is added. This option is used in the test package for ncurses6.

`--with-xterm-kbs`

  Configure xterm's terminfo entries to use either BS (`^H`, i.e., ASCII backspace) or DEL (`^?`, or 127).

### Portability

#### MinGW

Most of the portability-related work since ncurses 5.9 extended and improved the MinGW port introduced in ncurses 5.8.

The MinGW port can be readily cross-compiled:

- modified configure script to allow creating dll's for MinGW when cross-compiling.

- enforced Windows-style path-separator if cross-compiling,

- added scripts for test-builds of cross-compiled packages for ncurses6 to MinGW.

- added pc-files to the MinGW cross-compiling test-packages.

- added script for building test-packages of binaries cross-compiled to MinGW using NSIS.

- added `nc_mingw.h` to installed headers for MinGW port; this is needed for cross-compiling ncurses-examples.

- added test-packages for cross-compiling ncurses-examples using the MinGW test-packages.

The MinGW-specific Windows driver accounts for several changes:

- wide-character display is made usable by replacing MinGW's non-working `wcrtomb` and `wctomb` functions.

- implemented some display features: beep, flash, curs_set.

- the driver handles repainting on endwin/refresh combination.

- modified treatment of `TERM` variable for MinGW port to allow explicit use of the Windows console driver by checking if `$TERM` is set to “`#win32console`” or an abbreviation of that.

- the Windows driver also matches the special `TERM` value “unknown”

- the driver now returns characters for special keys, (like `ansi.sys` does), when keypad mode is off, rather than returning nothing at all.

- the driver checks a new environment variable NCURSES_CONSOLE2 to optionally work around a deficiency in `Console2` (and its descendent `ConsoleZ`) which hang when an application creates a console buffer.

Finally, there are other improvements:

- MinGW is one of the configurations where ncurses installs by default into /usr

- configuration for cross-compiling uses AC_CHECK_TOOLS in preference to AC_PATH_PROGS when searching for ncurses*-config, e.g., in Ada95/configure and test/configure.

- extend Windows support to work with MSYS2;

  - this works with a scenario where there is an ANSI-escape handler such as `ansicon` running in the console window.

  - wrap `isatty` calls with a macro, provide a corresponding set of support routines to address differences between MinGW and MSYS2.

- ensure `WINVER` is defined in makefiles rather than using headers.

- add check for the `gnatprep` “`-T`” option.

- work around a bug introduced by gcc 4.8.1 in MinGW which breaks "trace" feature.

- add a driver-name method to each of the drivers.

#### Other ports

These changes affect certain platforms (ports):

- the configure script knows how to build shared libraries with DragonFlyBSD and Interix.

- support for AIX shared libraries is improved, tested with AIX 5.3, 6.1 and 7.1 with both gcc 4.2.4 and cc:

  - the shared-library suffix for AIX 5 and 6 is now ".so"

  - the `-brtl` option is used with AIX 5-7; it is needed to link with the shared libraries.

- the configure `--enable-pc-files` option takes into account the `PKG_CONFIG_PATH` variable.

- the configure option `--with-pkg-config-libdir` provides control over the actual directory into which pc-files are installed.

- the build scripts add explicit -ltinfo, etc., to the generated ".pc" file when `ld` option “`--as-needed`” is used, or when ncurses and tinfo are installed without using rpath.

- the configure script disallows conflicting options “`--with-termlib`” and “`--enable-term-driver`”.

- the check for missing c++ compiler to work when no error is reported, and no variables set is improved (see note for 20021206).

- the misc/gen_edit.sh script selects a "linux" entry which works with the current kernel rather than assuming it is always "linux3.0"

- the test/configure script makes it simpler to override names of curses-related libraries, to help with linking with pdcurses in MinGW environment.

- the configure-script/ifdef's allow the BSD OLD_TTY feature to be suppressed if the type of `ospeed` is configured using the option `--with-ospeed` to not be a `short`. By default, it is a `short` for termcap-compatibility.

- the MKlib_gen.sh script works around a recent change in gcc 5 (released mid-2015) which essentially emits multiple `#line` statements for the same position in a file.

- the configure script works with Minix3.2 (see note on portability)

- OS/2 redux:

  - the configure script supports OS/2 kLIBC.

  - the `--with-lib-prefix` option allows configuring for old/new flavors of OS/2 EMX.

- improved configure-script checks for `_XOPEN_SOURCE`:

  - the definition works starting with Solaris 10.

  - the definition is suppressed for IRIX64, since its header files have a conflict versus `_SGI_SOURCE`.

## 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:

> cdk

>   Curses Development Kit

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

> ded

>   directory-editor

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

> dialog

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

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

> lynx

>   the text WWW browser

>   http://lynx.isc.org/

> Midnight Commander

>   file manager

>   http://www.midnight-commander.org/

> mutt

>   mail utility

>   http://www.mutt.org/

> ncftp

>   file-transfer utility

>   http://www.ncftp.com/

> nvi

>   New vi uses ncurses.

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

> tin

>   newsreader, supporting color, MIME

>   http://www.tin.org/

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

> minicom

>   terminal emulator for serial modem connections

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

> mosh

>   a replacement for `ssh`.

>   https://mosh.mit.edu/

> tack

>   terminfo action checker

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

> tmux

>   terminal multiplexor

>   http://tmux.github.io/

> vile

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

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

and finally, those which use only the termcap interface:

> emacs

>   text editor

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

> screen

>   terminal multiplexor

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

> vim

>   text editor

>   http://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 Dickey. Thomas Dickey also 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://invisible-island.net/ncurses/ .

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:

- man2html
- ncurses licensing
- Symbol versioning in ncurses
- The MinGW port of ncurses
- tack – terminfo action checker
- tar versus portability
- 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, and 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 .