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## Introduction
Notcurses abandons the X/Open Curses API bundled as part of the Single UNIX
Specification. For some necessary background, consult Thomas E. Dickey's
superb and authoritative [NCURSES FAQ](https://invisible-island.net/ncurses/ncurses.faq.html#xterm_16MegaColors).
As such, Notcurses is not a drop-in Curses replacement.
Wherever possible, Notcurses makes use of the Terminfo library shipped with
NCURSES, benefiting greatly from its portability and thoroughness.
Notcurses opens up advanced functionality for the interactive user on
workstations, phones, laptops, and tablets, possibly at the expense of e.g.
some industrial and retail terminals. Fundamentally, Curses assumes the minimum
and allows you (with effort) to step up, whereas Notcurses assumes the maximum
and steps down (by itself) when necessary. The latter approach probably breaks
on some older hardware, but the former approach results in new software looking
like old hardware.
Why use this non-standard library?
* Thread safety, and efficient use in parallel programs, has been a design
consideration from the beginning.
* A more orderly surface than that codified by X/Open: Exported identifiers are
prefixed to avoid common namespace collisions. Where reasonable,
`static inline` header-only code is used. This facilitates compiler
optimizations, and reduces loader time. Notcurses can be built without its
multimedia functionality, requiring a significantly lesser set of dependencies.
* All APIs natively support the Universal Character Set (Unicode). The `nccell`
API is based around Unicode's [Extended Grapheme Cluster](https://unicode.org/reports/tr29/) concept.
* Visual features including images, fonts, video, high-contrast text, sprites,
and transparent regions. All APIs natively support 24-bit color, quantized
down as necessary for the terminal.
* Portable support for bitmapped graphics, whether using Sixel, Kitty, the iTerm2
protocol, or even the Linux framebuffer console.
* Support for unambiguous [keyboard protocols](https://sw.kovidgoyal.net/kitty/keyboard-protocol/).
* "TUI mode" facilitates high-performance, non-scrolling, full-screen
applications. "CLI mode" supports scrolling output for shell utilities,
but with the full power of Notcurses.
* It's Apache2-licensed in its entirety, as opposed to the
[drama in several acts](https://invisible-island.net/ncurses/ncurses-license.html)
that is the NCURSES license (the latter is [summarized](https://invisible-island.net/ncurses/ncurses-license.html#issues_freer)
as "a restatement of MIT-X11").
Much of the above can be had with NCURSES, but they're not what NCURSES was
*designed* for. On the other hand, if you're targeting industrial or critical
applications, or wish to benefit from time-tested reliability and
portability, you should by all means use that fine library.
## Requirements
Minimum versions generally indicate the oldest version I've tested with; it
may well be possible to use still older versions. Let me know of any successes!
* (build) CMake 3.14.0+ and a C11 compiler
* (OPTIONAL) (OpenImageIO, testing, C++ bindings): A C++17 compiler
* (build+runtime) From [NCURSES](https://invisible-island.net/ncurses/announce.html): terminfo 6.1+
* (build+runtime) GNU [libunistring](https://www.gnu.org/software/libunistring/) 0.9.10+
* (OPTIONAL) (build+runtime) [libgpm](https://www.nico.schottelius.org/software/gpm/) 1.20+
* (OPTIONAL) (build+runtime) From QR-Code-generator: [libqrcodegen](https://github.com/nayuki/QR-Code-generator) 1.5.0+
* (OPTIONAL) (build+runtime) From [FFmpeg](https://www.ffmpeg.org/): libswscale 5.0+, libavformat 57.0+, libavutil 56.0+
* (OPTIONAL) (build+runtime) [OpenImageIO](https://github.com/OpenImageIO/oiio) 2.15.0+, requires C++
* (OPTIONAL) (testing) [Doctest](https://github.com/onqtam/doctest) 2.3.5+
* (OPTIONAL) (documentation) [pandoc](https://pandoc.org/index.html) 1.19.2+
* (OPTIONAL) (python bindings): Python 3.7+, [CFFI](https://pypi.org/project/cffi/) 1.13.2+, [pypandoc](https://pypi.org/project/pypandoc/) 1.5+
* (OPTIONAL) (rust bindings): rust 1.47.0+, [bindgen](https://crates.io/crates/bindgen) 0.55.1+, pkg-config 0.3.18+, cty 0.2.1+
* (runtime) Linux 5.3+, FreeBSD 11+, DragonFly BSD 5.9+, Windows Vista+, or macOS 11.4+
[Here's more information](INSTALL.md) on building and installation.
### Wrappers
If you wish to use a language other than C to work with Notcurses, numerous
wrappers are available. Several are included in this repository, while
others are external.
| Language | Lead(s) | Repository |
| -------- | ----------------------------- | ---------- |
| Ada | Jeremy Grosser | [JeremyGrosser/notcursesada](https://github.com/JeremyGrosser/notcursesada) |
| C++ | Marek Habersack, nick black | internal |
| Python | nick black | internal |
| Python | igo95862 | internal |
| Rust | José Luis Cruz | [dankamongmen/libnotcurses-sys](https://github.com/dankamongmen/libnotcurses-sys) |
| Zig | Jakub Dundalek | [dundalek/notcurses-zig-example](https://github.com/dundalek/notcurses-zig-example) |
## Included tools
Eight binaries are installed as part of Notcurses:
* `ncls`: an `ls` that displays multimedia in the terminal
* `ncneofetch`: a [neofetch](https://github.com/dylanaraps/neofetch) ripoff
* `ncplayer`: renders visual media (images/videos)
* `nctetris`: a tetris clone
* `notcurses-demo`: some demonstration code
* `notcurses-info`: detect and print terminal capabilities/diagnostics
* `notcurses-input`: decode and print keypresses
* `notcurses-tester`: unit testing
To run `notcurses-demo` from a checkout, provide the `data` directory via
the `-p` argument. Demos requiring data files will otherwise abort. The base
delay used in `notcurses-demo` can be changed with `-d`, accepting a
floating-point multiplier. Values less than 1 will speed up the demo, while
values greater than 1 will slow it down.
`notcurses-tester` likewise requires that `data`, populated with the necessary
data files, be specified with `-p`. It can be run by itself, or via `make test`.
## Documentation
With `-DUSE_PANDOC=on` (the default), a full set of man pages and XHTML
will be built from `doc/man`. The following Markdown documentation is included
directly:
* Per-release [News](NEWS.md) for packagers, developers, and users.
* The `TERM` environment variable and [various terminal emulators](TERMINALS.md).
* Notes on [contributing](doc/CONTRIBUTING.md) and [hacking](doc/HACKING.md).
* There's a semi-complete [reference guide](USAGE.md).
* A list of [other TUI libraries](doc/OTHERS.md).
* Abbreviated [history](doc/HISTORY.md) and thanks.
* [Differences from](doc/CURSES.md) Curses and adapting Curses programs.
If you (understandably) want to avoid the large Pandoc stack, but still enjoy
manual page goodness, I publish a tarball with generated man/XHTML along with
each release. Download it, and install the contents as you deem fit.
## Environment notes
* If your `TERM` variable is wrong, or that terminfo definition is out-of-date,
you're going to have a very bad time. Use *only* `TERM` values appropriate
for your terminal. If this variable is undefined, or Notcurses can't load the
specified Terminfo entry, it will refuse to start, and you will
[not be going to space today](https://xkcd.com/1133/).
* Notcurses queries the terminal on startup, enabling some advanced features
based on the determined terminal (and even version). Basic capabilities,
however, are taken from Terminfo. So if you have, say, Kitty, but
`TERM=vt100`, you're going to be able to draw RGBA bitmap graphics (despite
such things being but a dream for a VT100), but *unable* to use the alternate
screen (despite it being supported by every Kitty version). So `TERM` and an
up-to-date Terminfo database remain important.
* Ensure your `LANG` environment variable is set to a UTF8-encoded locale, and
that this locale has been generated. This usually means
`"[language]_[Countrycode].UTF-8"`, i.e. `en_US.UTF-8`. The first part
(`en_US`) ought exist as a directory or symlink in `/usr/share/locales`.
This usually requires editing `/etc/locale.gen` and running `locale-gen`.
On Debian systems, this can be accomplished with `dpkg-reconfigure locales`,
and enabling the desired locale. The default locale is stored somewhere like
`/etc/default/locale`.
* If your terminal has an option about default interpretation of "ambiguous-width
characters" (this is actually a technical term from Unicode), ensure it is
set to **Wide**, not narrow (if that doesn't work, ensure it is set to
**Narrow**, heh).
* If your terminal supports 3x8bit RGB color via `setaf` and `setbf` (most
modern terminals), but exports neither the `RGB` nor `Tc` terminfo capability,
you can export the `COLORTERM` environment variable as `truecolor` or `24bit`.
Note that some terminals accept a 24-bit specification, but map it down to
fewer colors. RGB is unconditionally enabled whenever
[most modern terminals](TERMINALS.md) are identified.
### Fonts
Glyph width, and indeed whether a glyph can be displayed at all, is dependent
in part on the font configuration. Ideally, your font configuration has a
glyph for every Unicode EGC, and each glyph's width matches up with the C
library's `wcswidth()` result for the EGC. If this is not the case, you'll
likely get blanks or � (U+FFFD, REPLACEMENT CHARACTER) for missing characters,
and subsequent characters on the line may be misplaced.
It is worth knowing that several terminals draw the block characters directly,
rather than loading them from a font. This is generally desirable. Quadrants
and sextants are not the place to demonstrate your design virtuosity. To
inspect your environment's rendering of drawing characters, run
`notcurses-info`. The desired output ought look something like this:
intro.TERM value is correct for your terminal.
intro does a palette fade, which is prone to breaking under
incorrect TERM values.
If you're not using xterm, your TERM should not be
xterm!
NCOPTION_NO_ALTERNATE_SCREEN,
NCOPTION_NO_CLEAR_BITMAPS, and NCOPTION_PRESERVE_CURSOR,
and call `ncplane_set_scrolling()` on the standard plane. You still must
explicitly render.
-DUSE_MULTIMEDIA=none.
notcurses_core_init() or
ncdirect_core_init() in place of notcurses_init()/
ncdirect_init(), and link with -lnotcurses-core.
Your application will likely start a few milliseconds faster;
more importantly, it will link against minimal Notcurses installations.
screen.screen doesn't support RGB colors (at least as of 4.08.00);
if you have COLORTERM defined, you'll have a bad time.
If you have a screen that was compiled with
--enable-colors256, try exporting
TERM=screen-256color as opposed to TERM=screen.
mosh.NCKEY_RESIZE until I press
some other key.SIGWINCH in some thread,
and that thread is receiving the signal instead of the thread which called
notcurses_getc_blocking(). As a result, the poll()
is not interrupted. Call pthread_sigmask() before spawning any
threads.
NotCurses
destructor is run when I return from main()?NotCurses is scoped to main()).
ncplane_move_yx(), move it underneath an opaque plane with
ncplane_move_below(), or move it off-pile with
ncplane_reparent().
ncplane_box_yx()? Do you hate
orthogonality, you dullard?ncplane_box() and friends
already have far too many arguments, you monster.
graphics/qr-code-generator.cmake -DCMAKE_REQUIRED_INCLUDES=/usr/local/include.
This is passed by bsd.port.mk.
LANG environment variable is underdefined or incorrectly
defined, or the necessary locale is not present on your machine (it is also
possible that you explicitly supplied NCOPTION_INHIBIT_SETLOCALE,
but never called setlocale(3), in which case don't do that).
ncplane when using a
nccell. Why doesn't the latter hold a pointer to the former?
nccell needs to
remain as small as possible, and you almost always have the ncplane
handy if you've got a reference to a valid nccell anyway.
notcurses-demo, but my table numbers don't match
the Notcurses banner numbers, you charlatan.notcurses-demo renders several frames beyond the actual demos.
notcurses_stop()/ncdirect_stop()
on all exit paths, including fatal signals (note that, by default, Notcurses
installs handlers for most fatal signals to do exactly this).
ncreader.
pkg-config --static --libs notcurses
(or --libs notcurses-core) to discover them.
COLORTERM=24bit
everywhere?SendEnv COLORTERM to .ssh/config, and
AcceptEnv COLORTERM to sshd_config on the remote
server. Yes, this will probably require root on the remote server.
Don't blame me, man; I didn't do it.
ncvisual from RGBA memory using
ncvisual_from_rgba().
NCSTYLE_REVERSE?ncchannels_reverse()
to correctly invert fore- and background colors.
ncsubproc widget.
notcurses_refresh() after notcurses_init()
returns successfully.