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287 lines
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287 lines
18 KiB
Markdown
# Notcurses: blingful TUIs and character graphics
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* **What it is**: a library facilitating complex TUIs on modern terminal
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emulators, supporting vivid colors, multimedia, threads, and Unicode to the
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maximum degree possible. [Things](https://www.youtube.com/watch?v=cYhZ7myXyyg) can be done with
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Notcurses that simply can't be done with NCURSES.
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* **What it is not**: a source-compatible X/Open Curses implementation, nor a
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replacement for NCURSES on existing systems.
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<p align="center">
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<a href="https://www.youtube.com/watch?v=cYhZ7myXyyg"><img src="https://img.youtube.com/vi/cYhZ7myXyyg/0.jpg" alt="setting the standard (hype video)"/></a>
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</p>
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birthed screaming into this world by [nick black](https://nick-black.com/dankwiki/index.php/Hack_on) (<nickblack@linux.com>).
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* c++ wrappers by [marek habersack](http://twistedcode.net/blog/) (<grendel@twistedcode.net>)
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* rust wrappers by José Luis Cruz (<joseluis@andamira.net>)
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* python wrappers by igo95862 (<igo95862@yandex.ru>)
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for more information, see [dankwiki](https://nick-black.com/dankwiki/index.php/Notcurses)
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and the [man pages](https://notcurses.com/notcurses). in addition, there is
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[Doxygen](https://nick-black.com/notcurses/html/) output. there is a
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[mailing list](https://groups.google.com/forum/#!forum/notcurses) which can be reached
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via notcurses@googlegroups.com. i wrote a coherent
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[guidebook](https://nick-black.com/htp-notcurses.pdf), which is available for
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free download (or [paperback purchase](https://amazon.com/dp/B086PNVNC9)).
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i've not yet added many documented examples, but [src/poc/](https://github.com/dankamongmen/notcurses/tree/master/src/poc)
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and [src/pocpp/](https://github.com/dankamongmen/notcurses/tree/master/src/pocpp)
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contain many small C and C++ programs respectively. `notcurses-demo` covers
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most of the functionality of Notcurses.
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**If you're running Notcurses applications in a Docker, please consult
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"[Environment notes](#environment-notes)" below.**
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[](https://drone.dsscaw.com:4443/dankamongmen/notcurses)
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[](https://pypi.org/project/notcurses)
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[](https://crates.io/crates/libnotcurses-sys)
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[](https://github.com/sponsors/dankamongmen)
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<a href="https://repology.org/project/notcurses/versions">
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<img src="https://repology.org/badge/vertical-allrepos/notcurses.svg" alt="Packaging status" align="right">
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</a>
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## Introduction
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Notcurses abandons the X/Open Curses API bundled as part of the Single UNIX
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Specification. For some necessary background, consult Thomas E. Dickey's
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superb and authoritative [NCURSES FAQ](https://invisible-island.net/ncurses/ncurses.faq.html#xterm_16MegaColors).
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As such, Notcurses is not a drop-in Curses replacement.
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Wherever possible, Notcurses makes use of the Terminfo library shipped with
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NCURSES, benefiting greatly from its portability and thoroughness.
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Notcurses opens up advanced functionality for the interactive user on
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workstations, phones, laptops, and tablets, at the expense of e.g.
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some industrial and retail terminals. Fundamentally, Curses assumes the minimum
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and allows you (with effort) to step up, whereas Notcurses assumes the maximum
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and steps down (by itself) when necessary. The latter approach probably breaks
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on some older hardware, but the former approach results in new software looking
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like old hardware.
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Why use this non-standard library?
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* Thread safety, and efficient use in parallel programs, has been a design
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consideration from the beginning.
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* A svelter design than that codified by X/Open: Exported identifiers are
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prefixed to avoid common namespace collisions. The library object exports a
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minimal set of symbols. Where reasonable, `static inline` header-only code is
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used. This facilitates compiler optimizations, and reduces loader time.
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Notcurses can be built without its multimedia functionality, requiring a
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significantly lesser set of dependencies.
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* All APIs natively support the Universal Character Set (Unicode). The `cell`
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API is based around Unicode's [Extended Grapheme Cluster](https://unicode.org/reports/tr29/) concept.
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* Visual features including images, fonts, video, high-contrast text, sprites,
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and transparent regions. All APIs natively support 24-bit color, quantized
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down as necessary for the terminal.
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* It's Apache2-licensed in its entirety, as opposed to the
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[drama in several acts](https://invisible-island.net/ncurses/ncurses-license.html)
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that is the NCURSES license (the latter is [summarized](https://invisible-island.net/ncurses/ncurses-license.html#issues_freer)
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as "a restatement of MIT-X11").
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Much of the above can be had with NCURSES, but they're not what NCURSES was
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*designed* for. On the other hand, if you're targeting industrial or critical
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applications, or wish to benefit from its time-tested reliability and
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portability, you should by all means use that fine library.
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## Requirements
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Minimum versions generally indicate the oldest version I've tested with; it
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may well be possible to use still older versions. Let me know of any successes!
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* (build) A C11 and a C++17 compiler
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* (build) CMake 3.14.0+
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* (build+runtime) From [NCURSES](https://invisible-island.net/ncurses/announce.html): terminfo 6.1+
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* (build+runtime) GNU [libunistring](https://www.gnu.org/software/libunistring/) 0.9.10+
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* (build+runtime) GNU [Readline](https://www.gnu.org/software/libunistring/) 8.0+
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* (OPTIONAL) (build+runtime) From QR-Code-generator: [libqrcodegen](https://github.com/nayuki/QR-Code-generator) 1.5.0+
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* (OPTIONAL) (build+runtime) From [FFmpeg](https://www.ffmpeg.org/): libswscale 5.0+, libavformat 57.0+, libavutil 56.0+
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* (OPTIONAL) (build+runtime) [OpenImageIO](https://github.com/OpenImageIO/oiio) 2.15.0+
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* (OPTIONAL) (testing) [Doctest](https://github.com/onqtam/doctest) 2.3.5+
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* (OPTIONAL) (documentation) [pandoc](https://pandoc.org/index.html) 1.19.2+
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* (OPTIONAL) (python bindings): Python 3.7+, [CFFI](https://pypi.org/project/cffi/) 1.13.2+, [pypandoc](https://pypi.org/project/pypandoc/) 1.5+
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* (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+
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* (runtime) Linux 5.3+, FreeBSD 11+, or DragonFly BSD 5.9+
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[Here's more information](INSTALL.md) on building and installation.
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## Included tools
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Seven binaries are installed as part of Notcurses:
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* `ncls`: an `ls` that displays multimedia in the terminal
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* `ncneofetch`: a [neofetch](https://github.com/dylanaraps/neofetch) ripoff
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* `ncplayer`: renders visual media (images/videos)
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* `nctetris`: a tetris clone
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* `notcurses-demo`: some demonstration code
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* `notcurses-input`: decode and print keypresses
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* `notcurses-tester`: unit testing
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To run `notcurses-demo` from a checkout, provide the `tests/` directory via
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the `-p` argument. Demos requiring data files will otherwise abort. The base
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delay used in `notcurses-demo` can be changed with `-d`, accepting a
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floating-point multiplier. Values less than 1 will speed up the demo, while
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values greater than 1 will slow it down.
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`notcurses-tester` expects `../tests/` to exist, and be populated with the
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necessary data files. It can be run by itself, or via `make test`.
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## Documentation
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With `-DUSE_PANDOC=on` (the default), a full set of man pages and XHTML
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will be built from `doc/man`. The following Markdown documentation is included
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directly:
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* Per-release [News](NEWS.md) for packagers, developers, and users.
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* The `TERM` environment variable and [various terminal emulators](TERMINALS.md).
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* Notes on [contributing](doc/CONTRIBUTING.md) and [hacking](doc/HACKING.md).
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* There's a semi-complete [reference guide](USAGE.md).
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* A list of [other TUI libraries](doc/OTHERS.md).
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* Abbreviated [history](doc/HISTORY.md) and thanks.
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* [Differences from](doc/CURSES.md) Curses and adapting Curses programs.
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## Environment notes
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* If your `TERM` variable is wrong, or that terminfo definition is out-of-date,
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you're going to have a very bad time. Use *only* `TERM` values appropriate
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for your terminal. If this variable is undefined, or Notcurses can't load the
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specified Terminfo entry, it will refuse to start, and you will
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[not be going to space today](https://xkcd.com/1133/).
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* Ensure your `LANG` environment variable is set to a UTF8-encoded locale, and
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that this locale has been generated. This usually means
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`"[language]_[Countrycode].UTF-8"`, i.e. `en_US.UTF-8`. The first part
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(`en_US`) ought exist as a directory or symlink in `/usr/share/locales`.
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This usually requires editing `/etc/locale.gen` and running `locale-gen`.
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On Debian systems, this can be accomplished with `dpkg-reconfigure locales`,
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and enabling the desired locale. The default locale is stored somewhere like
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`/etc/default/locale`.
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* If your terminal has an option about default interpretation of "ambiguous-width
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characters" (this is actually a technical term from Unicode), ensure it is
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set to **Wide**, not narrow (if that doesn't work, ensure it is set to
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**Narrow**, heh).
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* The unit tests assume dimensions of at least 80x24. They might work in a
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smaller terminal. They might not. Don't file bugs on it.
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### TrueColor detection
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Notcurses primarily loads control sequences from `terminfo(5)`, using the
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database entry specified by the `TERM` environment variable. 24-bit "TrueColor"
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color support (or at least the ability to specify 3 8-bit channels as arguments
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to `setaf` and `setbf`) is indicated by the `rgb` terminfo capability. Many
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terminals with RGB support do not advertise the `rgb` capability. If you
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believe your terminal to support 24-bit TrueColor, this can be indicated by
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exporting the `COLORTERM` environment variable as `truecolor` or `24bit`.
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Note that some terminals accept a 24-bit specification, but map it down to
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fewer colors.
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### Fonts
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Fonts end up being a whole thing, little of which is pleasant. I'll write this
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up someday **FIXME**.
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It is worth knowing that several terminals draw the block characters directly,
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rather than loading them from a font.
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### FAQs
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If things break or seem otherwise lackluster, **please** consult the
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[Environment Notes](#environment_notes) section! You **need** to have a correct
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`TERM` and `LANG` definition, and probably want `COLORTERM`.
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* **Q:** The demo fails in the middle of `intro`. **A:** Check that your `TERM`
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value is correct for your terminal. `intro` does a palette fade, which is prone
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to breaking under incorrect `TERM` values. If you're not using `xterm`, your
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`TERM` should not be `xterm`!
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* **Q:** Can I have Notcurses without this huge multimedia stack? **A:** Yes! Build with `-DUSE_MULTIMEDIA=none`.
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* **Q:** In `xterm`, Alt doesn't work as expected. **A:** Check out the `eightBitInput` resource of `xterm`. Add `XTerm*eightBitInput: false` to your `$HOME/.Xresources`, and run `xrdb -a $HOME/.Xresources`.
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* **Q:** Notcurses looks like absolute crap in `screen`. **A:** `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`.
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* **Q:** Notcurses looks like absolute crap in `mosh`. **A**: Yeah it sure does. I'm not yet sure what's up.
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* **Q:** Why didn't you just use Sixel? **A:** Many terminal emulators don't support Sixel. Sixel doesn't work well with mouse selection. With that said, I do intend to support Sixel soon, as a backend, when available, for certain types of drawing (see [issue #200](https://github.com/dankamongmen/notcurses/issues/200)).
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* **Q:** I'm not seeing `NCKEY_RESIZE` until I press some other key. **A:** You've almost certainly failed to mask `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.
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* **Q:** Using the C++ wrapper, how can I ensure that the `NotCurses` destructor is run when I return from `main()`? **A:** As noted in the [C++ FAQ](https://isocpp.org/wiki/faq/dtors#artificial-block-to-control-lifetimes), wrap it in an artificial scope (this assumes your `NotCurses` is scoped to `main()`).
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* **Q:** How do I hide a plane I want to make visible later? **A:** In order of least to most performant: move it offscreen using `ncplane_move_yx()`, move it underneath an opaque plane with `ncplane_move_below()`, or move it off-pile with `ncplane_reparent()`.
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* **Q:** Why isn't there an `ncplane_box_yx()`? Do you hate orthogonality, you dullard? **A:** `ncplane_box()` and friends already have far too many arguments, you monster.
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* **Q:** Why doesn't Notcurses support 10- or 16-bit color? **A:** Notcurses supports 24 bits of color, spread across three eight-bit channels. You presumably mean 10-bit-per-channel color. Notcurses will support it when a terminal supports it.
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* **Q:** The name is dumb. **A:** That's not a question?
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* **Q:** I'm not finding qrcodegen on BSD, despite having installed `graphics/qr-code-generator`. **A:** Try `cmake -DCMAKE_REQUIRED_INCLUDES=/usr/local/include`. This is passed by `bsd.port.mk`.
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* **Q:** Do you support [musl](https://musl.libc.org/)? **A:** I try to! You'll need at least 1.20.
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* **Q:** I only seem to blit in ASCII, and/or can't emit Unicode beyond ASCII in general. **A:** Your `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).
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* **Q:** I pretty much always need an `ncplane` when using a `cell`. Why doesn't the latter hold a pointer to the former? **A:** Besides the massive redundancy this would entail, `cell` needs to remain as small as possible, and you almost always have the `ncplane` handy if you've got a reference to a valid `cell` anyway.
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* **Q:** I ran `notcurses-demo`, but my table numbers don't match the Notcurses banner numbers, you charlatan. **A:** `notcurses-demo` renders several frames beyond the actual demos.
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* **Q:** When my program exits, I don't have a cursor, or text is invisible, or colors are weird, <i>ad nauseam</i>. **A:** Ensure you're calling `notcurses_stop()`/`ncdirect_stop()` on all exit paths, including fatal signals.
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* **Q:** How can I use Direct Mode in conjunction with libreadline? **A:** Pass `NCDIRECT_OPTION_CBREAK` to `ncdirect_init()`, and ensure you do not pass `NCDIRECT_OPTION_NO_READLINE`. If you'd like, set `rl_readline_name` and `rl_attempted_completion_function` prior to calling `ncdirect_init()`. With that said, consider using a Notcurses `ncreader`.
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* **Q:** Will there ever be Java wrappers? **A:** I should hope not.
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* **Q:** Given that the glyph channel is initialized as transparent for a plane, shouldn't the foreground and background be initialized as transparent, also? **A:** Probably (they are instead initialized to default opaque). This would change some of the most longstanding behavior of Notcurses, though, so it isn't happening.
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* **Q:** Why does my right-to-left text appear left-to-right? **A:** Notcurses doesn't honor the BiDi state machine, and in fact forces left-to-right with BiDi codes. Likewise, ultra-wide glyphs will have interesting effects. ﷽!
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* **Q:** I get linker errors when statically linking. **A:** Are you linking all necessary libraries? Use `pkg-config --static --libs notcurses` to discover them.
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* **Q:** Can I avoid manually exporting `COLORTERM=24bit` everywhere? **A:** Sure. Add `SendEnv COLORTERM` to `.ssh/config`, and `AcceptEnv COLORTERM` to `sshd_config` on the remote server.
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## Useful links
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* [BiDi in Terminal Emulators](https://terminal-wg.pages.freedesktop.org/bidi/)
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* [The Xterm FAQ](https://invisible-island.net/xterm/xterm.faq.html)
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* [XTerm Control Sequences](https://invisible-island.net/xterm/ctlseqs/ctlseqs.pdf)
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* [The NCURSES FAQ](https://invisible-island.net/ncurses/ncurses.faq.html)
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* [ECMA-35 Character Code Structure and Extension Techniques](https://www.ecma-international.org/publications/standards/Ecma-035.htm) (ISO/IEC 2022)
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* [ECMA-43 8-bit Coded Character Set Structure and Rules](https://www.ecma-international.org/publications/standards/Ecma-043.htm)
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* [ECMA-48 Control Functions for Coded Character Sets](https://www.ecma-international.org/publications/standards/Ecma-048.htm) (ISO/IEC 6429)
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* [Unicode 13.1 Full Emoji List](https://unicode.org/emoji/charts/full-emoji-list.html)
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* [Unicode Standard Annex #29 Text Segmentation](http://www.unicode.org/reports/tr29)
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* [Unicode Standard Annex #15 Normalization Forms](https://unicode.org/reports/tr15/)
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* [The TTY demystified](http://www.linusakesson.net/programming/tty/)
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* [Dark Corners of Unicode](https://eev.ee/blog/2015/09/12/dark-corners-of-unicode/)
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* [UTF-8 Decoder Capability and Stress Test](https://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-test.txt)
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* [Emoji: how do you get from U+1F355 to 🍕?](https://meowni.ca/posts/emoji-emoji-emoji/)
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* [Glyph Hell: An introduction to glyphs, as used and defined in the FreeType engine](http://chanae.walon.org/pub/ttf/ttf_glyphs.htm)
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### Useful man pages
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* Linux: [console_codes(4)](http://man7.org/linux/man-pages/man4/console_codes.4.html)
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* Linux: [termios(3)](http://man7.org/linux/man-pages/man3/termios.3.html)
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* Linux: [ioctl_tty(2)](http://man7.org/linux/man-pages/man2/ioctl_tty.2.html)
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* Linux: [ioctl_console(2)](http://man7.org/linux/man-pages/man2/ioctl_console.2.html)
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* Portable: [terminfo(5)](http://man7.org/linux/man-pages/man5/terminfo.5.html)
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* Portable: [user_caps(5)](http://man7.org/linux/man-pages/man5/user_caps.5.html)
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### Grotesque vanity and meaningless metrics
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[](https://starcharts.herokuapp.com/dankamongmen/notcurses)
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> “Our fine arts were developed, their types and uses were established, in times
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very different from the present, by men whose power of action upon things was
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insignificant in comparison with ours. But the amazing growth of our
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techniques, the adaptability and precision they have attained, the ideas and
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habits they are creating, make it a certainty that _profound changes are
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impending in the ancient craft of the Beautiful_.” —Paul Valéry
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