crates/textwrap/README.md

# Textwrap

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Textwrap is a library for wrapping and indenting text. It is most
often used by command-line programs to format dynamic output nicely so
it looks good in a terminal. You can also use Textwrap to wrap text
set in a proportional font—such as text used to generate PDF files, or
drawn on a [HTML5 canvas using WebAssembly][wasm-demo].

## Usage

To use the textwrap crate, add this to your `Cargo.toml` file:
```toml
[dependencies]
textwrap = "0.16"
```

By default, this enables word wrapping with support for Unicode
strings. Extra features can be enabled with Cargo features—and the
Unicode support can be disabled if needed. This allows you slim down
the library and so you will only pay for the features you actually
use.

Please see the [_Cargo Features_ in the crate
documentation](https://docs.rs/textwrap/#cargo-features) for a full
list of the available features as well as their impact on the size of
your binary.

## Documentation

**[API documentation][api-docs]**

## Getting Started

Word wrapping is easy using the `wrap` and `fill` functions:

```rust
#[cfg(feature = "smawk")] {
let text = "textwrap: an efficient and powerful library for wrapping text.";
assert_eq!(
    textwrap::wrap(text, 28),
    vec![
        "textwrap: an efficient",
        "and powerful library for",
        "wrapping text.",
    ]
);
}
```

Sharp-eyed readers will notice that the first line is 22 columns wide.
So why is the word “and” put in the second line when there is space
for it in the first line?

The explanation is that textwrap does not just wrap text one line at a
time. Instead, it uses an optimal-fit algorithm which looks ahead and
chooses line breaks which minimize the gaps left at ends of lines.
This is controlled with the `smawk` Cargo feature, which is why the
example is wrapped in the `cfg`-block.

Without look-ahead, the first line would be longer and the text would
look like this:

```rust
#[cfg(not(feature = "smawk"))] {
let text = "textwrap: an efficient and powerful library for wrapping text.";
assert_eq!(
    textwrap::wrap(text, 28),
    vec![
        "textwrap: an efficient and",
        "powerful library for",
        "wrapping text.",
    ]
);
}
```

The second line is now shorter and the text is more ragged. The kind
of wrapping can be configured via `Options::wrap_algorithm`.

If you enable the `hyphenation` Cargo feature, you get support for
automatic hyphenation for [about 70 languages][patterns] via
high-quality TeX hyphenation patterns.

Your program must load the hyphenation pattern and configure
`Options::word_splitter` to use it:

```rust
#[cfg(feature = "hyphenation")] {
use hyphenation::{Language, Load, Standard};
use textwrap::{fill, Options, WordSplitter};

let dictionary = Standard::from_embedded(Language::EnglishUS).unwrap();
let options = textwrap::Options::new(28).word_splitter(WordSplitter::Hyphenation(dictionary));
let text = "textwrap: an efficient and powerful library for wrapping text.";

assert_eq!(
    textwrap::wrap(text, &options),
    vec![
        "textwrap: an efficient and",
        "powerful library for wrap-",
        "ping text."
    ]
);
}
```

The US-English hyphenation patterns are embedded when you enable the
`hyphenation` feature. They are licensed under a [permissive
license][en-us license] and take up about 88 KB in your binary. If you
need hyphenation for other languages, you need to download a
[precompiled `.bincode` file][bincode] and load it yourself. Please
see the [`hyphenation` documentation] for details.

## Wrapping Strings at Compile Time

If your strings are known at compile time, please take a look at the
procedural macros from the [`textwrap-macros` crate].

## Examples

The library comes with [a
collection](https://github.com/mgeisler/textwrap/tree/master/examples)
of small example programs that shows various features.

If you want to see Textwrap in action right away, then take a look at
[`examples/wasm/`], which shows how to wrap sans-serif, serif, and
monospace text. It uses WebAssembly and is automatically deployed to
https://mgeisler.github.io/textwrap/.

For the command-line examples, you’re invited to clone the repository
and try them out for yourself! Of special note is
[`examples/interactive.rs`]. This is a demo program which demonstrates
most of the available features: you can enter text and adjust the
width at which it is wrapped interactively. You can also adjust the
`Options` used to see the effect of different `WordSplitter`s and wrap
algorithms.

Run the demo with

```sh
$ cargo run --example interactive
```

The demo needs a Linux terminal to function.

## Release History

Please see the [CHANGELOG file] for details on the changes made in
each release.

## License

Textwrap can be distributed according to the [MIT license][mit].
Contributions will be accepted under the same license.

[crates-io]: https://crates.io/crates/textwrap
[build-status]: https://github.com/mgeisler/textwrap/actions?query=workflow%3Abuild+branch%3Amaster
[codecov]: https://codecov.io/gh/mgeisler/textwrap
[wasm-demo]: https://mgeisler.github.io/textwrap/
[`textwrap-macros` crate]: https://crates.io/crates/textwrap-macros
[`hyphenation` example]: https://github.com/mgeisler/textwrap/blob/master/examples/hyphenation.rs
[`termwidth` example]: https://github.com/mgeisler/textwrap/blob/master/examples/termwidth.rs
[patterns]: https://github.com/tapeinosyne/hyphenation/tree/master/patterns-tex
[en-us license]: https://github.com/hyphenation/tex-hyphen/blob/master/hyph-utf8/tex/generic/hyph-utf8/patterns/tex/hyph-en-us.tex
[bincode]: https://github.com/tapeinosyne/hyphenation/tree/master/dictionaries
[`hyphenation` documentation]: http://docs.rs/hyphenation
[`examples/wasm/`]: https://github.com/mgeisler/textwrap/tree/master/examples/wasm
[`examples/interactive.rs`]: https://github.com/mgeisler/textwrap/tree/master/examples/interactive.rs
[api-docs]: https://docs.rs/textwrap/
[CHANGELOG file]: https://github.com/mgeisler/textwrap/blob/master/CHANGELOG.md
[mit]: LICENSE