textwrap

Version 0.15.2 (2022-10-24)

This release is identical to 0.15.0 and is only there to give people a way to install crates which depend on the yanked 0.15.1 release. See https://github.com/mgeisler/textwrap/issues/484 for details.

Version 0.14.2 (2021-06-27)

The 0.14.1 release included more changes than intended and has been yanked. The change intended for 0.14.1 is now included in 0.14.2.

This is a major release which rewrites the core logic, adds many new features, and fixes a couple of bugs. Most programs which use textwrap stays the same, incompatibilities and upgrade notes are given below.

Clone the repository and run the following to explore the new features in an interactive demo (Linux only):

$ cargo run --example interactive --all-features

Bug Fixes

Rewritten core wrapping algorithm

• #221: Reformulate wrapping in terms of words with whitespace and penalties.

The core wrapping algorithm has been completely rewritten. This fixed bugs and simplified the code, while also making it possible to use textwrap outside the context of the terminal.

As part of this, trailing whitespace is now discarded consistently from wrapped lines. Before we would inconsistently remove whitespace at the end of wrapped lines, except for the last. Leading whitespace is still preserved.

New Features

Optimal-fit wrapping

• #234: Introduce wrapping using an optimal-fit algorithm.

This release adds support for new wrapping algorithm which finds a globally optimal set of line breaks, taking certain penalties into account. As an example, the old algorithm would produce

"To be, or"
"not to be:"
"that is"
"the"
"question"

Notice how the fourth line with “the” is very short. The new algorithm shortens the previous lines slightly to produce fewer short lines:

"To be,"
"or not to"
"be: that"
"is the"
"question"

Use the new textwrap::core::WrapAlgorithm enum to select between the new and old algorithm. By default, the new algorithm is used.

The optimal-fit algorithm is inspired by the line breaking algorithm used in TeX, described in the 1981 article Breaking Paragraphs into Lines by Knuth and Plass.

In-place wrapping

• #226: Add a fill_inplace function.

When the text you want to fill is already a temporary String, you can now mutate it in-place with fill_inplace:

let mut greeting = format!("Greetings {}, welcome to the game! You have {} lives left.",
                           player.name, player.lives);
fill_inplace(&mut greeting, line_width);

This is faster than calling fill and it will reuse the memory already allocated for the string.

Changed Features

Wrapper is replaced with Options

• #213: Simplify API with only top-level functions.
• #215: Reintroducing the type parameter on Options (previously known as Wrapper).
• #219: Allow using trait objects with fill & wrap.
• #227: Replace WrapOptions with Into<Options>.

The Wrapper struct held the options (line width, indentation, etc) for wrapping text. It was also the entry point for actually wrapping the text via its methods such as wrap, wrap_iter, into_wrap_iter, and fill methods.

The struct has been replaced by a simpler Options struct which only holds options. The Wrapper methods are gone, their job has been taken over by the top-level wrap and fill functions. The signature of these functions have changed from

fn fill(s: &str, width: usize) -> String;

fn wrap(s: &str, width: usize) -> Vec<Cow<'_, str>>;

to the more general

fn fill<'a, S, Opt>(text: &str, options: Opt) -> String
where
    S: WordSplitter,
    Opt: Into<Options<'a, S>>;

fn wrap<'a, S, Opt>(text: &str, options: Opt) -> Vec<Cow<'_, str>>
where
    S: WordSplitter,
    Opt: Into<Options<'a, S>>;

The Into<Options<'a, S> bound allows you to pass an usize (which is interpreted as the line width) and a full Options object. This allows the new functions to work like the old, plus you can now fully customize the behavior of the wrapping via Options when needed.

Code that call textwrap::wrap or textwrap::fill can remain unchanged. Code that calls into Wrapper::wrap or Wrapper::fill will need to be update. This is a mechanical change, please see #213 for examples.

Thanks to @CryptJar and @Koxiat for their support in the PRs above!

Removed Features

• The wrap_iter and into_wrap_iter methods are gone. This means that lazy iteration is no longer supported: you always get all wrapped lines back as a Vec. This was done to simplify the code and to support the optimal-fit algorithm.

  The first-fit algorithm could still be implemented in an incremental fashion. Please let us know if this is important to you.

Other Changes

• #206: Change Wrapper.splitter from T: WordSplitter to Box<dyn WordSplitter>.
• #216: Forbid the use of unsafe code.

This is a bugfix release.

• Fixed #176: Mention compile-time wrapping by linking to the [textwrap-macros crate].
• Fixed #193: Wrapping with break_words(false) was broken and would cause extra whitespace to be inserted when words
  were longer than the line width.

The code has been updated to the [Rust 2018 edition][rust-2018] and each new release of textwrap will only support the latest stable version of Rust. Trying to support older Rust versions is a fool's errand: our dependencies keep releasing new patch versions that require newer and newer versions of Rust.

The term_size feature has been replaced by terminal_size. The API is unchanged, it is just the name of the Cargo feature that changed.

The hyphenation feature now only embeds the hyphenation patterns for US-English. This slims down the dependency.

• Fixed #140: Ignore ANSI escape sequences.
• Fixed #158: Unintended wrapping when using external splitter.
• Fixed #177: Update examples to the 2018 edition.

Due to our dependencies bumping their minimum supported version of Rust, the minimum version of Rust we test against is now 1.22.0.

• Merged #141: Fix dedent handling of empty lines and trailing newlines. Thanks @bbqsrc!
• Fixed #151: Release of version with hyphenation 0.7.

Due to our dependencies bumping their minimum supported version of Rust, the minimum version of Rust we test against is now 1.17.0.

• Fixed #99: Word broken even though it would fit on line.
• Fixed #107: Automatic hyphenation is off by one.
• Fixed #122: Take newlines into account when wrapping.
• Fixed #129: Panic on string with em-dash.

The dependency on term_size is now optional, and by default this feature is not enabled. This is a breaking change for users of Wrapper::with_termwidth. Enable the term_size feature to restore the old functionality.

Added a regression test for the case where width is set to usize::MAX, thanks @Fraser999! All public structs now implement Debug, thanks @hcpl!

• Fixed #101: Make term_size an optional dependency.

The Wrapper stuct is now generic over the type of word splitter being used. This means less boxing and a nicer API. The Wrapper::word_splitter method has been removed. This is a breaking API change if you used the method to change the word splitter.

The Wrapper struct has two new methods that will wrap the input text lazily: Wrapper::wrap_iter and Wrapper::into_wrap_iter. Use those if you will be iterating over the wrapped lines one by one.

• Fixed #59: wrap could return an iterator. Thanks @hcpl!
• Fixed #81: Set html_root_url.

Version 0.7.0 changes the return type of Wrapper::wrap from Vec<String> to Vec<Cow<'a, str>>. This means that the output lines borrow data from the input string. This is a breaking API change if you relied on the exact return type of Wrapper::wrap. Callers of the textwrap::fill convenience function will see no breakage.

The above change and other optimizations makes version 0.7.0 roughly 15-30% faster than version 0.6.0.

The squeeze_whitespace option has been removed since it was complicating the above optimization. Let us know if this option is important for you so we can provide a work around.

• Fixed #58: Add a fast_wrap function.
• Fixed #61: Documentation errors.

Version 0.6.0 adds builder methods to Wrapper for easy one-line initialization and configuration:

let wrapper = Wrapper::new(60).break_words(false);

It also add a new NoHyphenation word splitter that will never split words, not even at existing hyphens.

• Fixed #28: Support not squeezing whitespace.

Version 0.5.0 has breaking API changes. However, this only affects code using the hyphenation feature. The feature is now optional, so
you will first need to enable the hyphenation feature as described above. Afterwards, please change your code from

wrapper.corpus = Some(&corpus);

to

wrapper.splitter = Box::new(corpus);

Other changes include optimizations, so version 0.5.0 is roughly 10-15% faster than version 0.4.0.

• Fixed #19: Add support for finding terminal size.
• Fixed #25: Handle words longer than self.width.
• Fixed #26: Support custom indentation.
• Fixed #36: Support building without hyphenation.
• Fixed #39: Respect non-breaking spaces.

Documented complexities and tested these via cargo bench.

• Fixed #13: Immediately add word if it fits.
• Fixed #14: Avoid splitting on initial hyphens.

Added support for automatic hyphenation.

Introduced Wrapper struct. Added support for wrapping on hyphens.

First public release with support for wrapping strings on whitespace.