Document width rules

.github/workflows/rust.yml

@@ -1,4 +1,4 @@
-name: Rust
+name: build
 
 on:
   push:

Cargo.toml

@@ -9,8 +9,13 @@ authors = [
 
 homepage = "https://github.com/unicode-rs/unicode-width"
 repository = "https://github.com/unicode-rs/unicode-width"
-documentation = "https://unicode-rs.github.io/unicode-width"
-license = "MIT/Apache-2.0"
+license = "MIT OR Apache-2.0"
+categories = [
+    "command-line-interface",
+    "internationalization",
+    "no-std::no-alloc",
+    "text-processing",
+]
 keywords = ["text", "width", "unicode"]
 readme = "README.md"
 description = """

README.md

@@ -1,17 +1,17 @@
-# unicode-width
+# `unicode-width`
 
-Determine displayed width of `char` and `str` types according to
-[Unicode Standard Annex #11][UAX11] rules.
+[![Build status](https://github.com/unicode-rs/unicode-width/actions/workflows/rust.yml/badge.svg)](https://travis-ci.org/unicode-rs/unicode-width)
+[![crates.io version](https://img.shields.io/crates/v/unicode-width)](https://crates.io/crates/unicode-width)
+[![Docs status](https://img.shields.io/docsrs/unicode-width)](https://docs.rs/unicode-width/)
 
-[UAX11]: http://www.unicode.org/reports/tr11/
+Determine displayed width of `char` and `str` types according to [Unicode Standard Annex #11][UAX11],
+other portions of the Unicode standard, and common implementations of POSIX [`wcwidth()`](https://pubs.opengroup.org/onlinepubs/9699919799/).
 
-[![Build Status](https://travis-ci.org/unicode-rs/unicode-width.svg)](https://travis-ci.org/unicode-rs/unicode-width)
+This crate is `#![no_std]`.
 
-[Documentation](https://unicode-rs.github.io/unicode-width/unicode_width/index.html)
+[UAX11]: http://www.unicode.org/reports/tr11/
 
 ```rust
-extern crate unicode_width;
-
 use unicode_width::UnicodeWidthStr;
 
 fn main() {
@@ -45,17 +45,12 @@ and nonstandard [Korean jamo](https://unicode.org/glossary/#jamo) sequences may
 be rendered with a different width than what this crate says. (This is not an
 exhaustive list.)
 
-## features
-
-unicode-width does not depend on libstd, so it can be used in crates
-with the `#![no_std]` attribute.
-
 ## crates.io
 
 You can use this package in your project by adding the following
 to your `Cargo.toml`:
 
 ```toml
 [dependencies]
-unicode-width = "0.1.7"
+unicode-width = "0.1.11"
 ```

src/lib.rs

@@ -9,40 +9,71 @@
 // except according to those terms.
 
 //! Determine displayed width of `char` and `str` types according to
-//! [Unicode Standard Annex #11](http://www.unicode.org/reports/tr11/)
-//! rules.
+//! [Unicode Standard Annex #11](http://www.unicode.org/reports/tr11/),
+//! other portions of the Unicode standard, and common implementations of
+//! POSIX [`wcwidth()`](https://pubs.opengroup.org/onlinepubs/9699919799/).
+//! See the [Rules for determining width](#rules-for-determining-width) section
+//! for the exact rules.
 //!
-//! ```rust
-//! extern crate unicode_width;
+//! This crate is `#![no_std]`.
 //!
+//! ```rust
 //! use unicode_width::UnicodeWidthStr;
 //!
-//! fn main() {
-//!     let teststr = "Ｈｅｌｌｏ, ｗｏｒｌｄ!";
-//!     let width = UnicodeWidthStr::width(teststr);
-//!     println!("{}", teststr);
-//!     println!("The above string is {} columns wide.", width);
-//!     let width = teststr.width_cjk();
-//!     println!("The above string is {} columns wide (CJK).", width);
-//! }
+//! let teststr = "Ｈｅｌｌｏ, ｗｏｒｌｄ!";
+//! let width = UnicodeWidthStr::width(teststr);
+//! println!("{}", teststr);
+//! println!("The above string is {} columns wide.", width);
+//! let width = teststr.width_cjk();
+//! println!("The above string is {} columns wide (CJK).", width);
 //! ```
 //!
-//! # features
+//! # Rules for determining width
 //!
-//! unicode-width does not depend on `std`, so it can be used in crates
-//! with the `#![no_std]` attribute.
+//! This crate currently uses the following rules to determine the width of a
+//! character or string, in order of decreasing precedence. These may be tweaked in the future.
 //!
-//! # crates.io
+//! 1. [`'\u{00AD}'` SOFT HYPHEN](https://util.unicode.org/UnicodeJsps/character.jsp?a=00AD) has width 1.
+//! 2. [`'\u{115F}'` HANGUL CHOSEONG FILLER](https://util.unicode.org/UnicodeJsps/character.jsp?a=115F) has width 2.
+//! 3. The following have width 0:
+//!    - [Characters](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5Cp%7BDefault_Ignorable_Code_Point%7D)
+//!       with the [`Default_Ignorable_Code_Point`](https://www.unicode.org/versions/Unicode15.0.0/ch05.pdf#G40095) property.
+//!    - [Characters](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5Cp%7BGrapheme_Extend%7D)
+//!       with the [`Grapheme_Extend`] property.
+//!    - The following 8 characters, all of which have NFD decompositions consisting of two [`Grapheme_Extend`] chracters:
+//!      - [`'\u{0CC0}'` KANNADA VOWEL SIGN II](https://util.unicode.org/UnicodeJsps/character.jsp?a=0CC0),
+//!      - [`'\u{0CC7}'` KANNADA VOWEL SIGN EE](https://util.unicode.org/UnicodeJsps/character.jsp?a=0CC7),
+//!      - [`'\u{0CC8}'` KANNADA VOWEL SIGN AI](https://util.unicode.org/UnicodeJsps/character.jsp?a=0CC8),
+//!      - [`'\u{0CCA}'` KANNADA VOWEL SIGN O](https://util.unicode.org/UnicodeJsps/character.jsp?a=0CCA),
+//!      - [`'\u{0CCB}'` KANNADA VOWEL SIGN OO](https://util.unicode.org/UnicodeJsps/character.jsp?a=0CCB),
+//!      - [`'\u{1B3B}'` BALINESE VOWEL SIGN RA REPA TEDUNG](https://util.unicode.org/UnicodeJsps/character.jsp?a=1B3B),
+//!      - [`'\u{1B3D}'` BALINESE VOWEL SIGN LA LENGA TEDUNG](https://util.unicode.org/UnicodeJsps/character.jsp?a=1B3D), and
+//!      - [`'\u{1B43}'` BALINESE VOWEL SIGN PEPET TEDUNG](https://util.unicode.org/UnicodeJsps/character.jsp?a=1B43).
+//!    - [Characters](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5Cp%7BHangul_Syllable_Type%3DV%7D%5Cp%7BHangul_Syllable_Type%3DT%7D)
+//!       with a [`Hangul_Syllable_Type`](https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G45593)
+//!       of `Vowel_Jamo` (`V`) or `Trailing_Jamo` (`T`).
+//!    - [`'\0'` NUL](https://util.unicode.org/UnicodeJsps/character.jsp?a=0000).
+//! 4. The [control characters](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5Cp%7BCc%7D)
+//!    have no defined width, and are ignored when determining the width of a string.
+//! 5. [Characters](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5Cp%7BEast_Asian_Width%3DF%7D%5Cp%7BEast_Asian_Width%3DW%7D)
+//!    with an [`East_Asian_Width`] of [`Fullwidth` (`F`)](https://www.unicode.org/reports/tr11/#ED2)
+//!    or [`Wide` (`W`)](https://www.unicode.org/reports/tr11/#ED4) have width 2.
+//! 6. [Characters](https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5Cp%7BEast_Asian_Width%3DA%7D)
+//!    with an [`East_Asian_Width`] of [`Ambiguous` (`A`)](https://www.unicode.org/reports/tr11/#ED6)
+//!    have width 2 in an East Asian context, and width 1 otherwise.
+//! 7. All other characters have width 1.
 //!
-//! You can use this package in your project by adding the following
-//! to your `Cargo.toml`:
+//! [`East_Asian_Width`]: https://www.unicode.org/reports/tr11/#ED1
+//! [`Grapheme_Extend`]: https://www.unicode.org/versions/Unicode15.0.0/ch03.pdf#G52443
+
 //!
-//! ```toml
-//! [dependencies]
-//! unicode-width = "0.1.5"
-//! ```
+//! ## Canonical equivalence
+//!
+//! The non-CJK width methods guarantee that canonically equivalent strings are assigned the same width.
+//! However, this guarantee does not currently hold for the CJK width variants.
 
-#![deny(missing_docs, unsafe_code)]
+#![forbid(unsafe_code)]
+#![deny(missing_docs)]
 #![doc(
     html_logo_url = "https://unicode-rs.github.io/unicode-rs_sm.png",
     html_favicon_url = "https://unicode-rs.github.io/unicode-rs_sm.png"