string_width

gleam add string_width@1

import string_width

pub fn main() {
  string_width.dimensions("hello,\n안녕하세요", [])
  // --> #(2, 10)

  string_width.line("👩‍👩‍👦‍👦", [string_width.HandleGraphemeClusters])
  // --> 2
}

A small package estimates the required number of cells when printing a string on the terminal. It supports all Gleam targets.

Limitations

• Many terminals don’t support grapheme clusters properly, so by default, the values returned by this library try to match the behaviour of libc instead of modern text rendering pipelines.

• The width of many characters is context-dependent and may vary based on the current locale, selected font, operating system, or surrounding context; The numbers reported by the functions in this library may not be fully accurate.

  If you encounter a mismatch that is consistent across multiple environments, feel free to open an issue or ping me on Discord!

• The behaviour when encountering variant selectors does not match other similar libraries.

Sources

This library is heavily based on musl libc wcwidth implementation, the ansi-regex npm package, and uses many of the test cases of the string-width npm package.

• UAX #11 East Asian Width: https://www.unicode.org/reports/tr11/
• Grapheme Clusters in Terminals: https://mitchellh.com/writing/grapheme-clusters-in-terminals
• get-east-asian-width: https://github.com/sindresorhus/get-east-asian-width
• string-width: https://github.com/sindresorhus/string-width
• ansi-regex: https://github.com/chalk/ansi-regex
• musl-libc wcwidth: https://git.musl-libc.org/cgit/musl/tree/src/ctype/wcwidth.c
• glibc wcwidth: https://sourceware.org/git/?p=glibc.git;a=blob;f=wcsmbs/wcwidth.h;hb=HEAD