Unicode::DisplayWidth ↑

Determines the monospace display width of a string in Ruby. Implementation based on EastAsianWidth.txt and other data, 100% in Ruby. It does not rely on the OS vendor (like wcwidth()) to provide an up-to-date method for measuring string width.

Unicode version: 15.0.0 (September 2022)

Supported Rubies: 3.1, 3.0, 2.7

Old Rubies which might still work: 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9

Version 2.0 — Breaking Changes ↑

Some features of this library were marked deprecated for a long time and have been removed with Version 2.0:

If you are relying on the String#display_width string extension to be automatically loaded (old behavior), please load it explicitly now:

require "unicode/display_width/string_ext"

You could also change your Gemfile line to achieve this:

gem "unicode-display_width", require: "unicode/display_width/string_ext"

Introduction to Character Widths ↑

Guessing the correct space a character will consume on terminals is not easy. There is no single standard. Most implementations combine data from East Asian Width, some General Categories, and hand-picked adjustments.

How this Library Handles Widths ↑

Further at the top means higher precedence. Please expect changes to this algorithm with every MINOR version update (the X in 1.X.0)!

Width | Characters | Comment ——-|——————————|————————————————– X | (user defined) | Overwrites any other values -1 | "\b" | Backspace (total width never below 0) 0 | "\0", "\x05", "\a", "\n", "\v", "\f", "\r", "\x0E", "\x0F" | C0 control codes that do not change horizontal width 1 | "\u{00AD}" | SOFT HYPHEN 2 | "\u{2E3A}" | TWO-EM DASH 3 | "\u{2E3B}" | THREE-EM DASH 0 | General Categories: Mn, Me, Cf (non-arabic) | Excludes ARABIC format characters 0 | "\u{1160}".."\u{11FF}", "\u{D7B0}".."\u{D7FF}" | HANGUL JUNGSEONG 0 | "\u{2060}".."\u{206F}", "\u{FFF0}".."\u{FFF8}", "\u{E0000}".."\u{E0FFF}" | Ignorable ranges 2 | East Asian Width: F, W | Full-width characters 2 | "\u{3400}".."\u{4DBF}", "\u{4E00}".."\u{9FFF}", "\u{F900}".."\u{FAFF}", "\u{20000}".."\u{2FFFD}", "\u{30000}".."\u{3FFFD}" | Full-width ranges 1 or 2 | East Asian Width: A | Ambiguous characters, user defined, default: 1 1 | All other codepoints | -

Install ↑

Install the gem with:

$ gem install unicode-display_width

Or add to your Gemfile:

gem 'unicode-display_width'

Usage ↑

Classic API ↑

require 'unicode/display_width'

Unicode::DisplayWidth.of("⚀") # => 1
Unicode::DisplayWidth.of("一") # => 2

Ambiguous Characters ↑

The second parameter defines the value returned by characters defined as ambiguous:

Unicode::DisplayWidth.of("·", 1) # => 1
Unicode::DisplayWidth.of("·", 2) # => 2

Custom Overwrites ↑

You can overwrite how to handle specific code points by passing a hash (or even a proc) as third parameter:

Unicode::DisplayWidth.of("a\tb", 1, "\t".ord => 10))

Emoji Support ↑

Emoji width support is included, but in must be activated manually. It will adjust the string's size for modifier and zero-width joiner sequences. You also need to add the unicode-emoji gem to your Gemfile:

gem 'unicode-display_width'
gem 'unicode-emoji'

Enable the emoji string width adjustments by passing emoji: true as fourth parameter:

Unicode::DisplayWidth.of "🤾🏽‍♀️" # => 5
Unicode::DisplayWidth.of "🤾🏽‍♀️", 1, {}, emoji: true # => 2

Usage with String Extension ↑

require 'unicode/display_width/string_ext'

"⚀".display_width # => 1
'一'.display_width # => 2

Modern API: Keyword-arguments Based Config Object ↑

Version 2.0 introduces a keyword-argument based API, which allows you to save your configuration for later-reuse. This requires an extra line of code, but has the advantage that you'll need to define your string-width options only once:

require 'unicode/display_width'

display_width = Unicode::DisplayWidth.new(
  # ambiguous: 1,
  overwrite: { "A".ord => 100 },
  emoji: true,
)

display_width.of "⚀" # => 1
display_width.of "🤾🏽‍♀️" # => 2
display_width.of "A" # => 100

Usage From the CLI ↑

Use this one-liner to print out display widths for strings from the command-line:

$ gem install unicode-display_width
$ ruby -r unicode/display_width -e 'puts Unicode::DisplayWidth.of $*[0]' -- "一"

Replace “一” with the actual string to measure

Other Implementations & Discussion ↑

See unicode-x for more Unicode related micro libraries.

Copyright & Info ↑