Crate east_asian_width 

East Asian Width

A Rust library for determining the display width of Unicode characters in East Asian contexts. This is particularly useful for terminal applications, text editors, and other software that needs to properly align text containing CJK (Chinese, Japanese, Korean) characters.

Features

• Fast lookups: Pre-generated lookup tables for O(1) character width determination
• Unicode compliant: Based on the official Unicode East Asian Width property
• Flexible API: Support for both simple and configurable width calculations
• Zero dependencies: No runtime dependencies for the core library

Usage

Basic Usage

use east_asian_width::{east_asian_width, east_asian_width_type, DisplayWidth};

// Get the display width of a character
assert_eq!(east_asian_width('A' as u32), DisplayWidth::Narrow);  // Narrow/Neutral = 1
assert_eq!(east_asian_width('字' as u32), DisplayWidth::Wide); // Wide = 2

// Convert to numeric values when needed
assert_eq!(east_asian_width('A' as u32).as_u8(), 1);
assert_eq!(east_asian_width('字' as u32).as_u8(), 2);

// Get the East Asian Width category
assert_eq!(east_asian_width_type('A' as u32), "narrow");
assert_eq!(east_asian_width_type('字' as u32), "wide");

Handling Ambiguous Characters

Some characters are classified as “ambiguous” and can be displayed as either narrow or wide depending on the context. You can control this behavior:

use east_asian_width::{east_asian_width, DisplayWidth};

let ambiguous_char = 0x00A1; // ¡ (inverted exclamation mark)

// Default: ambiguous characters are treated as narrow (width 1)
assert_eq!(east_asian_width(ambiguous_char), DisplayWidth::Narrow);

// Treat ambiguous characters as wide (width 2)
assert_eq!(east_asian_width((ambiguous_char, true)), DisplayWidth::Wide);

// Convert to numeric values
assert_eq!(east_asian_width(ambiguous_char).as_u8(), 1);
assert_eq!(east_asian_width((ambiguous_char, true)).as_u8(), 2);

Character Categories

The library recognizes six East Asian Width categories:

• Narrow (Na): Characters that are always narrow (width 1)
• Neutral (N): Characters that don’t have East Asian context (width 1)
• Halfwidth (H): Characters that are narrow in East Asian context (width 1)
• Ambiguous (A): Characters that can be narrow or wide depending on context
• Wide (W): Characters that are always wide (width 2)
• Fullwidth (F): Characters that are wide in East Asian context (width 2)

Re-exports

pub use error::EastAsianWidthError;

pub use error::validate_code_point;

pub use lookup::is_ambiguous;

pub use lookup::is_full_width;

pub use lookup::is_wide;

Modules

error

Error types and validation functions for East Asian Width operations.

lookup

Contains the generated Unicode lookup tables and functions.

Enums

DisplayWidth

Represents the display width of a character in East Asian contexts

Traits

EastAsianWidthInput

Trait to allow different parameter types for the east_asian_width function.

Functions

east_asian_width

Returns the display width of a Unicode code point in East Asian contexts

east_asian_width_type

Returns the East Asian Width category for a Unicode code point

try_east_asian_width

Fallible version of east_asian_width

try_east_asian_width_type

Fallible version of east_asian_width_type