sys_language

A cross-platform Rust library for detecting the system's default language with support for preferred language selection and fallback mechanisms.

Authors

Cupnfish
z.ai

Features

🌍 Cross-platform Support: Works on Windows, macOS, and Linux
🎯 Smart Matching: Supports exact matching and primary language matching
⚡ Flexible Configuration: Supports preferred language lists and fallback language settings
🔧 Easy to Use: Provides simple API and convenience functions

Installation

Add the dependency to your Cargo.toml:

[dependencies]

sys_language = "0.1.0"

Usage

Basic Usage

use sys_language::detect_system_language;

let language = detect_system_language();
println!("System language: {}", language);
println!("Primary language: {}", language.primary_language());

Advanced Usage

use sys_language::LanguageDetector;

let detector = LanguageDetector::new()
    .with_preferred_languages(&["zh-CN", "en-US", "ja-JP"])
    .with_fallback("en-US");

let language = detector.detect();
println!("Detected language: {}", language);

Using Convenience Functions

use sys_language::detect_language_with_options;

let preferred = ["zh-CN", "en-US"];
let fallback = "en-US";
let language = detect_language_with_options(&preferred, fallback);
println!("Best language: {}", language);

Language Matching Rules

The library supports intelligent language matching, including:

Exact Matching: zh-CN exactly matches zh-CN
Primary Language Matching: zh-CN matches zh
Same Primary Language: zh-CN matches zh-TW

use sys_language::Language;

let lang = Language::new("zh-CN");

assert!(lang.matches("zh-CN"));  // Exact match
assert!(lang.matches("zh"));     // Primary language match
assert!(lang.matches("zh-TW"));  // Same primary language
assert!(!lang.matches("en-US")); // No match

Platform-Specific Implementations

Windows

Uses Windows API (GetUserDefaultLocaleName) to get system language settings.

macOS

Reads language settings from environment variables (LANG, LC_ALL, LC_CTYPE).

Linux

Reads language settings from environment variables (LANG, LC_ALL, LANGUAGE), with support for colon-separated language lists.

Example Program

Run the example program to see all features in action:

cargo run --example basic_usage

Example output:

=== System Language Detection Example ===

1. Detect system default language:
   System language: zh-CN
   Primary language: zh
   Region: CN

2. Using LanguageDetector:
   Detected language: zh-CN
   Preferred languages: ["zh-CN", "zh-TW", "en-US"]
   Fallback language: en-US

3. Test language matching logic:
   Case 1 (preferred: zh-CN, en-US): zh-CN
   Case 2 (preferred: zh-CN, ja-JP): zh-CN
   Case 3 (no preferred languages): fr-FR

4. Using convenience functions:
   Preferred: ["de-DE", "fr-FR", "es-ES"], Fallback: en-US
   Result: de-DE

5. Language matching rules demonstration:
   'zh-CN' matches 'zh-CN'? true
   'zh-CN' matches 'zh'? true
   'zh-CN' matches 'zh-TW'? true
   'zh-CN' matches 'en-US'? false

=== Example End ===

API Documentation

Language Struct

pub struct Language {
    code: String,
}

Methods:

new(code: &str) -> Language - Create a new language instance
as_str(&self) -> &str - Get the language code as a string
primary_language(&self) -> &str - Get the primary language part
region(&self) -> Option<&str> - Get the region part
matches(&self, other: &str) -> bool - Check if it matches the specified language

LanguageDetector Struct

pub struct LanguageDetector {
    preferred_languages: Vec<String>,
    fallback: String,
}