translation using NGettext.Wpf

src/MpvNet.Windows/WPF/WpfTranslator.cs

@@ -0,0 +1,63 @@
+
+using NGettext.Wpf;
+
+using System.Globalization;
+
+namespace MpvNet.Windows.WPF;
+
+public class WpfTranslator : ITranslator
+{
+    static Language[] Languages { get; } = new Language[] {
+        new("english", "en", "en"),
+        new("chinese-china", "zh-Hans", "zh"),  // Chinese (Simplified)
+        new("german", "de", "de"),
+    };
+
+    public string Gettext(string msgId)
+    {
+        InitNGettextWpf();
+        return Translation._(msgId);
+    }
+
+    void InitNGettextWpf()
+    {
+        if (Translation.Localizer == null)
+            CompositionRoot.Compose("mpvnet", GetCulture(App.Language), Folder.Startup + "Locale");
+    }
+
+    string GetSystemLanguage()
+    {
+        string twoLetterName = CultureInfo.CurrentUICulture.TwoLetterISOLanguageName;
+
+        if (twoLetterName == "zh")
+            return "chinese-china";  // Chinese (Simplified)
+
+        return new CultureInfo(twoLetterName).EnglishName.ToLowerInvariant();
+    }
+
+    CultureInfo GetCulture(string name)
+    {
+        if (name == "system")
+            name = GetSystemLanguage();
+
+        foreach (Language lang in Languages)
+            if (lang.MpvNetName == name)
+                return new CultureInfo(lang.CultureInfoName);
+
+        throw new Exception($"Unknown language {name}.");
+    }
+
+    class Language
+    {
+        public string MpvNetName { get; }
+        public string CultureInfoName { get; }
+        public string TwoLetterName { get; }
+
+        public Language(string mpvNetName, string cultureInfoName, string twoLetterName)
+        {
+            MpvNetName = mpvNetName;
+            CultureInfoName = cultureInfoName;
+            TwoLetterName = twoLetterName;
+        }
+    }
+}