Add translations for 16 languages

DesktopClock.Tests/LocalizationTests.cs

@@ -0,0 +1,147 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Resources;
+using System.Text.RegularExpressions;
+
+namespace DesktopClock.Tests;
+
+public class LocalizationTests
+{
+    private const string ResourcePrefix = "DesktopClock.Localization.Strings.";
+
+    private static readonly Regex PlaceholderRegex = new(@"\{[^{}]*\}");
+    private static readonly Regex UrlRegex = new(@"https://[\w./-]*\w");
+
+    // Alt access keys that share a window must not collide.
+    private static readonly string[][] AccessKeyGroups =
+    {
+        ["MenuCopy", "MenuHide", "MenuAlwaysOnTop", "MenuSettings", "MenuCheckForUpdates", "MenuGiveFeedback", "MenuExit"],
+        ["NavDisplay", "NavCountdown", "NavWindow", "NavThemePresets", "NavTypography", "NavAppearance", "NavAlerts", "NavShortcuts", "NavDiscoverMore", "NavCredits", "SettingsFolder", "SettingsFile", "NewClock"],
+    };
+
+    private static readonly Dictionary<string, string> English = ReadStrings("");
+
+    public static IEnumerable<object[]> Translations =>
+        typeof(Loc).Assembly.GetManifestResourceNames()
+            .Where(n => n.StartsWith(ResourcePrefix) && n != ResourcePrefix + "resources")
+            .Select(n => new object[] { n.Substring(ResourcePrefix.Length, n.Length - ResourcePrefix.Length - ".resources".Length) });
+
+    [Fact]
+    public void Translations_AreEmbeddedInTheExe()
+    {
+        Assert.NotEmpty(Translations);
+        Assert.Equal("_Copy", Loc.Get("MenuCopy", CultureInfo.GetCultureInfo("en-US")));
+    }
+
+    [Theory]
+    [MemberData(nameof(Translations))]
+    public void Translation_HasTheSameKeysAsEnglish(string culture)
+    {
+        var translation = ReadStrings(culture + ".");
+
+        Assert.Empty(English.Keys.Except(translation.Keys));
+        Assert.Empty(translation.Keys.Except(English.Keys));
+        Assert.DoesNotContain(translation, t => string.IsNullOrWhiteSpace(t.Value));
+    }
+
+    [Theory]
+    [MemberData(nameof(Translations))]
+    public void Translation_KeepsPlaceholdersAndLinks(string culture)
+    {
+        foreach (var translated in ReadStrings(culture + "."))
+        {
+            var english = English[translated.Key];
+            Assert.True(Placeholders(english).SetEquals(Placeholders(translated.Value)), $"{culture} {translated.Key}: placeholders changed in \"{translated.Value}\"");
+
+            foreach (Match url in UrlRegex.Matches(english))
+                Assert.True(translated.Value.Contains(url.Value), $"{culture} {translated.Key}: missing {url.Value}");
+        }
+    }
+
+    [Theory]
+    [MemberData(nameof(Translations))]
+    public void Translation_HasOneUniqueAccessKeyPerLabel(string culture)
+    {
+        var translation = ReadStrings(culture + ".");
+
+        foreach (var key in English.Keys.Where(k => English[k].Contains('_')))
+        {
+            var value = translation[key];
+            var underscore = value.IndexOf('_');
+            Assert.True(underscore >= 0 && underscore == value.LastIndexOf('_') && underscore < value.Length - 1 && char.IsLetterOrDigit(value[underscore + 1]),
+                $"{culture} {key}: \"{value}\" needs exactly one underscore before a letter");
+        }
+
+        foreach (var group in AccessKeyGroups)
+        {
+            var letters = group.Select(k => char.ToUpperInvariant(translation[k][translation[k].IndexOf('_') + 1])).ToList();
+            Assert.True(letters.Distinct().Count() == letters.Count, $"{culture}: duplicate access keys in {string.Join(", ", group)}");
+        }
+    }
+
+    [Theory]
+    [MemberData(nameof(Translations))]
+    public void Translation_HasPluralFormsForItsLanguage(string culture)
+    {
+        var expectedForms = CultureInfo.GetCultureInfo(culture).TwoLetterISOLanguageName switch
+        {
+            "pl" or "ru" or "uk" => 3,
+            "id" or "ja" or "ko" or "tr" or "vi" or "zh" => 1,
+            _ => 2,
+        };
+
+        foreach (var plural in ReadStrings(culture + ".").Where(t => English[t.Key].Contains('|')))
+            Assert.True(plural.Value.Split('|').Length == expectedForms, $"{culture} {plural.Key}: expected {expectedForms} forms in \"{plural.Value}\"");
+    }
+
+    [Fact]
+    public void Get_FallsBackToTheClosestTranslationThenEnglish()
+    {
+        var german = ReadStrings("de.");
+
+        Assert.Equal(german["MenuCopy"], Loc.Get("MenuCopy", CultureInfo.GetCultureInfo("de-AT")));
+        Assert.Equal("_Copy", Loc.Get("MenuCopy", CultureInfo.GetCultureInfo("sv-SE")));
+        Assert.Equal("NoSuchKey", Loc.Get("NoSuchKey"));
+    }
+
+    [Fact]
+    public void Source_OnlyUsesKeysThatExist()
+    {
+        var sourceFolder = FindSourceFolder();
+        var usage = new Regex(@"Loc\.(?:Get|Format)\(""(\w+)""|=""\{local:Loc (\w+)\}""|""(Relative\w+)""");
+        var used = Directory.EnumerateFiles(sourceFolder, "*.*", SearchOption.AllDirectories)
+            .Where(f => f.EndsWith(".cs") || f.EndsWith(".xaml"))
+            .Where(f => !f.Contains($"{Path.DirectorySeparatorChar}obj{Path.DirectorySeparatorChar}"))
+            .SelectMany(f => usage.Matches(File.ReadAllText(f)).Cast<Match>())
+            .Select(m => m.Groups.Cast<Group>().Skip(1).First(g => g.Success).Value)
+            .Distinct()
+            .ToList();
+
+        Assert.NotEmpty(used);
+        Assert.DoesNotContain(used, k => !English.ContainsKey(k));
+    }
+
+    private static HashSet<string> Placeholders(string text) => new(PlaceholderRegex.Matches(text).Cast<Match>().Select(m => m.Value));
+
+    private static Dictionary<string, string> ReadStrings(string culturePart)
+    {
+        using var stream = typeof(Loc).Assembly.GetManifestResourceStream($"{ResourcePrefix}{culturePart}resources");
+        using var reader = new ResourceReader(stream);
+        return reader.Cast<DictionaryEntry>().ToDictionary(e => (string)e.Key, e => (string)e.Value);
+    }
+
+    private static string FindSourceFolder()
+    {
+        for (var dir = new DirectoryInfo(AppDomain.CurrentDomain.BaseDirectory); dir != null; dir = dir.Parent)
+        {
+            if (File.Exists(Path.Combine(dir.FullName, "DesktopClock.sln")))
+                return Path.Combine(dir.FullName, "DesktopClock");
+        }
+
+        throw new DirectoryNotFoundException("Couldn't find the solution folder.");
+    }
+}

DesktopClock.Tests/RelativeTimeFormatterTests.cs

@@ -1,7 +1,9 @@
 using System;
+using System.Globalization;
 
 namespace DesktopClock.Tests;
 
+[UseUICulture("en-US")]
 public class RelativeTimeFormatterTests
 {
     private static readonly DateTime Now = new(2026, 3, 15, 12, 34, 56, 500);
@@ -92,4 +94,25 @@ public void Format_IgnoresDateTimeKind()
 
         Assert.Equal("in 3 hours", RelativeTimeFormatter.Format(target, now));
     }
+
+    [Theory]
+    [InlineData("de", "00:01:00", "in einer Minute")]
+    [InlineData("de", "3.00:00:00", "in 3 Tagen")]
+    [InlineData("fr", "01:00:00", "dans une heure")]
+    [InlineData("ja", "03:00:00", "3時間後")]
+    [InlineData("zh-CN", "2.00:00:00", "2天后")]
+    [InlineData("pl", "00:01:00", "za minutę")]
+    [InlineData("pl", "00:12:00", "za 12 minut")]
+    [InlineData("pl", "00:22:00", "za 22 minuty")]
+    [InlineData("ru", "11.00:00:00", "через 11 дней")]
+    [InlineData("ru", "21.00:00:00", "через 21 день")]
+    [InlineData("ru", "22.00:00:00", "через 22 дня")]
+    [InlineData("ru", "25.00:00:00", "через 25 дней")]
+    [InlineData("uk", "00:03:00", "через 3 хвилини")]
+    public void Format_UsesTheLanguagesPluralForms(string culture, string offset, string expected)
+    {
+        var target = Now + TimeSpan.Parse(offset);
+
+        Assert.Equal(expected, RelativeTimeFormatter.Format(target, Now, CultureInfo.GetCultureInfo(culture)));
+    }
 }

DesktopClock.Tests/TimeStringFormatterTests.cs

@@ -3,6 +3,7 @@
 
 namespace DesktopClock.Tests;
 
+[UseUICulture("en-US")]
 public class TimeStringFormatterTests
 {
     [Fact]

DesktopClock.Tests/UseUICultureAttribute.cs

@@ -0,0 +1,25 @@
+using System.Globalization;
+using System.Reflection;
+using System.Threading;
+using Xunit.Sdk;
+
+namespace DesktopClock.Tests;
+
+/// <summary>
+/// Runs a test with the given UI language so text assertions don't depend on the machine's display language.
+/// </summary>
+public sealed class UseUICultureAttribute(string culture) : BeforeAfterTestAttribute
+{
+    private CultureInfo _originalCulture;
+
+    public override void Before(MethodInfo methodUnderTest)
+    {
+        _originalCulture = Thread.CurrentThread.CurrentUICulture;
+        Thread.CurrentThread.CurrentUICulture = CultureInfo.GetCultureInfo(culture);
+    }
+
+    public override void After(MethodInfo methodUnderTest)
+    {
+        Thread.CurrentThread.CurrentUICulture = _originalCulture;
+    }
+}

DesktopClock/ClockTheme.cs

@@ -45,25 +45,25 @@ public static IReadOnlyList<ClockTheme> GetBuiltInThemes()
         return new[]
         {
             CreateSystemTheme(),
-            new ClockTheme("Accent", "Segoe UI", "SemiBold",
+            new ClockTheme(Loc.Get("ThemeAccent"), "Segoe UI", "SemiBold",
                 Color.FromRgb(0xFF, 0xFF, 0xFF), SystemThemeService.GetSystemAccentColor(),
                 backgroundEnabled: true, backgroundOpacity: 1, backgroundCornerRadius: 1, outlineThickness: 0.2),
-            new ClockTheme("Smoke", "Segoe UI", "Normal",
+            new ClockTheme(Loc.Get("ThemeSmoke"), "Segoe UI", "Normal",
                 Color.FromRgb(0xF2, 0xF2, 0xF2), Color.FromRgb(0x0A, 0x0A, 0x10),
                 backgroundEnabled: true, backgroundOpacity: 0.55, backgroundCornerRadius: 1, outlineThickness: 0.2),
-            new ClockTheme("Terminal", "Consolas", "Bold",
+            new ClockTheme(Loc.Get("ThemeTerminal"), "Consolas", "Bold",
                 Color.FromRgb(0x00, 0xE5, 0xFF), Color.FromRgb(0x0C, 0x0C, 0x0C),
                 backgroundEnabled: true, backgroundOpacity: 0.85, backgroundCornerRadius: 1, outlineThickness: 0.2),
-            new ClockTheme("Midnight", "Segoe UI", "SemiBold",
+            new ClockTheme(Loc.Get("ThemeMidnight"), "Segoe UI", "SemiBold",
                 Color.FromRgb(0x4C, 0xC2, 0xFF), Color.FromRgb(0x1B, 0x1B, 0x1B),
                 backgroundEnabled: true, backgroundOpacity: 0.95, backgroundCornerRadius: 1, outlineThickness: 0.2),
-            new ClockTheme("Paper", "Georgia", "Normal",
+            new ClockTheme(Loc.Get("ThemePaper"), "Georgia", "Normal",
                 Color.FromRgb(0x1A, 0x1A, 0x1A), Color.FromRgb(0xFA, 0xF9, 0xF6),
                 backgroundEnabled: true, backgroundOpacity: 0.97, backgroundCornerRadius: 1, outlineThickness: 0.2),
-            new ClockTheme("Minimal", "Segoe UI", "Light",
+            new ClockTheme(Loc.Get("ThemeMinimal"), "Segoe UI", "Light",
                 Color.FromRgb(0xFF, 0xFF, 0xFF), Color.FromRgb(0x00, 0x00, 0x00),
                 backgroundEnabled: false, backgroundOpacity: 1, backgroundCornerRadius: 1, outlineThickness: 0),
-            new ClockTheme("Chalk", "Segoe UI", "SemiBold",
+            new ClockTheme(Loc.Get("ThemeChalk"), "Segoe UI", "SemiBold",
                 Color.FromRgb(0xFF, 0xFF, 0xFF), Color.FromRgb(0x00, 0x00, 0x00),
                 backgroundEnabled: false, backgroundOpacity: 1, backgroundCornerRadius: 1, outlineThickness: 1.5),
         };
@@ -101,7 +101,7 @@ private static ClockTheme CreateSystemTheme()
             outerColor = Color.FromRgb(247, 247, 247);
         }
 
-        return new ClockTheme("System", "Consolas", "Normal", textColor, outerColor,
+        return new ClockTheme(Loc.Get("ThemeSystem"), "Consolas", "Normal", textColor, outerColor,
             backgroundEnabled: true, backgroundOpacity: 0.9, backgroundCornerRadius: 1, outlineThickness: 0.2);
     }
 }

DesktopClock/CountdownTargetEditor.xaml

@@ -1,15 +1,16 @@
 <UserControl x:Class="DesktopClock.CountdownTargetEditor"
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:local="clr-namespace:DesktopClock"
              xmlns:p="clr-namespace:DesktopClock.Properties">
     <StackPanel>
         <!-- One-click targets for common scenarios, computed when clicked -->
-        <TextBlock Text="Common targets"
+        <TextBlock Text="{local:Loc CommonTargets}"
                    Style="{StaticResource EditorCaption}" />
         <WrapPanel x:Name="PresetsPanel"
                    Margin="0,0,0,10" />
 
-        <TextBlock Text="Custom target"
+        <TextBlock Text="{local:Loc CustomTarget}"
                    Style="{StaticResource EditorCaption}" />
         <Grid Margin="0,0,0,10">
             <Grid.ColumnDefinitions>
@@ -20,7 +21,7 @@
             <TextBox Grid.Column="0"
                      Text="{Binding CountdownTo, Source={x:Static p:Settings.Default}, Mode=TwoWay}" />
             <Button Grid.Column="2"
-                    Content="Reset"
+                    Content="{local:Loc Reset}"
                     Click="ResetTarget" />
         </Grid>
 
@@ -31,7 +32,7 @@
                 CornerRadius="{DynamicResource ControlCornerRadius}"
                 Padding="10,7">
             <StackPanel>
-                <TextBlock Text="Preview"
+                <TextBlock Text="{local:Loc Preview}"
                            FontSize="12"
                            Foreground="{DynamicResource TextSecondaryBrush}"
                            Margin="0,0,0,2" />

DesktopClock/CountdownTargetEditor.xaml.cs

@@ -16,10 +16,10 @@ public partial class CountdownTargetEditor : UserControl
 {
     private static readonly (string Name, Func<DateTime> GetTarget)[] Presets =
     {
-        ("Midnight tonight", () => DateTime.Today.AddDays(1)),
-        ("Tomorrow morning", () => DateTime.Today.AddDays(1).AddHours(9)),
-        ("Friday afternoon", () => NextOccurrence(DayOfWeek.Friday, 17)),
-        ("New Year", () => new DateTime(DateTime.Today.Year + 1, 1, 1)),
+        (Loc.Get("TargetMidnight"), () => DateTime.Today.AddDays(1)),
+        (Loc.Get("TargetTomorrowMorning"), () => DateTime.Today.AddDays(1).AddHours(9)),
+        (Loc.Get("TargetFridayAfternoon"), () => NextOccurrence(DayOfWeek.Friday, 17)),
+        (Loc.Get("TargetNewYear"), () => new DateTime(DateTime.Today.Year + 1, 1, 1)),
     };
 
     private bool _built;
@@ -101,7 +101,7 @@ private void UpdatePreview()
         var target = Settings.Default.CountdownTo;
 
         PreviewText.Text = target == default
-            ? "No target. The clock shows the current time."
+            ? Loc.Get("NoCountdownTarget")
             : $"{target:f} — {RelativeTimeFormatter.Format(target, DateTime.Now)}";
     }
 

DesktopClock/DesktopClock.csproj

@@ -28,4 +28,9 @@
   <ItemGroup>
     <Resource Include="DesktopClock.ico" />
   </ItemGroup>
+
+  <ItemGroup>
+    <!-- Translations compile into the exe instead of satellite assemblies, which Costura doesn't embed, so the app stays a single file. See Loc. -->
+    <EmbeddedResource Update="Localization\Strings.*.resx" WithCulture="false" />
+  </ItemGroup>
 </Project>

DesktopClock/FormatEditor.xaml

@@ -1,15 +1,16 @@
 <UserControl x:Class="DesktopClock.FormatEditor"
              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
-             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:local="clr-namespace:DesktopClock">
     <StackPanel>
         <!-- One-click presets for common scenarios, each showing its live rendered output -->
-        <TextBlock Text="Common formats"
+        <TextBlock Text="{local:Loc CommonFormats}"
                    Style="{StaticResource EditorCaption}" />
         <WrapPanel x:Name="PresetsPanel"
                    Margin="0,0,0,10" />
 
         <!-- Free-form format with building blocks that insert tokens at the cursor -->
-        <TextBlock Text="Custom format"
+        <TextBlock Text="{local:Loc CustomFormat}"
                    Style="{StaticResource EditorCaption}" />
         <TextBox x:Name="FormatTextBox"
                  AcceptsReturn="True"
@@ -18,7 +19,7 @@
                  TextChanged="FormatTextBox_TextChanged" />
         <WrapPanel x:Name="TokensPanel"
                    Margin="0,0,0,10">
-            <TextBlock Text="Insert:"
+            <TextBlock Text="{local:Loc InsertToken}"
                        FontSize="12"
                        Foreground="{DynamicResource TextSecondaryBrush}"
                        VerticalAlignment="Center"
@@ -32,7 +33,7 @@
                 CornerRadius="{DynamicResource ControlCornerRadius}"
                 Padding="10,7">
             <StackPanel>
-                <TextBlock Text="Preview"
+                <TextBlock Text="{local:Loc Preview}"
                            FontSize="12"
                            Foreground="{DynamicResource TextSecondaryBrush}"
                            Margin="0,0,0,2" />