Fallback fonts on macos

StabilityMatrix.Avalonia/App.axaml.cs

@@ -17,11 +17,13 @@ using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Data.Core.Plugins;
 using Avalonia.Input.Platform;
 using Avalonia.Markup.Xaml;
+using Avalonia.Media;
 using Avalonia.Media.Imaging;
 using Avalonia.Platform;
 using Avalonia.Platform.Storage;
 using Avalonia.Styling;
 using Avalonia.Threading;
+using FluentAvalonia.Interop;
 using FluentAvalonia.UI.Controls;
 using MessagePipe;
 using Microsoft.Extensions.Configuration;
@@ -97,6 +99,8 @@ public sealed class App : Application
     public IClassicDesktopStyleApplicationLifetime? DesktopLifetime =>
         ApplicationLifetime as IClassicDesktopStyleApplicationLifetime;
 
+    public static new App? Current => (App?)Application.Current;
+
     /// <summary>
     /// Called before <see cref="Services"/> is built.
     /// Can be used by UI tests to override services.
@@ -107,6 +111,8 @@ public sealed class App : Application
     {
         AvaloniaXamlLoader.Load(this);
 
+        SetFontFamily(GetPlatformDefaultFontFamily());
+
         // Set design theme
         if (Design.IsDesignMode)
         {
@@ -182,6 +188,58 @@ public sealed class App : Application
         }
     }
 
+    /// <summary>
+    /// Set the default font family for the application.
+    /// </summary>
+    private void SetFontFamily(FontFamily fontFamily)
+    {
+        Resources["ContentControlThemeFontFamily"] = fontFamily;
+    }
+
+    /// <summary>
+    /// Get the default font family for the current platform and language.
+    /// </summary>
+    public FontFamily GetPlatformDefaultFontFamily()
+    {
+        try
+        {
+            var fonts = new List<string>();
+
+            if (Cultures.Current?.Name == "ja-JP")
+            {
+                return Resources["NotoSansJP"] as FontFamily
+                    ?? throw new ApplicationException("Font NotoSansJP not found");
+            }
+
+            if (Compat.IsWindows)
+            {
+                fonts.Add(OSVersionHelper.IsWindows11() ? "Segoe UI Variable Text" : "Segoe UI");
+            }
+            else if (Compat.IsMacOS)
+            {
+                // Use Segoe fonts if installed, but we can't distribute them
+                fonts.Add("Segoe UI Variable");
+                fonts.Add("Segoe UI");
+
+                fonts.Add("San Francisco");
+                fonts.Add("Helvetica Neue");
+                fonts.Add("Helvetica");
+            }
+            else
+            {
+                return FontFamily.Default;
+            }
+
+            return new FontFamily(string.Join(",", fonts));
+        }
+        catch (Exception e)
+        {
+            LogManager.GetCurrentClassLogger().Error(e);
+
+            return FontFamily.Default;
+        }
+    }
+
     /// <summary>
     /// Setup tasks to be run shortly before any window is shown
     /// </summary>
@@ -220,8 +278,6 @@ public sealed class App : Application
             mainWindow.WindowStartupLocation = WindowStartupLocation.CenterScreen;
         }
 
-        mainWindow.SetDefaultFonts();
-
         VisualRoot = mainWindow;
         StorageProvider = mainWindow.StorageProvider;
         Clipboard = mainWindow.Clipboard ?? throw new NullReferenceException("Clipboard is null");

StabilityMatrix.Avalonia/Views/MainWindow.axaml.cs

@@ -91,6 +91,8 @@ public partial class MainWindow : AppWindowBase
         EventManager.Instance.CultureChanged += (_, _) => SetDefaultFonts();
         EventManager.Instance.UpdateAvailable += OnUpdateAvailable;
 
+        SetDefaultFonts();
+
         Observable
             .FromEventPattern<SizeChangedEventArgs>(this, nameof(SizeChanged))
             .Where(x => x.EventArgs.PreviousSize != x.EventArgs.NewSize)
@@ -243,54 +245,11 @@ public partial class MainWindow : AppWindowBase
         });
     }
 
-    public void SetDefaultFonts()
+    private void SetDefaultFonts()
     {
-        var fonts = new List<string>();
+        if (App.Current is not null)
-
-        try
-        {
-            if (Cultures.Current?.Name == "ja-JP")
-            {
-                var customFont = (Application.Current!.Resources["NotoSansJP"] as FontFamily)!;
-                Resources["ContentControlThemeFontFamily"] = customFont;
-                FontFamily = customFont;
-                return;
-            }
-
-            if (Compat.IsWindows)
-            {
-                if (OSVersionHelper.IsWindows11())
-                {
-                    fonts.Add("Segoe UI Variable Text");
-                }
-                else
-                {
-                    fonts.Add("Segoe UI");
-                }
-            }
-            else if (Compat.IsMacOS)
-            {
-                fonts.Add("San Francisco");
-                fonts.Add("Helvetica Neue");
-                fonts.Add("Helvetica");
-            }
-            else
-            {
-                Resources["ContentControlThemeFontFamily"] = FontFamily.Default;
-                FontFamily = FontFamily.Default;
-                return;
-            }
-
-            var fontString = new FontFamily(string.Join(",", fonts));
-            Resources["ContentControlThemeFontFamily"] = fontString;
-            FontFamily = fontString;
-        }
-        catch (Exception e)
         {
-            LogManager.GetCurrentClassLogger().Error(e);
+            FontFamily = App.Current.GetPlatformDefaultFontFamily();
-
-            Resources["ContentControlThemeFontFamily"] = FontFamily.Default;
-            FontFamily = FontFamily.Default;
         }
     }