From 49ec9fbead9c6ba75763299abe540e73bac2804e Mon Sep 17 00:00:00 2001
From: TekH <h.tek@digitaldata.works>
Date: Wed, 1 Jul 2026 01:25:24 +0200
Subject: [PATCH] Add PdfSharp font resolver for .NET 8 compatibility

Added a `PdfSharpFontResolver` class to enable font resolution
for PdfSharp in .NET 8, addressing the lack of system font
access. The resolver reads fonts from the Windows Fonts folder
and supports the Arial font family. Registered the resolver
globally in `Program.cs` using `GlobalFontSettings.FontResolver`.

Updated `Program.cs` with comments explaining the necessity of
the resolver for .NET 8. The resolver includes methods to map
font family names to specific font files and load font data.
Throws a `FileNotFoundException` if required fonts are missing.

Made minor formatting changes in `Program.cs` without altering
the `SwaggerDoc` description functionality.
---
 .../EnvelopeGenerator.Server/Program.cs       |  6 ++-
 .../Services/PdfSharpFontResolver.cs          | 46 +++++++++++++++++++
 2 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 EnvelopeGenerator.Server/EnvelopeGenerator.Server/Services/PdfSharpFontResolver.cs

diff --git a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Program.cs b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Program.cs
index 96ba37ca..fbdb824c 100644
--- a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Program.cs
+++ b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Program.cs
@@ -104,7 +104,7 @@ try
         {
             Version = "v1",
             Title = "signFLOW Absender-API",
-            Description = "Eine API zur Verwaltung der Erstellung, des Versands und der Nachverfolgung von Umschlägen in der signFLOW-Anwendung.",
+            Description = "Eine API zur Verwaltung der Erstellung, des Versands und der Nachverfolgung von Umschl�gen in der signFLOW-Anwendung.",
             Contact = new OpenApiContact
             {
                 Name = "Digital Data GmbH",
@@ -338,6 +338,10 @@ try
     builder.Services.AddDevExpressBlazor();
     builder.Services.AddDevExpressServerSideBlazorPdfViewer();
 
+    // PdfSharp font resolver — required for .NET 8 (no system font access without it)
+    PdfSharp.Fonts.GlobalFontSettings.FontResolver =
+        EnvelopeGenerator.Server.Services.PdfSharpFontResolver.Instance;
+
     // Configuration Options
     builder.Services.Configure<EnvelopeGenerator.Server.Client.Options.ApiOptions>(
         builder.Configuration.GetSection("ApiOptions"));
diff --git a/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Services/PdfSharpFontResolver.cs b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Services/PdfSharpFontResolver.cs
new file mode 100644
index 00000000..84acfe22
--- /dev/null
+++ b/EnvelopeGenerator.Server/EnvelopeGenerator.Server/Services/PdfSharpFontResolver.cs
@@ -0,0 +1,46 @@
+using PdfSharp.Fonts;
+
+namespace EnvelopeGenerator.Server.Services;
+
+/// <summary>
+/// PdfSharp 6.x IFontResolver for .NET 8.
+/// PdfSharp cannot access system fonts on .NET Core/8 without an explicit resolver.
+/// This implementation reads fonts directly from the Windows Fonts folder.
+/// Register once at startup: GlobalFontSettings.FontResolver = PdfSharpFontResolver.Instance;
+/// </summary>
+public class PdfSharpFontResolver : IFontResolver
+{
+    public static readonly PdfSharpFontResolver Instance = new();
+
+    private static readonly string FontsFolder =
+        Environment.GetFolderPath(Environment.SpecialFolder.Fonts);
+
+    public FontResolverInfo? ResolveTypeface(string familyName, bool isBold, bool isItalic)
+    {
+        var key = familyName.ToLowerInvariant() switch
+        {
+            "arial" => isBold ? "arialbd" : "arial",
+            _       => null
+        };
+
+        return key is null ? null : new FontResolverInfo(key);
+    }
+
+    public byte[] GetFont(string faceName)
+    {
+        var fileName = faceName switch
+        {
+            "arialbd" => "arialbd.ttf",
+            _         => "arial.ttf",
+        };
+
+        var path = Path.Combine(FontsFolder, fileName);
+
+        if (!File.Exists(path))
+            throw new FileNotFoundException(
+                $"Font file not found: {path}. " +
+                "Ensure Arial is installed on the server.");
+
+        return File.ReadAllBytes(path);
+    }
+}