feat: improve UI/UX of font loading

QuickLook.Plugin/QuickLook.Plugin.FontViewer/ObservableFileStream.cs

@@ -0,0 +1,26 @@
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace QuickLook.Plugin.FontViewer;
+
+public class ObservableFileStream(string path, FileMode mode, FileAccess access, FileShare share) : FileStream(path, mode, access, share)
+{
+    public bool IsEndOfStream { get; protected set; } = false;
+
+    public override int Read(byte[] array, int offset, int count)
+    {
+        int result = base.Read(array, offset, count);
+        if (result == 0)
+            IsEndOfStream = true;
+        return result;
+    }
+
+    public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+    {
+        int result = await base.ReadAsync(buffer, offset, count, cancellationToken);
+        if (result == 0)
+            IsEndOfStream = true;
+        return result;
+    }
+}