Mark positioning, script-aware GPOS/GSUB feature lookup, and ligature feature-tag support (#2503)

src/EPPlus.Export.Pdf.Tests/EPPlus.Export.Pdf.Tests.csproj

@@ -28,6 +28,9 @@
   </ItemGroup>
 
   <ItemGroup>
+    <None Update="Fonts\EBGaramond-Regular.ttf">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
     <None Update="Fonts\Roboto-Regular.ttf">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>

src/EPPlus.Export.Pdf.Tests/KerningReproTests.cs

@@ -18,7 +18,7 @@ Date               Author                       Change
 using System.IO;
 using System.Text;
 
-namespace EPPlusTest.PDF
+namespace EPPlus.Export.Pdf.Tests
 {
     /// <summary>
     /// Reproduces the reference sheet the kerning and mark-to-base work is measured against.

src/EPPlus.Export.Pdf.Tests/LigatureDligReproTests.cs

@@ -0,0 +1,126 @@
+/*************************************************************************************************
+  Required Notice: Copyright (C) EPPlus Software AB. 
+  This software is licensed under PolyForm Noncommercial License 1.0.0 
+  and may only be used for noncommercial purposes 
+  https://polyformproject.org/licenses/noncommercial/1.0.0/
+
+  A commercial license to use this software can be purchased at https://epplussoftware.com
+ *************************************************************************************************
+  Date               Author                       Change
+ *************************************************************************************************
+  09/07/2026         EPPlus Software AB           WP3/WP4 dlig ligature repro sheet
+ *************************************************************************************************/
+using EPPlus.Export.Pdf.Settings;
+using EPPlus.Export.Pdf.Tests;
+using EPPlus.Fonts.OpenType;
+using OfficeOpenXml;
+using OfficeOpenXml.Interfaces.Fonts;
+using OfficeOpenXml.Style;
+using System;
+using System.IO;
+
+namespace EPPlusTest.PDF
+{
+    /// <summary>
+    /// Visible before/after repro for the ligature feature-tag fix: EBGaramond's "dlig" feature
+    /// merges "Th" into a single connected historical ligature glyph - a real, visually obvious
+    /// effect, unlike "liga" which only covers the common ff/fi/fl set.
+    ///
+    /// Does not depend on a system font. EBGaramond-Regular.ttf is a repo test font (see
+    /// EPPlus.Fonts.OpenType.Tests/Fonts) and is loaded via workbook.ConfigureFonts pointing at
+    /// this test project's own Fonts folder, so both tests below are deterministic and CI-safe.
+    ///
+    /// The two tests are NOT symmetric in how they export, and that is unavoidable given the
+    /// current public API:
+    ///
+    ///   - "Off" uses PdfTestBase.SaveAsPdf(sheet, name), since the default GsubFeatures
+    ///     (Liga | Clig) is already what it needs.
+    ///   - "On" needs GsubFeature.Dlig, which cannot be reached through the plain SaveAsPdf
+    ///     overloads at all - ExcelWorksheet.SaveAsPdf always builds its own PdfPageSettings
+    ///     internally (GetPdfSettings.GetPdfSettingsFromPrinterSettings), with no path from
+    ///     ExcelPrinterSettings into GsubFeatures/GposFeatures. "On" therefore uses
+    ///     PdfTestBase's PdfPageSettings-accepting SaveAsPdf overload instead.
+    /// </summary>
+    [TestClass]
+    public class LigatureDligReproTests : PdfTestBase
+    {
+        private const string ReproFontFamily = "EB Garamond";
+        private const float ReproFontSize = 48f;
+        private const string ReproText = "Th";
+
+        private static string FontsFolder => Path.Combine(AppContext.BaseDirectory, "Fonts");
+
+        [TestMethod]
+        public void Th_EBGaramond48_DligOff_DoesNotLigate()
+        {
+            using (var package = OpenPackage("WP3DligRepro_Off.xlsx", true))
+            {
+                var workbook = package.Workbook;
+
+                workbook.ConfigureFonts(cfg =>
+                {
+                    cfg.FontDirectories.Add(FontsFolder);
+                    cfg.SearchSystemDirectories = false;
+                });
+
+                var sheet = BuildReproSheet(workbook);
+
+                // Default GsubFeatures is Liga | Clig - "dlig" is not requested, so this is the
+                // "before" state: "Th" renders as two separate glyphs.
+                SaveAsPdf(sheet, "WP3DligRepro_Off");
+
+                SaveWorkbook("WP3DligRepro_Off.xlsx", package);
+            }
+        }
+
+        [TestMethod]
+        public void Th_EBGaramond48_DligOn_MergesIntoLigature()
+        {
+            using (var engine = new OpenTypeFontEngine(cfg =>
+            {
+                cfg.FontDirectories.Add(FontsFolder);
+                cfg.SearchSystemDirectories = false;
+            }))
+            using (var package = OpenPackage("WP3DligRepro_On.xlsx", true))
+            {
+                var sheet = BuildReproSheet(package.Workbook);
+
+                // GsubFeature.Dlig cannot be requested through the plain SaveAsPdf overloads -
+                // see PdfTestBase's PdfPageSettings-accepting overload for why.
+                var settings = new PdfPageSettings(engine)
+                {
+                    GsubFeatures = GsubFeature.Liga | GsubFeature.Clig | GsubFeature.Dlig
+                };
+
+                SaveAsPdf(sheet, "WP3DligRepro_On", settings);
+
+                SaveWorkbook("WP3DligRepro_On.xlsx", package);
+            }
+        }
+
+        /// <summary>
+        /// Open WP3DligRepro_Off.pdf and WP3DligRepro_On.pdf side by side (both under
+        /// _pdfPath, i.e. c:\epplusTest\Testoutput\PDF\). In "Off", "Th" renders as a plain T
+        /// followed by a plain h. In "On" it renders as a single connected T-h glyph with a
+        /// joining stroke - visibly narrower than the two separate letters. Before the fix, both
+        /// files rendered identically, since "dlig" never reached the shaper regardless of what
+        /// GsubFeatures was set to.
+        /// </summary>
+        private static ExcelWorksheet BuildReproSheet(ExcelWorkbook workbook)
+        {
+            var sheet = workbook.Worksheets.Add("Dlig");
+
+            sheet.Cells["A1"].Value = ReproText;
+            sheet.Cells["A1"].Style.Font.Name = ReproFontFamily;
+            sheet.Cells["A1"].Style.Font.Size = ReproFontSize;
+            sheet.Cells["A1"].Style.HorizontalAlignment = ExcelHorizontalAlignment.Left;
+            sheet.Cells["A1"].Style.Indent = 0;
+
+            sheet.Column(1).Width = 25;
+            sheet.Row(1).CustomHeight = true;
+            sheet.Row(1).Height = 70;
+
+            return sheet;
+        }
+    }
+}