support looking up in reply to value for annotation #362

src/UglyToad.PdfPig.Tests/Integration/AnnotationReplyToTests.cs

@@ -0,0 +1,43 @@
+namespace UglyToad.PdfPig.Tests.Integration;
+
+using Annotations;
+using System.Linq;
+using Xunit;
+
+public class AnnotationReplyToTests
+{
+    private static string GetFilename()
+    {
+        return IntegrationHelpers.GetDocumentPath("annotation-comments.pdf");
+    }
+
+    [Fact]
+    public void HasCorrectNumberOfAnnotations()
+    {
+        using var document = PdfDocument.Open(GetFilename());
+
+        var page = document.GetPage(1);
+
+        var annotations = page.ExperimentalAccess.GetAnnotations().ToList();
+
+        Assert.Equal(4, annotations.Count);
+
+        Assert.Equal(AnnotationType.Text, annotations[0].Type);
+        Assert.Equal(AnnotationType.Popup, annotations[1].Type);
+        Assert.Equal(AnnotationType.Text, annotations[2].Type);
+        Assert.Equal(AnnotationType.Popup, annotations[3].Type);
+    }
+
+    [Fact]
+    public void SecondTextReplyToFirst()
+    {
+        using var document = PdfDocument.Open(GetFilename());
+
+        var page = document.GetPage(1);
+
+        var annotations = page.ExperimentalAccess.GetAnnotations().ToList();
+
+        Assert.Equal(annotations[0], annotations[2].InReplyTo);
+    }
+
+}

src/UglyToad.PdfPig.Tokens/NameToken.Constants.cs

@@ -290,6 +290,7 @@
         public static readonly NameToken Inklist = new NameToken("InkList");
         public static readonly NameToken Intent = new NameToken("Intent");
         public static readonly NameToken Interpolate = new NameToken("Interpolate");
+        public static readonly NameToken Irt = new NameToken("IRT");
         public static readonly NameToken It = new NameToken("IT");
         public static readonly NameToken ItalicAngle = new NameToken("ItalicAngle");
         // J

src/UglyToad.PdfPig/Annotations/Annotation.cs

@@ -88,15 +88,30 @@
         /// </summary>
         public bool HasDownAppearance => downAppearanceStream != null;
 
+        /// <summary>
+        /// The <see cref="Annotation"/> this annotation was in reply to. Can be <see langword="null" />
+        /// </summary>
+        public Annotation InReplyTo { get; }
+
         /// <summary>
         /// Create a new <see cref="Annotation"/>.
         /// </summary>
-        public Annotation(DictionaryToken annotationDictionary, AnnotationType type, PdfRectangle rectangle,
-            string content, string name, string modifiedDate,
-            AnnotationFlags flags, AnnotationBorder border, IReadOnlyList<QuadPointsQuadrilateral> quadPoints,
+        public Annotation(
+            DictionaryToken annotationDictionary,
+            AnnotationType type,
+            PdfRectangle rectangle,
+            string content,
+            string name,
+            string modifiedDate,
+            AnnotationFlags flags,
+            AnnotationBorder border,
+            IReadOnlyList<QuadPointsQuadrilateral> quadPoints,
             PdfAction action,
-            AppearanceStream normalAppearanceStream, AppearanceStream rollOverAppearanceStream,
-            AppearanceStream downAppearanceStream, string appearanceState)
+            AppearanceStream normalAppearanceStream,
+            AppearanceStream rollOverAppearanceStream,
+            AppearanceStream downAppearanceStream,
+            string appearanceState,
+            Annotation inReplyTo)
         {
             AnnotationDictionary = annotationDictionary ?? throw new ArgumentNullException(nameof(annotationDictionary));
             Type = type;
@@ -112,6 +127,7 @@
             this.rollOverAppearanceStream = rollOverAppearanceStream;
             this.downAppearanceStream = downAppearanceStream;
             this.appearanceState = appearanceState;
+            InReplyTo = inReplyTo;
         }
 
         /// <inheritdoc />

src/UglyToad.PdfPig/Annotations/AnnotationProvider.cs

@@ -33,6 +33,8 @@
 
         public IEnumerable<Annotation> GetAnnotations()
         {
+            var lookupAnnotations = new Dictionary<IndirectReference, Annotation>();
+
             if (!pageDictionary.TryGet(NameToken.Annots, tokenScanner, out ArrayToken annotationsArray))
             {
                 yield break;
@@ -45,6 +47,13 @@
                         continue;
                 }
 
+                Annotation replyTo = null;
+                if (annotationDictionary.TryGet(NameToken.Irt, out IndirectReferenceToken referencedAnnotation)
+                    && lookupAnnotations.TryGetValue(referencedAnnotation.Data, out var linkedAnnotation))
+                {
+                    replyTo = linkedAnnotation;
+                }
+
                 var type = annotationDictionary.Get<NameToken>(NameToken.Subtype, tokenScanner);
                 var annotationType = type.ToAnnotationType();
                 var action = GetAction(annotationDictionary);
@@ -136,9 +145,29 @@
                     appearanceState = appearanceStateToken.Data;
                 }
 
-                yield return new Annotation(annotationDictionary, annotationType, rectangle, 
-                    contents, name, modifiedDate, flags, border, quadPointRectangles, action,
-                    normalAppearanceStream, rollOverAppearanceStream, downAppearanceStream, appearanceState);
+                var annotation = new Annotation(
+                    annotationDictionary,
+                    annotationType,
+                    rectangle, 
+                    contents,
+                    name,
+                    modifiedDate,
+                    flags,
+                    border,
+                    quadPointRectangles,
+                    action,
+                    normalAppearanceStream,
+                    rollOverAppearanceStream,
+                    downAppearanceStream,
+                    appearanceState,
+                    replyTo);
+
+                if (token is IndirectReferenceToken indirectReference)
+                {
+                    lookupAnnotations[indirectReference.Data] = annotation;
+                }
+
+                yield return annotation;
             }
         }