Fix processing of widget annotation if page is deleted

DEVSIX-5760

Author: Eugene Bochilo

kernel/src/main/java/com/itextpdf/kernel/pdf/PdfDocument.java

@@ -2277,18 +2277,25 @@ private void updateValueInMarkInfoDict(PdfName key, PdfObject value) {
     }
 
     /**
-     * This method removes all annotation entries from form fields associated with a given page.
+     * Removes all widgets associated with a given page from AcroForm structure. Widgets can be either pure or merged.
      *
      * @param page to remove from.
      */
     private void removeUnusedWidgetsFromFields(PdfPage page) {
         if (page.isFlushed()) {
             return;
         }
+
+        final PdfDictionary acroForm = this.getCatalog().getPdfObject().getAsDictionary(PdfName.AcroForm);
+        final PdfArray fields = acroForm == null ? null : acroForm.getAsArray(PdfName.Fields);
+
         List<PdfAnnotation> annots = page.getAnnotations();
         for (PdfAnnotation annot : annots) {
             if (annot.getSubtype().equals(PdfName.Widget)) {
                 ((PdfWidgetAnnotation) annot).releaseFormFieldFromWidgetAnnotation();
+                if (fields != null) {
+                    fields.remove(annot.getPdfObject());
+                }
             }
         }
     }

kernel/src/main/java/com/itextpdf/kernel/pdf/annot/PdfWidgetAnnotation.java

@@ -75,30 +75,6 @@ protected PdfWidgetAnnotation(PdfDictionary pdfObject) {
         super(pdfObject);
     }
 
-    private HashSet<PdfName> widgetEntries = new HashSet<PdfName>();
-
-    {
-        widgetEntries.add(PdfName.Subtype);
-        widgetEntries.add(PdfName.Type);
-        widgetEntries.add(PdfName.Rect);
-        widgetEntries.add(PdfName.Contents);
-        widgetEntries.add(PdfName.P);
-        widgetEntries.add(PdfName.NM);
-        widgetEntries.add(PdfName.M);
-        widgetEntries.add(PdfName.F);
-        widgetEntries.add(PdfName.AP);
-        widgetEntries.add(PdfName.AS);
-        widgetEntries.add(PdfName.Border);
-        widgetEntries.add(PdfName.C);
-        widgetEntries.add(PdfName.StructParent);
-        widgetEntries.add(PdfName.OC);
-        widgetEntries.add(PdfName.H);
-        widgetEntries.add(PdfName.MK);
-        widgetEntries.add(PdfName.A);
-        widgetEntries.add(PdfName.AA);
-        widgetEntries.add(PdfName.BS);
-    }
-
     @Override
     public PdfName getSubtype() {
         return PdfName.Widget;
@@ -133,22 +109,20 @@ public PdfName getHighlightMode() {
     }
 
     /**
-     * This method removes all widget annotation entries from the form field  the given annotation merged with.
+     * Remove widget annotation from AcroForm hierarchy.
      */
-    public void releaseFormFieldFromWidgetAnnotation(){
-        PdfDictionary annotDict = getPdfObject();
-        for (PdfName entry: widgetEntries) {
-            annotDict.remove(entry);
-        }
-        PdfDictionary parent = annotDict.getAsDictionary(PdfName.Parent);
-        if (parent != null && annotDict.size() == 1) {
+    public void releaseFormFieldFromWidgetAnnotation() {
+        PdfDictionary annotationDictionary = getPdfObject();
+        PdfDictionary parent = annotationDictionary.getAsDictionary(PdfName.Parent);
+        if (parent != null) {
             PdfArray kids = parent.getAsArray(PdfName.Kids);
-            kids.remove(annotDict);
-            if (kids.size() == 0) {
+            kids.remove(annotationDictionary);
+            if (kids.isEmpty()) {
                 parent.remove(PdfName.Kids);
             }
         }
     }
+
     /**
      * Set the visibility flags of the Widget annotation
      * Options are: HIDDEN, HIDDEN_BUT_PRINTABLE, VISIBLE, VISIBLE_BUT_DOES_NOT_PRINT

kernel/src/test/java/com/itextpdf/kernel/pdf/PdfDocumentTest.java

@@ -560,18 +560,37 @@ public void openDocumentWithInvalidCatalogVersionAndConservativeStrictnessReadin
     }
 
     @Test
-    // TODO DEVSIX-5760 cleaned widget left in the kids of the form field
     public void widgetDaEntryRemovePageTest() throws IOException, InterruptedException {
-        // In this test widgets contain entry /DA that is not specific for widget annotation, so after removing of the
-        // page such widget is not removed from the document. See method PdfDocument#removeUnusedWidgetsFromFields
-        // to see logic of removing unused widgets.
-        // If open the output PDF in Adobe Acrobat, widgets on pages 3-4 will not be viewed. It seems to adobe bug.
         final String testName = "widgetDaEntryRemovePage.pdf";
         final String outPdf = DESTINATION_FOLDER + testName;
-        PdfDocument pdfDocument = new PdfDocument(new PdfReader(SOURCE_FOLDER + "widgetWithDaEntry.pdf"),
-                new PdfWriter(outPdf));
-        pdfDocument.removePage(3);
-        pdfDocument.close();
+        try (PdfDocument pdfDocument = new PdfDocument(
+                new PdfReader(SOURCE_FOLDER + "widgetWithDaEntry.pdf"), new PdfWriter(outPdf))) {
+            pdfDocument.removePage(3);
+        }
+        Assert.assertNull(new CompareTool().compareByContent(outPdf, SOURCE_FOLDER + "cmp_" + testName,
+                DESTINATION_FOLDER));
+    }
+
+    @Test
+    public void mergedAndSimpleWidgetsRemovePageTest() throws IOException, InterruptedException {
+        final String testName = "mergedAndSimpleWidgetsRemovePage.pdf";
+        final String outPdf = DESTINATION_FOLDER + testName;
+        try (PdfDocument pdfDocument = new PdfDocument(
+                new PdfReader(SOURCE_FOLDER + "mergedAndSimpleWidgets.pdf"), new PdfWriter(outPdf))) {
+            pdfDocument.removePage(1);
+        }
+        Assert.assertNull(new CompareTool().compareByContent(outPdf, SOURCE_FOLDER + "cmp_" + testName,
+                DESTINATION_FOLDER));
+    }
+
+    @Test
+    public void mergedSiblingWidgetsRemovePageTest() throws IOException, InterruptedException {
+        final String testName = "mergedSiblingWidgetsRemovePage.pdf";
+        final String outPdf = DESTINATION_FOLDER + testName;
+        try (PdfDocument pdfDocument = new PdfDocument(
+                new PdfReader(SOURCE_FOLDER + "mergedSiblingWidgets.pdf"), new PdfWriter(outPdf))) {
+            pdfDocument.removePage(2);
+        }
         Assert.assertNull(new CompareTool().compareByContent(outPdf, SOURCE_FOLDER + "cmp_" + testName,
                 DESTINATION_FOLDER));
     }