ENH: Allow setting form field flags (#802)

Closes #574
Closes #801

Co-authored-by: Craig Jones <craig@k6nnl.com>

PyPDF2/pdf.py

@@ -371,7 +371,7 @@ def appendPagesFromReader(self, reader, after_page_append=None):
             # Trigger callback, pass writer page as parameter
             if callable(after_page_append): after_page_append(writer_page)
 
-    def updatePageFormFieldValues(self, page, fields):
+    def updatePageFormFieldValues(self, page, fields, flags=0):
         '''
         Update the form field values for a given page from a fields dictionary.
         Copy field texts and values from fields to page.
@@ -381,6 +381,9 @@ def updatePageFormFieldValues(self, page, fields):
             and field data will be updated.
         :param fields: a Python dictionary of field names (/T) and text
             values (/V)
+        :param flags: An integer (0 to 7). The first bit sets ReadOnly, the
+            second bit sets Required, the third bit sets NoExport. See
+            PDF Reference Table 8.70 for details.
         '''
         # Iterate through pages, update field values
         for j in range(0, len(page[PG.ANNOTS])):
@@ -394,6 +397,8 @@ def updatePageFormFieldValues(self, page, fields):
                     writer_annot.update({
                         NameObject("/V"): TextStringObject(fields[field])
                     })
+                    if flags:
+                        writer_annot.update({NameObject("/Ff"): NumberObject(flags)})
                 elif writer_parent_annot.get('/T') == field:
                     writer_parent_annot.update({
                         NameObject("/V"): TextStringObject(fields[field])

Tests/test_writer.py

@@ -166,7 +166,7 @@ def test_fill_form():
 
     writer.addPage(page)
 
-    writer.updatePageFormFieldValues(writer.getPage(0), {"foo": "some filled in text"})
+    writer.updatePageFormFieldValues(writer.getPage(0), {"foo": "some filled in text"}, flags=1)
 
     # write "output" to PyPDF2-output.pdf
     tmp_filename = "dont_commit_filled_pdf.pdf"