From b33ad302bea729dfce68c9abf201de2084ba62cb Mon Sep 17 00:00:00 2001
From: Adrian-George Bostan <adrg@epistack.com>
Date: Thu, 21 Feb 2019 20:24:06 +0200
Subject: [PATCH] Add default values for the signature field

---
 pdf/model/appender.go | 5 +++++
 pdf/model/fields.go   | 1 +
 2 files changed, 6 insertions(+)

diff --git a/pdf/model/appender.go b/pdf/model/appender.go
index 2ec60621..0d2412af 100644
--- a/pdf/model/appender.go
+++ b/pdf/model/appender.go
@@ -405,6 +405,10 @@ func (a *PdfAppender) Sign(pageNum int, field *PdfFieldSignature) error {
 
 	// Add signature field annotations to the page annotations.
 	field.P = page.ToPdfObject()
+	if field.T == nil || field.T.String() == "" {
+		field.T = core.MakeString(fmt.Sprintf("Signature %d", page))
+	}
+
 	page.Annotations = append(page.Annotations, field.PdfAnnotationWidget.PdfAnnotation)
 
 	// Add signature field to the form.
@@ -412,6 +416,7 @@ func (a *PdfAppender) Sign(pageNum int, field *PdfFieldSignature) error {
 	if acroForm == nil {
 		acroForm = NewPdfAcroForm()
 	}
+	acroForm.SigFlags = core.MakeInteger(3)
 
 	fields := append(acroForm.AllFields(), field.PdfField)
 	acroForm.Fields = &fields
diff --git a/pdf/model/fields.go b/pdf/model/fields.go
index 69f0cebb..1f23e564 100644
--- a/pdf/model/fields.go
+++ b/pdf/model/fields.go
@@ -451,6 +451,7 @@ func NewPdfFieldSignature(signature *PdfSignature) *PdfFieldSignature {
 	field.PdfAnnotationWidget.container = field.PdfField.container
 
 	field.T = core.MakeString("")
+	field.F = core.MakeInteger(132)
 	field.V = signature
 	return field
 }