Add more parameters to PdfObject

@@ -5,6 +5,7 @@
 - A borderRadius can only be given for a uniform Border
 - Add LayoutWidgetBuilder
 - Add GridPaper widget
+- Improve internal sructure
 
 ## 1.13.0
 

@@ -33,7 +33,7 @@ import 'stream.dart';
 class PdfAnnot extends PdfObject {
   PdfAnnot(this.pdfPage, this.annot)
       : assert(annot != null),
-        super(pdfPage.pdfDocument, '/Annot') {
+        super(pdfPage.pdfDocument, type: '/Annot') {
     pdfPage.annotations.add(this);
   }
 

@@ -33,7 +33,7 @@ class PdfCatalog extends PdfObject {
   )   : assert(pdfPageList != null),
         assert(pageMode != null),
         assert(names != null),
-        super(pdfDocument, '/Catalog');
+        super(pdfDocument, type: '/Catalog');
 
   /// The pages of the document
   final PdfPageList pdfPageList;

@@ -22,7 +22,7 @@ import 'object.dart';
 /// Encryption object
 abstract class PdfEncryption extends PdfObject {
   /// Creates an encryption object
-  PdfEncryption(PdfDocument pdfDocument) : super(pdfDocument, null);
+  PdfEncryption(PdfDocument pdfDocument) : super(pdfDocument);
 
   /// Encrypt some data
   Uint8List encrypt(Uint8List input, PdfObject object);

@@ -34,7 +34,7 @@ abstract class PdfFont extends PdfObject {
   /// font name to that in Pdf, defaulting to Helvetica if not possible.
   PdfFont.create(PdfDocument pdfDocument, {@required this.subtype})
       : assert(subtype != null),
-        super(pdfDocument, '/Font') {
+        super(pdfDocument, type: '/Font') {
     pdfDocument.fonts.add(this);
   }
 

@@ -27,7 +27,7 @@ class PdfFontDescriptor extends PdfObject {
     this.file,
   )   : assert(ttfFont != null),
         assert(file != null),
-        super(ttfFont.pdfDocument, '/FontDescriptor');
+        super(ttfFont.pdfDocument, type: '/FontDescriptor');
 
   /// File data
   final PdfObjectStream file;

@@ -28,7 +28,7 @@ class PdfInfo extends PdfObject {
       this.subject,
       this.keywords,
       this.producer})
-      : super(pdfDocument, null) {
+      : super(pdfDocument) {
     if (author != null) {
       params['/Author'] = PdfSecString.fromString(this, author);
     }

@@ -25,10 +25,12 @@ class PdfObject {
   /// This is usually called by extensors to this class, and sets the
   /// Pdf Object Type
   PdfObject(
-    this.pdfDocument, [
+    this.pdfDocument, {
     String type,
-  ])  : assert(pdfDocument != null),
-        objser = pdfDocument.genSerial() {
+    this.objgen = 0,
+    int objser,
+  })  : assert(pdfDocument != null),
+        objser = objser ?? pdfDocument.genSerial() {
     if (type != null) {
       params['/Type'] = PdfName(type);
     }
@@ -43,7 +45,7 @@ class PdfObject {
   final int objser;
 
   /// This is the generation number for this object.
-  final int objgen = 0;
+  final int objgen;
 
   /// This allows any Pdf object to refer to the document being constructed.
   final PdfDocument pdfDocument;

@@ -29,7 +29,7 @@ class PdfObjectStream extends PdfObject {
     PdfDocument pdfDocument, {
     String type,
     this.isBinary = false,
-  }) : super(pdfDocument, type);
+  }) : super(pdfDocument, type: type);
 
   /// This holds the stream's content.
   final PdfStream buf = PdfStream();

@@ -28,7 +28,7 @@ class PdfPage extends PdfObject with PdfGraphicStream {
   /// This constructs a Page object, which will hold any contents for this
   /// page.
   PdfPage(PdfDocument pdfDocument, {this.pageFormat = PdfPageFormat.standard})
-      : super(pdfDocument, '/Page') {
+      : super(pdfDocument, type: '/Page') {
     pdfDocument.pdfPageList.pages.add(this);
   }
 

@@ -22,7 +22,7 @@ import 'page.dart';
 /// PdfPageList object
 class PdfPageList extends PdfObject {
   /// This constructs a [PdfPageList] object.
-  PdfPageList(PdfDocument pdfDocument) : super(pdfDocument, '/Pages');
+  PdfPageList(PdfDocument pdfDocument) : super(pdfDocument, type: '/Pages');
 
   /// This holds the pages
   final List<PdfPage> pages = <PdfPage>[];

@@ -30,7 +30,7 @@ class PdfSignature extends PdfObject {
     Set<PdfSigFlags> flags,
   })  : assert(crypto != null),
         flags = flags ?? const <PdfSigFlags>{PdfSigFlags.signaturesExist},
-        super(pdfDocument, '/Sig');
+        super(pdfDocument, type: '/Sig');
 
   final Set<PdfSigFlags> flags;