Improve Annotations

 # Changelog
 
+## 1.6.0
+
+- Improve Annotations
+
 ## 1.5.0
 
 - Fix Align debug painting

@@ -19,125 +19,138 @@
 part of pdf;
 
 class PdfAnnot extends PdfObject {
-  PdfAnnot._create(PdfPage pdfPage,
-      {String type,
-      this.content,
-      this.srcRect,
-      @required this.subtype,
-      this.dest,
-      this.destRect,
-      this.border,
-      this.url,
-      this.name})
-      : assert(subtype != null),
-        super(pdfPage.pdfDocument, type ?? '/Annot') {
+  PdfAnnot(this.pdfPage, this.annot)
+      : assert(annot != null),
+        super(pdfPage.pdfDocument, '/Annot') {
     pdfPage.annotations.add(this);
   }
 
-  /// Creates a text annotation
-  /// @param rect coordinates
-  /// @param s Text for this annotation
+  /// Create a text annotation
+  @deprecated
   factory PdfAnnot.text(
     PdfPage pdfPage, {
     @required PdfRect rect,
     @required String content,
     PdfBorder border,
   }) =>
-      PdfAnnot._create(
+      PdfAnnot(
           pdfPage,
-        subtype: '/Text',
-        srcRect: rect,
+          PdfAnnotText(
+            rect: rect,
             content: content,
             border: border,
-      );
-
-  /// Creates a link annotation
-  /// @param srcRect coordinates
-  /// @param dest Destination for this link. The page will fit the display.
-  /// @param destRect Rectangle describing what part of the page to be displayed
-  /// (must be in User Coordinates)
-  factory PdfAnnot.link(
-    PdfPage pdfPage, {
-    @required PdfRect srcRect,
-    @required PdfPage dest,
-    PdfRect destRect,
-    PdfBorder border,
-  }) =>
-      PdfAnnot._create(
-        pdfPage,
-        subtype: '/Link',
-        srcRect: srcRect,
-        dest: dest,
-        destRect: destRect,
-        border: border,
-      );
+          ));
 
   /// Creates an external link annotation
+  @deprecated
   factory PdfAnnot.urlLink(
     PdfPage pdfPage, {
     @required PdfRect rect,
     @required String dest,
     PdfBorder border,
   }) =>
-      PdfAnnot._create(
+      PdfAnnot(
           pdfPage,
-        subtype: '/Link',
-        srcRect: rect,
+          PdfAnnotUrlLink(
+            rect: rect,
             url: dest,
             border: border,
-      );
+          ));
 
   /// Creates a link annotation to a named destination
+  @deprecated
   factory PdfAnnot.namedLink(
     PdfPage pdfPage, {
     @required PdfRect rect,
     @required String dest,
     PdfBorder border,
   }) =>
-      PdfAnnot._create(
+      PdfAnnot(
         pdfPage,
-        subtype: '/Link',
-        srcRect: rect,
-        name: dest,
+        PdfAnnotNamedLink(
+          rect: rect,
+          dest: dest,
           border: border,
+        ),
       );
 
-  /// The subtype of the outline, ie text, note, etc
-  final String subtype;
+  /// The annotation content
+  final PdfAnnotBase annot;
 
-  /// The size of the annotation
-  final PdfRect srcRect;
+  /// The page where the annotation will display
+  final PdfPage pdfPage;
 
-  /// The text of a text annotation
-  final String content;
+  /// Output the annotation
+  ///
+  /// @param os OutputStream to send the object to
+  @override
+  void _prepare() {
+    super._prepare();
+    annot.build(pdfPage, params);
+  }
+}
 
-  /// Link to the Destination page
-  final PdfObject dest;
+enum PdfAnnotFlags {
+  invisible,
+  hidden,
+  print,
+  noZoom,
+  noRotate,
+  noView,
+  readOnly,
+  locked,
+  toggleNoView,
+  lockedContent
+}
 
-  /// If destRect is null then this is the region of the destination page shown.
-  /// Otherwise they are ignored.
-  final PdfRect destRect;
+abstract class PdfAnnotBase {
+  const PdfAnnotBase({
+    @required this.subtype,
+    @required this.rect,
+    this.border,
+    this.content,
+    this.name,
+    this.flags,
+    this.date,
+    this.color,
+  })  : assert(subtype != null),
+        assert(rect != null);
+
+  /// The subtype of the outline, ie text, note, etc
+  final String subtype;
+
+  final PdfRect rect;
 
   /// the border for this annotation
   final PdfBorder border;
 
-  /// The external url for a link
-  final String url;
+  /// The text of a text annotation
+  final String content;
 
   /// The internal name for a link
   final String name;
 
-  /// Output the annotation
-  ///
-  /// @param os OutputStream to send the object to
-  @override
-  void _prepare() {
-    super._prepare();
+  /// Flags specifying various characteristics of the annotation
+  final Set<PdfAnnotFlags> flags;
+
+  /// Last modification date
+  final DateTime date;
 
+  /// Color
+  final PdfColor color;
+
+  int get flagValue => flags
+      ?.map<int>((PdfAnnotFlags e) => 1 >> e.index)
+      ?.reduce((int a, int b) => a | b);
+
+  @protected
+  @mustCallSuper
+  void build(PdfPage page, Map<String, PdfStream> params) {
     params['/Subtype'] = PdfStream.string(subtype);
     params['/Rect'] = PdfStream()
-      ..putNumArray(
-          <double>[srcRect.left, srcRect.bottom, srcRect.right, srcRect.top]);
+      ..putNumArray(<double>[rect.left, rect.bottom, rect.right, rect.top]);
+
+    params['/P'] = page.ref();
 
     // handle the border
     if (border == null) {
@@ -146,39 +159,194 @@ class PdfAnnot extends PdfObject {
       params['/BS'] = border.ref();
     }
 
-    // Now the annotation subtypes
-    if (subtype == '/Text') {
+    if (content != null) {
       params['/Contents'] = PdfStream()..putLiteral(content);
-    } else if (subtype == '/Link') {
-      if (url != null) {
+    }
+
+    if (name != null) {
+      params['/NM'] = PdfStream()..putLiteral(name);
+    }
+
+    if (flags != null) {
+      params['/F'] = PdfStream.intNum(flagValue);
+    }
+
+    if (date != null) {
+      params['/M'] = PdfStream()..putDate(date);
+    }
+
+    if (color != null) {
+      if (color is PdfColorCmyk) {
+        final PdfColorCmyk k = color;
+        params['/C'] = PdfStream()
+          ..putNumList(<double>[k.cyan, k.magenta, k.yellow, k.black]);
+      } else {
+        params['/C'] = PdfStream()
+          ..putNumList(<double>[color.red, color.green, color.blue]);
+      }
+    }
+  }
+}
+
+class PdfAnnotText extends PdfAnnotBase {
+  /// Create a text annotation
+  const PdfAnnotText({
+    @required PdfRect rect,
+    @required String content,
+    PdfBorder border,
+    String name,
+    Set<PdfAnnotFlags> flags,
+    DateTime date,
+    PdfColor color,
+  }) : super(
+          subtype: '/Text',
+          rect: rect,
+          border: border,
+          content: content,
+          name: name,
+          flags: flags,
+          date: date,
+          color: color,
+        );
+}
+
+class PdfAnnotNamedLink extends PdfAnnotBase {
+  /// Create a named link annotation
+  const PdfAnnotNamedLink({
+    @required PdfRect rect,
+    @required this.dest,
+    PdfBorder border,
+    Set<PdfAnnotFlags> flags,
+    DateTime date,
+    PdfColor color,
+  }) : super(
+          subtype: '/Link',
+          rect: rect,
+          border: border,
+          flags: flags,
+          date: date,
+          color: color,
+        );
+
+  final String dest;
+
+  @override
+  void build(PdfPage page, Map<String, PdfStream> params) {
+    super.build(page, params);
+    params['/A'] = PdfStream()
+      ..putDictionary(
+        <String, PdfStream>{
+          '/S': PdfStream()..putString('/GoTo'),
+          '/D': PdfStream()..putText(dest),
+        },
+      );
+  }
+}
+
+class PdfAnnotUrlLink extends PdfAnnotBase {
+  /// Create an url link annotation
+  const PdfAnnotUrlLink({
+    @required PdfRect rect,
+    @required this.url,
+    PdfBorder border,
+    Set<PdfAnnotFlags> flags,
+    DateTime date,
+    PdfColor color,
+  }) : super(
+          subtype: '/Link',
+          rect: rect,
+          border: border,
+          flags: flags,
+          date: date,
+          color: color,
+        );
+
+  final String url;
+
+  @override
+  void build(PdfPage page, Map<String, PdfStream> params) {
+    super.build(page, params);
     params['/A'] = PdfStream()
-          ..putDictionary(<String, PdfStream>{
+      ..putDictionary(
+        <String, PdfStream>{
           '/S': PdfStream()..putString('/URI'),
           '/URI': PdfStream()..putText(url),
-          });
-      } else if (name != null) {
-        params['/A'] = PdfStream()
-          ..putDictionary(<String, PdfStream>{
-            '/S': PdfStream()..putString('/GoTo'),
-            '/D': PdfStream()..putText(name),
-          });
-      } else {
-        final List<PdfStream> dests = <PdfStream>[];
-        dests.add(dest.ref());
-        if (destRect == null) {
-          dests.add(PdfStream.string('/Fit'));
-        } else {
-          dests.add(PdfStream.string('/FitR '));
-          dests.add(PdfStream()
-            ..putNumList(<double>[
-              destRect.left,
-              destRect.bottom,
-              destRect.right,
-              destRect.top
-            ]));
+        },
+      );
   }
-        params['/Dest'] = PdfStream.array(dests);
+}
+
+enum PdfAnnotHighlighting { none, invert, outline, push, toggle }
+
+abstract class PdfAnnotWidget extends PdfAnnotBase {
+  /// Create an url link annotation
+  const PdfAnnotWidget(
+    PdfRect rect,
+    this.fieldType, {
+    this.fieldName,
+    PdfBorder border,
+    Set<PdfAnnotFlags> flags,
+    DateTime date,
+    PdfColor color,
+    this.highlighting,
+    this.value,
+  }) : super(
+          subtype: '/Widget',
+          rect: rect,
+          border: border,
+          flags: flags,
+          date: date,
+          color: color,
+        );
+
+  final String fieldType;
+
+  final String fieldName;
+
+  final PdfAnnotHighlighting highlighting;
+
+  final PdfStream value;
+
+  @override
+  void build(PdfPage page, Map<String, PdfStream> params) {
+    super.build(page, params);
+
+    params['/FT'] = PdfStream.string(fieldType);
+
+    if (fieldName != null) {
+      params['/T'] = PdfStream()..putLiteral(fieldName);
+    }
+
+    if (value != null) {
+      params['/V'] = value;
     }
   }
+}
+
+class PdfAnnotSign extends PdfAnnotWidget {
+  const PdfAnnotSign(
+    PdfRect rect, {
+    String fieldName,
+    PdfBorder border,
+    Set<PdfAnnotFlags> flags,
+    DateTime date,
+    PdfColor color,
+    PdfAnnotHighlighting highlighting,
+  }) : super(
+          rect,
+          '/Sig',
+          fieldName: fieldName,
+          border: border,
+          flags: flags,
+          date: date,
+          color: color,
+          highlighting: highlighting,
+        );
+
+  @override
+  void build(PdfPage page, Map<String, PdfStream> params) {
+    super.build(page, params);
+    assert(page.pdfDocument.sign != null);
+    params['/V'] = page.pdfDocument.sign.ref();
   }
 }

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+// ignore_for_file: omit_local_variable_types
+
 part of pdf;
 
 class PdfCatalog extends PdfObject {
@@ -67,8 +69,25 @@ class PdfCatalog extends PdfObject {
         PdfStream.string(PdfDocument._PdfPageModes[pageMode.index]);
 
     if (pdfDocument.sign != null) {
-      params['/Perms'] = PdfStream.dictionary(
-          <String, PdfStream>{'/DocMDP': pdfDocument.sign.ref()});
+      params['/Perms'] = PdfStream.dictionary(<String, PdfStream>{
+        '/DocMDP': pdfDocument.sign.ref(),
+      });
+    }
+
+    final List<PdfAnnot> widgets = <PdfAnnot>[];
+    for (PdfPage page in pdfDocument.pdfPageList.pages) {
+      for (PdfAnnot annot in page.annotations) {
+        if (annot.annot.subtype == '/Widget') {
+          widgets.add(annot);
+        }
+      }
+    }
+
+    if (widgets.isNotEmpty) {
+      params['/AcroForm'] = PdfStream.dictionary(<String, PdfStream>{
+        '/SigFlags': PdfStream.intNum(pdfDocument.sign?.flagsValue ?? 0),
+        '/Fields': PdfStream()..putObjectArray(widgets),
+      });
     }
   }
 }

@@ -15,6 +15,7 @@
  */
 
 // ignore_for_file: omit_local_variable_types
+// ignore_for_file: avoid_unused_constructor_parameters
 
 part of pdf;
 
@@ -33,13 +34,7 @@ class PDFAnnot extends PdfAnnot {
       double fb,
       double fr,
       double ft})
-      : super._create(pdfPage,
-            type: type,
-            content: s,
-            srcRect: PdfRect.fromLTRB(l, t, r, b),
-            subtype: subtype,
-            dest: dest,
-            destRect: PdfRect.fromLTRB(fl, ft, fr, fb));
+      : super(pdfPage, PdfAnnotText(rect: PdfRect(l, b, r, t), content: s));
 
   factory PDFAnnot.annotation(
           PdfPage pdfPage, String s, double l, double b, double r, double t) =>
@@ -342,12 +337,11 @@ class PDFPage extends PdfPage {
       double vh = PDFAnnot.FULL_PAGE]) {
     final PdfPoint xy1 = cxy(x, y + h);
     final PdfPoint xy2 = cxy(x + w, y);
-    final PdfPoint xy3 = cxy(vx, vy + vh);
-    final PdfPoint xy4 = cxy(vx + vw, vy);
-    final PdfAnnot ob = PdfAnnot.link(this,
-        srcRect: PdfRect.fromLTRB(xy1.x, xy1.y, xy2.x, xy2.y),
-        dest: dest,
-        destRect: PdfRect.fromLTRB(xy3.x, xy3.y, xy4.x, xy4.y));
+    final PdfAnnot ob = PdfAnnot.urlLink(
+      this,
+      rect: PdfRect.fromLTRB(xy1.x, xy1.y, xy2.x, xy2.y),
+      dest: 'https://github.com/DavBfr/dart_pdf',
+    );
     return ob;
   }
 

@@ -107,7 +107,7 @@ class PdfPage extends PdfObject {
     // the /Contents pages object
     if (contents.isNotEmpty) {
       if (contents.length == 1) {
-        params['/Contents'] = contents[0].ref();
+        params['/Contents'] = contents.first.ref();
       } else {
         params['/Contents'] = PdfStream()..putObjectArray(contents);
       }

@@ -18,29 +18,33 @@
 
 part of pdf;
 
-@immutable
-class PdfSignatureRange {
-  const PdfSignatureRange(this.start, this.end);
+enum PdfSigFlags { signaturesExist, appendOnly }
 
-  final int start;
-  final int end;
-}
+class PdfSignature extends PdfObject {
+  PdfSignature(
+    PdfDocument pdfDocument, {
+    @required this.crypto,
+    Set<PdfSigFlags> flags,
+  })  : assert(crypto != null),
+        flags = flags ?? const <PdfSigFlags>{PdfSigFlags.signaturesExist},
+        super(pdfDocument, '/Sig');
 
-abstract class PdfSignature extends PdfObject {
-  PdfSignature(PdfDocument pdfDocument) : super(pdfDocument, '/Sig');
+  final Set<PdfSigFlags> flags;
 
-  int _offsetStart;
-  int _offsetEnd;
+  final PdfSignatureBase crypto;
 
-  void preSign();
+  int get flagsValue => flags
+      .map<int>((PdfSigFlags e) => 1 >> e.index)
+      .reduce((int a, int b) => a | b);
 
-  void sign(PdfStream os, List<PdfSignatureRange> ranges);
+  int _offsetStart;
+  int _offsetEnd;
 
   @override
   void _write(PdfStream os) {
-    preSign();
+    crypto.preSign(params);
 
-    _offsetStart = os.offset;
+    _offsetStart = os.offset + '$objser $objgen obj\n'.length;
     super._write(os);
     _offsetEnd = os.offset;
   }
@@ -49,16 +53,13 @@ abstract class PdfSignature extends PdfObject {
     assert(_offsetStart != null && _offsetEnd != null,
         'Must reserve the object space before signing the document');
 
-    final List<PdfSignatureRange> ranges = <PdfSignatureRange>[
-      PdfSignatureRange(0, _offsetStart),
-      PdfSignatureRange(_offsetEnd, os.offset),
-    ];
+    crypto.sign(os, params, _offsetStart, _offsetEnd);
+  }
+}
 
-    sign(os, ranges);
-    final PdfStream signature = PdfStream();
-    super._write(signature);
+abstract class PdfSignatureBase {
+  void preSign(Map<String, PdfStream> params);
 
-    assert(signature.offset == _offsetEnd - _offsetStart);
-    os.output().replaceRange(_offsetStart, _offsetEnd, signature.output());
-  }
+  void sign(PdfStream os, Map<String, PdfStream> params, int offsetStart,
+      int offsetEnd);
 }

@@ -39,7 +39,7 @@ class Anchor extends SingleChildWidget {
     if (description != null) {
       final Vector3 rb = mat.transform3(Vector3(box.right, box.top, 0));
       final PdfRect ibox = PdfRect.fromLTRB(lt.x, lt.y, rb.x, rb.y);
-      PdfAnnot.text(context.page, content: description, rect: ibox);
+      PdfAnnot(context.page, PdfAnnotText(rect: ibox, content: description));
     }
   }
 }
@@ -62,10 +62,12 @@ class AnnotationLink extends AnnotationBuilder {
 
   @override
   void build(Context context, PdfRect box) {
-    PdfAnnot.namedLink(
+    PdfAnnot(
       context.page,
+      PdfAnnotNamedLink(
         rect: localToGlobal(context, box),
         dest: destination,
+      ),
     );
   }
 }
@@ -77,10 +79,63 @@ class AnnotationUrl extends AnnotationBuilder {
 
   @override
   void build(Context context, PdfRect box) {
-    PdfAnnot.urlLink(
+    PdfAnnot(
       context.page,
+      PdfAnnotUrlLink(
         rect: localToGlobal(context, box),
-      dest: destination,
+        url: destination,
+      ),
+    );
+  }
+}
+
+class AnnotationSignature extends AnnotationBuilder {
+  AnnotationSignature(
+    this.crypto, {
+    this.name,
+    this.signFlags,
+    this.border,
+    this.flags,
+    this.date,
+    this.color,
+    this.highlighting,
+  }) : assert(crypto != null);
+
+  final Set<PdfSigFlags> signFlags;
+
+  final PdfSignatureBase crypto;
+
+  final String name;
+
+  final PdfBorder border;
+
+  final Set<PdfAnnotFlags> flags;
+
+  final DateTime date;
+
+  final PdfColor color;
+
+  final PdfAnnotHighlighting highlighting;
+
+  @override
+  void build(Context context, PdfRect box) {
+    context.document.sign ??= PdfSignature(
+      context.document,
+      crypto: crypto,
+      flags: signFlags,
+    );
+
+    PdfAnnot(
+      context.page,
+      PdfAnnotSign(
+        localToGlobal(context, box),
+        fieldName: name,
+        border: border,
+        flags: flags,
+        date: date,
+        color: color,
+        highlighting: highlighting,
+      ),
     );
   }
 }
@@ -117,3 +172,30 @@ class UrlLink extends Annotation {
       : assert(child != null),
         super(child: child, builder: AnnotationUrl(destination));
 }
+
+class Signature extends Annotation {
+  Signature({
+    @required Widget child,
+    @required PdfSignatureBase crypto,
+    @required String name,
+    Set<PdfSigFlags> signFlags,
+    PdfBorder border,
+    Set<PdfAnnotFlags> flags,
+    DateTime date,
+    PdfColor color,
+    PdfAnnotHighlighting highlighting,
+  })  : assert(child != null),
+        assert(crypto != null),
+        super(
+            child: child,
+            builder: AnnotationSignature(
+              crypto,
+              signFlags: signFlags,
+              name: name,
+              border: border,
+              flags: flags,
+              date: date,
+              color: color,
+              highlighting: highlighting,
+            ));
+}

@@ -4,7 +4,7 @@ description: A pdf producer for Dart. It can create pdf files for both web or fl
 homepage: https://github.com/DavBfr/dart_pdf/tree/master/pdf
 repository: https://github.com/DavBfr/dart_pdf
 issue_tracker: https://github.com/DavBfr/dart_pdf/issues
-version: 1.5.0
+version: 1.6.0
 
 environment:
   sdk: ">=2.3.0 <3.0.0"

@@ -29,18 +29,35 @@ void main() {
     final PdfPage page1 =
         PdfPage(pdf, pageFormat: const PdfPageFormat(500, 300));
 
+    pdf.pdfNames.addDest('target', page1, posY: 100);
+
     final PdfGraphics g = page.getGraphics();
 
-    PdfAnnot.text(page,
-        content: 'Hello', rect: const PdfRect(100, 100, 50, 50));
+    PdfAnnot(
+      page,
+      const PdfAnnotText(
+        rect: PdfRect(100, 100, 50, 50),
+        content: 'Hello',
+      ),
+    );
 
-    PdfAnnot.link(page, dest: page1, srcRect: const PdfRect(100, 150, 50, 50));
+    PdfAnnot(
+      page,
+      const PdfAnnotNamedLink(
+        dest: 'target',
+        rect: PdfRect(100, 150, 50, 50),
+      ),
+    );
     g.drawRect(100, 150, 50, 50);
     g.strokePath();
 
-    PdfAnnot.urlLink(page,
-        rect: const PdfRect(100, 250, 50, 50),
-        dest: 'https://github.com/DavBfr/dart_pdf/');
+    PdfAnnot(
+      page,
+      const PdfAnnotUrlLink(
+        rect: PdfRect(100, 250, 50, 50),
+        url: 'https://github.com/DavBfr/dart_pdf/',
+      ),
+    );
     g.drawRect(100, 250, 50, 50);
     g.strokePath();