Add debugging information

@@ -8,6 +8,7 @@
 - Implement fallback font
 - Implement Emoji support
 - Improve outlines containing non-sequential level increments [Roel Spilker]
+- Add debugging information
 
 ## 3.6.5
 

@@ -16,6 +16,7 @@
 
 import 'dart:collection';
 import 'dart:convert';
+import 'dart:math' as math;
 import 'dart:typed_data';
 
 import 'package:meta/meta.dart';
@@ -25,10 +26,12 @@ import 'color.dart';
 import 'obj/object.dart';
 import 'stream.dart';
 
+const _kIndentSize = 2;
+
 abstract class PdfDataType {
   const PdfDataType();
 
-  void output(PdfStream s);
+  void output(PdfStream s, [int? indent]);
 
   PdfStream _toStream() {
     final s = PdfStream();
@@ -53,7 +56,7 @@ class PdfBool extends PdfDataType {
   final bool value;
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     s.putString(value ? 'true' : 'false');
   }
 
@@ -81,7 +84,7 @@ class PdfNum extends PdfDataType {
   final num value;
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     if (value is int) {
       s.putString(value.toInt().toString());
     } else {
@@ -119,12 +122,12 @@ class PdfNumList extends PdfDataType {
   final List<num> values;
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     for (var n = 0; n < values.length; n++) {
       if (n > 0) {
         s.putByte(0x20);
       }
-      PdfNum(values[n]).output(s);
+      PdfNum(values[n]).output(s, indent);
     }
   }
 
@@ -289,7 +292,7 @@ class PdfString extends PdfDataType {
   }
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     _output(s, value);
   }
 
@@ -346,9 +349,9 @@ class PdfSecString extends PdfString {
   final PdfObject object;
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     if (object.pdfDocument.encryption == null) {
-      return super.output(s);
+      return super.output(s, indent);
     }
 
     final enc = object.pdfDocument.encryption!.encrypt(value, object);
@@ -362,7 +365,7 @@ class PdfName extends PdfDataType {
   final String value;
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     assert(value[0] == '/');
     final bytes = <int>[];
     for (final c in value.codeUnits) {
@@ -404,7 +407,7 @@ class PdfNull extends PdfDataType {
   const PdfNull();
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     s.putString('null');
   }
 
@@ -425,7 +428,7 @@ class PdfIndirect extends PdfDataType {
   final int gen;
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     s.putString('$ser $gen R');
   }
 
@@ -465,21 +468,39 @@ class PdfArray<T extends PdfDataType> extends PdfDataType {
   }
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
+    if (indent != null) {
+      s.putBytes(List<int>.filled(indent, 0x20));
+      indent += _kIndentSize;
+    }
     s.putString('[');
     if (values.isNotEmpty) {
       for (var n = 0; n < values.length; n++) {
         final val = values[n];
-        if (n > 0 &&
-            !(val is PdfName ||
-                val is PdfString ||
-                val is PdfArray ||
-                val is PdfDict)) {
-          s.putByte(0x20);
+        if (indent != null) {
+          s.putByte(0x0a);
+          if (val is! PdfDict && val is! PdfArray) {
+            s.putBytes(List<int>.filled(indent, 0x20));
+          }
+        } else {
+          if (n > 0 &&
+              !(val is PdfName ||
+                  val is PdfString ||
+                  val is PdfArray ||
+                  val is PdfDict)) {
+            s.putByte(0x20);
+          }
         }
-        val.output(s);
+        val.output(s, indent);
+      }
+      if (indent != null) {
+        s.putByte(0x0a);
       }
     }
+    if (indent != null) {
+      indent -= _kIndentSize;
+      s.putBytes(List<int>.filled(indent, 0x20));
+    }
     s.putString(']');
   }
 
@@ -544,15 +565,44 @@ class PdfDict<T extends PdfDataType> extends PdfDataType {
   }
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
+    if (indent != null) {
+      s.putBytes(List<int>.filled(indent, 0x20));
+    }
     s.putBytes(const <int>[0x3c, 0x3c]);
+    var len = 0;
+    var n = 1;
+    if (indent != null) {
+      s.putByte(0x0a);
+      indent += _kIndentSize;
+      len = values.keys.fold<int>(0, (p, e) => math.max(p, e.length));
+    }
     values.forEach((String k, T v) {
+      if (indent != null) {
+        s.putBytes(List<int>.filled(indent, 0x20));
+        n = len - k.length + 1;
+      }
       s.putString(k);
-      if (v is PdfNum || v is PdfBool || v is PdfNull || v is PdfIndirect) {
-        s.putByte(0x20);
+      if (indent != null) {
+        if (v is PdfDict || v is PdfArray) {
+          s.putByte(0x0a);
+        } else {
+          s.putBytes(List<int>.filled(n, 0x20));
+        }
+      } else {
+        if (v is PdfNum || v is PdfBool || v is PdfNull || v is PdfIndirect) {
+          s.putByte(0x20);
+        }
+      }
+      v.output(s, indent);
+      if (indent != null) {
+        s.putByte(0x0a);
       }
-      v.output(s);
     });
+    if (indent != null) {
+      indent -= _kIndentSize;
+      s.putBytes(List<int>.filled(indent, 0x20));
+    }
     s.putBytes(const <int>[0x3e, 0x3e]);
   }
 
@@ -633,7 +683,7 @@ class PdfDictStream extends PdfDict<PdfDataType> {
   final bool compress;
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     final _values = PdfDict(values);
 
     Uint8List? _data;
@@ -641,7 +691,7 @@ class PdfDictStream extends PdfDict<PdfDataType> {
     if (_values.containsKey('/Filter')) {
       // The data is already in the right format
       _data = data;
-    } else if (compress && object.pdfDocument.deflate != null) {
+    } else if (compress && object.pdfDocument.compress) {
       // Compress the data
       final newData = Uint8List.fromList(object.pdfDocument.deflate!(data));
       if (newData.lengthInBytes < data.lengthInBytes) {
@@ -668,7 +718,10 @@ class PdfDictStream extends PdfDict<PdfDataType> {
 
     _values['/Length'] = PdfNum(_data.length);
 
-    _values.output(s);
+    _values.output(s, indent);
+    if (indent != null) {
+      s.putByte(0x0a);
+    }
     s.putString('stream\n');
     s.putBytes(_data);
     s.putString('\nendstream\n');
@@ -681,7 +734,7 @@ class PdfColorType extends PdfDataType {
   final PdfColor color;
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     if (color is PdfColorCmyk) {
       final k = color as PdfColorCmyk;
       PdfArray.fromNum(<double>[
@@ -689,13 +742,13 @@ class PdfColorType extends PdfDataType {
         k.magenta,
         k.yellow,
         k.black,
-      ]).output(s);
+      ]).output(s, indent);
     } else {
       PdfArray.fromNum(<double>[
         color.red,
         color.green,
         color.blue,
-      ]).output(s);
+      ]).output(s, indent);
     }
   }
 

@@ -161,6 +161,8 @@ class PdfDocument {
 
   Uint8List? _documentID;
 
+  bool get compress => deflate != null;
+
   /// Generates the document ID
   Uint8List get documentID {
     if (_documentID == null) {
@@ -203,7 +205,7 @@ class PdfDocument {
 
   /// This writes the document to an OutputStream.
   Future<void> _write(PdfStream os) async {
-    final pos = PdfOutput(os, version);
+    final pos = PdfOutput(os, version, compress);
 
     // Write each object to the [PdfStream]. We call via the output
     // as that builds the xref table

@@ -109,6 +109,10 @@ class PdfGraphicState {
   /// Color transfer function
   final PdfFunction? transferFunction;
 
+  @override
+  String toString() =>
+      '$runtimeType fillOpacity:$fillOpacity strokeOpacity:$strokeOpacity blendMode:$blendMode softMask:$softMask transferFunction:$transferFunction';
+
   PdfDict output() {
     final params = PdfDict();
 

@@ -122,33 +122,75 @@ class PdfGraphics {
   /// Draw a surface on the previously defined shape
   /// set evenOdd to false to use the nonzero winding number rule to determine the region to fill and to true to use the even-odd rule to determine the region to fill
   void fillPath({bool evenOdd = false}) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('fillPath evenOdd:$evenOdd');
+      }
+      return true;
+    }());
+
     _buf.putString('f${evenOdd ? '*' : ''}\n');
   }
 
   /// Draw the contour of the previously defined shape
   void strokePath({bool close = false}) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('strokePath close:$close');
+      }
+      return true;
+    }());
+
     _buf.putString('${close ? 's' : 'S'}\n');
   }
 
   /// Close the path with a line
   void closePath() {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('closePath');
+      }
+      return true;
+    }());
+
     _buf.putString('h\n');
   }
 
   /// Create a clipping surface from the previously defined shape,
   /// to prevent any further drawing outside
   void clipPath({bool evenOdd = false, bool end = true}) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('clipPath evenOdd:$evenOdd end:$end');
+      }
+      return true;
+    }());
+
     _buf.putString('W${evenOdd ? '*' : ''}${end ? ' n' : ''}\n');
   }
 
   /// Draw a surface on the previously defined shape and then draw the contour
   /// set evenOdd to false to use the nonzero winding number rule to determine the region to fill and to true to use the even-odd rule to determine the region to fill
   void fillAndStrokePath({bool evenOdd = false, bool close = false}) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('fillAndStrokePath evenOdd:$evenOdd close:$close');
+      }
+      return true;
+    }());
+
     _buf.putString('${close ? 'b' : 'B'}${evenOdd ? '*' : ''}\n');
   }
 
   /// Apply a shader
   void applyShader(PdfShading shader) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('applyShader');
+      }
+      return true;
+    }());
+
     // The shader needs to be registered in the page resources
     _page.addShader(shader);
     _buf.putString('${shader.name} sh\n');
@@ -160,6 +202,13 @@ class PdfGraphics {
   /// When using [PdfPage], you can create another fresh Graphics instance,
   /// which will draw over this one.
   void restoreContext() {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('restoreContext');
+      }
+      return true;
+    }());
+
     if (_contextQueue.isNotEmpty) {
       // restore graphics context
       _buf.putString('Q\n');
@@ -169,12 +218,26 @@ class PdfGraphics {
 
   /// Save the graphc context
   void saveContext() {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('saveContext');
+      }
+      return true;
+    }());
+
     _buf.putString('q\n');
     _contextQueue.addLast(_context.copy());
   }
 
   /// Draws an image onto the page.
   void drawImage(PdfImage img, double x, double y, [double? w, double? h]) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('drawImage x:$x y:$y');
+      }
+      return true;
+    }());
+
     w ??= img.width.toDouble();
     h ??= img.height.toDouble() * w / img.width.toDouble();
 
@@ -215,6 +278,13 @@ class PdfGraphics {
 
   /// Draws a line between two coordinates.
   void drawLine(double x1, double y1, double x2, double y2) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('drawLine x1:$x1 y1:$y1 x2:$x2 y2:$y2');
+      }
+      return true;
+    }());
+
     moveTo(x1, y1);
     lineTo(x2, y2);
   }
@@ -224,6 +294,13 @@ class PdfGraphics {
   /// Use clockwise=false to draw the inside of a donnnut
   void drawEllipse(double x, double y, double r1, double r2,
       {bool clockwise = true}) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('drawEllipse x:$x y:$y r1:$r1 r2:$r2');
+      }
+      return true;
+    }());
+
     moveTo(x, y - r2);
     if (clockwise) {
       curveTo(x + _m4 * r1, y - r2, x + r1, y - _m4 * r2, x + r1, y);
@@ -245,6 +322,13 @@ class PdfGraphics {
     double w,
     double h,
   ) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('drawRect x:$x y:$y w:$w h:$h');
+      }
+      return true;
+    }());
+
     PdfNumList([x, y, w, h]).output(_buf);
     _buf.putString(' re\n');
   }
@@ -256,6 +340,13 @@ class PdfGraphics {
 
   /// Draws a Rounded Rectangle
   void drawRRect(double x, double y, double w, double h, double rv, double rh) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('drawRRect x:$x y:$y w:$w h:$h rv:$rv rh:$rh');
+      }
+      return true;
+    }());
+
     moveTo(x, y + rv);
     curveTo(x, y - _m4 * rv + rv, x - _m4 * rh + rh, y, x + rh, y);
     lineTo(x + w - rh, y);
@@ -278,6 +369,13 @@ class PdfGraphics {
     PdfTextRenderingMode? mode = PdfTextRenderingMode.fill,
     double? rise,
   }) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setFont');
+      }
+      return true;
+    }());
+
     _buf.putString('${font.name} ');
     PdfNum(size).output(_buf);
     _buf.putString(' Tf\n');
@@ -315,6 +413,13 @@ class PdfGraphics {
     PdfTextRenderingMode mode = PdfTextRenderingMode.fill,
     double rise = 0,
   }) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('drawString x:$x y:$y size:$size "$s"');
+      }
+      return true;
+    }());
+
     _page.addFont(font);
 
     _buf.putString('BT ');
@@ -332,6 +437,13 @@ class PdfGraphics {
   }
 
   void reset() {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('reset');
+      }
+      return true;
+    }());
+
     _buf.putString('0 Tr\n');
   }
 
@@ -343,6 +455,13 @@ class PdfGraphics {
 
   /// Sets the fill color for drawing
   void setFillColor(PdfColor? color) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setFillColor ${color?.toHex()}');
+      }
+      return true;
+    }());
+
     if (color is PdfColorCmyk) {
       PdfNumList(<double>[color.cyan, color.magenta, color.yellow, color.black])
           .output(_buf);
@@ -355,6 +474,13 @@ class PdfGraphics {
 
   /// Sets the stroke color for drawing
   void setStrokeColor(PdfColor? color) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setStrokeColor ${color?.toHex()}');
+      }
+      return true;
+    }());
+
     if (color is PdfColorCmyk) {
       PdfNumList(<double>[color.cyan, color.magenta, color.yellow, color.black])
           .output(_buf);
@@ -367,6 +493,13 @@ class PdfGraphics {
 
   /// Sets the fill pattern for drawing
   void setFillPattern(PdfPattern pattern) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setFillPattern');
+      }
+      return true;
+    }());
+
     // The shader needs to be registered in the page resources
     _page.addPattern(pattern);
     _buf.putString('/Pattern cs${pattern.name} scn\n');
@@ -374,6 +507,13 @@ class PdfGraphics {
 
   /// Sets the stroke pattern for drawing
   void setStrokePattern(PdfPattern pattern) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setStrokePattern');
+      }
+      return true;
+    }());
+
     // The shader needs to be registered in the page resources
     _page.addPattern(pattern);
     _buf.putString('/Pattern CS${pattern.name} SCN\n');
@@ -381,12 +521,26 @@ class PdfGraphics {
 
   /// Set the graphic state for drawing
   void setGraphicState(PdfGraphicState state) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setGraphicState $state');
+      }
+      return true;
+    }());
+
     final name = _page.stateName(state);
     _buf.putString('$name gs\n');
   }
 
   /// Set the transformation Matrix
   void setTransform(Matrix4 t) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setTransform\n$t');
+      }
+      return true;
+    }());
+
     final s = t.storage;
     PdfNumList(<double>[s[0], s[1], s[4], s[5], s[12], s[13]]).output(_buf);
     _buf.putString(' cm\n');
@@ -400,12 +554,26 @@ class PdfGraphics {
 
   /// This adds a line segment to the current path
   void lineTo(double x, double y) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('lineTo x:$x y:$y');
+      }
+      return true;
+    }());
+
     PdfNumList([x, y]).output(_buf);
     _buf.putString(' l\n');
   }
 
   /// This moves the current drawing point.
   void moveTo(double x, double y) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('moveTo x:$x y:$y');
+      }
+      return true;
+    }());
+
     PdfNumList([x, y]).output(_buf);
     _buf.putString(' m\n');
   }
@@ -415,6 +583,13 @@ class PdfGraphics {
   /// and (x2,y2) as the control point at the end of the curve.
   void curveTo(
       double x1, double y1, double x2, double y2, double x3, double y3) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('curveTo x1:$x1 y1:$y1 x2:$x2 y2:$y2 x3:$x3 y3:$y3');
+      }
+      return true;
+    }());
+
     PdfNumList([x1, y1, x2, y2, x3, y3]).output(_buf);
     _buf.putString(' c\n');
   }
@@ -576,22 +751,50 @@ class PdfGraphics {
 
   /// Set line starting and ending cap type
   void setLineCap(PdfLineCap cap) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setLineCap $cap');
+      }
+      return true;
+    }());
+
     _buf.putString('${cap.index} J\n');
   }
 
   /// Set line join type
   void setLineJoin(PdfLineJoin join) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setLineJoin $join');
+      }
+      return true;
+    }());
+
     _buf.putString('${join.index} j\n');
   }
 
   /// Set line width
   void setLineWidth(double width) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setLineWidth $width');
+      }
+      return true;
+    }());
+
     PdfNum(width).output(_buf);
     _buf.putString(' w\n');
   }
 
   /// Set line joint miter limit, applies if the
   void setMiterLimit(double limit) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setMiterLimit $limit');
+      }
+      return true;
+    }());
+
     assert(limit >= 1.0);
     PdfNum(limit).output(_buf);
     _buf.putString(' M\n');
@@ -602,16 +805,37 @@ class PdfGraphics {
   ///
   /// Example: [2 1] will create a dash pattern with 2 on, 1 off, 2 on, 1 off, ...
   void setLineDashPattern([List<num> array = const <num>[], int phase = 0]) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('setLineDashPattern $array phase:$phase');
+      }
+      return true;
+    }());
+
     PdfArray.fromNum(array).output(_buf);
     _buf.putString(' $phase d\n');
   }
 
   void markContentBegin(PdfName tag) {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('markContentBegin');
+      }
+      return true;
+    }());
+
     tag.output(_buf);
     _buf.putString(' BMC\n');
   }
 
   void markContentEnd() {
+    assert(() {
+      if (!_page.pdfDocument.compress) {
+        _buf.putComment('markContentEnd');
+      }
+      return true;
+    }());
+
     _buf.putString('EMC\n');
   }
 }

@@ -60,11 +60,20 @@ abstract class PdfObject<T extends PdfDataType> {
   /// The write method should call this before writing anything to the
   /// OutputStream. This will send the standard header for each object.
   void _writeStart(PdfStream os) {
+    assert(() {
+      if (!pdfDocument.compress) {
+        os.putComment('');
+        os.putComment('-' * 78);
+        os.putComment('$runtimeType');
+      }
+      return true;
+    }());
+
     os.putString('$objser $objgen obj\n');
   }
 
   void writeContent(PdfStream os) {
-    params.output(os);
+    params.output(os, pdfDocument.compress ? null : 0);
     os.putByte(0x0a);
   }
 

@@ -37,7 +37,7 @@ class PdfObjectDict extends PdfObject<PdfDict> {
   @override
   void writeContent(PdfStream os) {
     if (params.isNotEmpty) {
-      params.output(os);
+      params.output(os, pdfDocument.compress ? null : 0);
       os.putByte(0x0a);
     }
   }

@@ -41,6 +41,6 @@ class PdfObjectStream extends PdfObjectDict {
       isBinary: isBinary,
       values: params.values,
       data: buf.output(),
-    ).output(os);
+    ).output(os, pdfDocument.compress ? null : 0);
   }
 }

@@ -62,6 +62,9 @@ class PdfSoftMask {
 
   PdfBaseFunction? _tr;
 
+  @override
+  String toString() => '$runtimeType';
+
   PdfDict output() {
     final params = PdfDict({
       '/S': const PdfName('/Luminosity'),

@@ -34,7 +34,7 @@ class PdfUnicodeCmap extends PdfObjectStream {
       cmap.fillRange(1, cmap.length, 0x20);
     }
 
-    buf.putString('/CIDInit/ProcSet findresource begin\n'
+    buf.putString('/CIDInit/ProcSet\nfindresource begin\n'
         '12 dict begin\n'
         'begincmap\n'
         '/CIDSystemInfo<<\n'

@@ -27,7 +27,7 @@ import 'xref.dart';
 /// PDF document writer
 class PdfOutput {
   /// This creates a Pdf [PdfStream]
-  PdfOutput(this.os, this.version) {
+  PdfOutput(this.os, this.version, bool compress) {
     String v;
     switch (version) {
       case PdfVersion.pdf_1_4:
@@ -40,8 +40,22 @@ class PdfOutput {
 
     os.putString('%PDF-$v\n');
     os.putBytes(const <int>[0x25, 0xC2, 0xA5, 0xC2, 0xB1, 0xC3, 0xAB, 0x0A]);
+    assert(() {
+      if (!compress) {
+        _stopwatch = Stopwatch()..start();
+        os.putComment('');
+        os.putComment('Verbose dart_pdf');
+        os.putComment('Creation date: ${DateTime.now()}');
+        _comment = os.offset;
+        os.putBytes(List<int>.filled(120, 0x20));
+      }
+      return true;
+    }());
   }
 
+  late final Stopwatch _stopwatch;
+  var _comment = 0;
+
   /// Pdf version to output
   final PdfVersion version;
 
@@ -129,9 +143,32 @@ class PdfOutput {
       os.putByte(0x0a);
     }
 
+    assert(() {
+      if (!rootID!.pdfDocument.compress) {
+        os.putComment('');
+        os.putComment('-' * 78);
+      }
+      return true;
+    }());
+
     // the reference to the xref object
     os.putString('startxref\n$_xref\n%%EOF\n');
 
+    assert(() {
+      if (!rootID!.pdfDocument.compress) {
+        _stopwatch.stop();
+        final h = PdfStream();
+        h.putComment(
+            'Creation time: ${_stopwatch.elapsed.inMicroseconds / Duration.microsecondsPerSecond} seconds');
+        h.putComment('File size: ${os.offset} bytes');
+        h.putComment('Pages: ${rootID!.pdfDocument.pdfPageList.pages.length}');
+        h.putComment('Objects: ${xref.offsets.length}');
+
+        os.setBytes(_comment, h.output());
+      }
+      return true;
+    }());
+
     if (signatureID != null) {
       await signatureID!.writeSignature(os);
     }

@@ -68,4 +68,16 @@ class PdfStream {
     }());
     putBytes(s!.codeUnits);
   }
+
+  void putComment(String s) {
+    if (s.isEmpty) {
+      putByte(0x0a);
+    } else {
+      for (final l in s.split('\n')) {
+        if (l.isNotEmpty) {
+          putBytes('% $l\n'.codeUnits);
+        }
+      }
+    }
+  }
 }

@@ -107,7 +107,7 @@ class PdfXrefTable extends PdfDataType {
   }
 
   @override
-  void output(PdfStream s) {
+  void output(PdfStream s, [int? indent]) {
     s.putString('xref\n');
 
     // Now scan through the offsets list. They should be in sequence.
@@ -153,8 +153,6 @@ class PdfXrefTable extends PdfDataType {
     // Sort all references
     offsets.sort((a, b) => a.id.compareTo(b.id));
 
-    s.putString('$id 0 obj\n');
-
     params['/Type'] = const PdfName('/XRef');
     params['/Size'] = PdfNum(id + 1);
 
@@ -200,12 +198,22 @@ class PdfXrefTable extends PdfDataType {
     }
 
     // Write the object
+    assert(() {
+      if (!object.pdfDocument.compress) {
+        s.putComment('');
+        s.putComment('-' * 78);
+        s.putComment('$runtimeType $this');
+      }
+      return true;
+    }());
+    s.putString('$id 0 obj\n');
+
     PdfDictStream(
       object: object,
       data: o.buffer.asUint8List(),
       isBinary: false,
       encrypt: false,
       values: params.values,
-    ).output(s);
+    ).output(s, object.pdfDocument.compress ? null : 0);
   }
 }