Implement donnut chart

@@ -14,6 +14,7 @@
 - Improve TextOverflow support
 - Fix Table horizontalInside borders
 - Improve PieChart default colors
+- Implement donnut chart
 
 ## 3.2.0
 

@@ -100,7 +100,7 @@ class _PdfGraphicsContext {
 /// Pdf drawing operations
 class PdfGraphics {
   /// Create a new graphic canvas
-  PdfGraphics(this._page, this.buf) {
+  PdfGraphics(this._page, this._buf) {
     _context = _PdfGraphicsContext(ctm: Matrix4.identity());
   }
 
@@ -114,7 +114,7 @@ class PdfGraphics {
   final PdfGraphicStream _page;
 
   /// Buffer where to write the graphic operations
-  final PdfStream buf;
+  final PdfStream _buf;
 
   /// Default font if none selected
   PdfFont? get defaultFont => _page.getDefaultFont();
@@ -122,36 +122,36 @@ 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}) {
-    buf.putString('f${evenOdd ? '*' : ''}\n');
+    _buf.putString('f${evenOdd ? '*' : ''}\n');
   }
 
   /// Draw the contour of the previously defined shape
   void strokePath({bool close = false}) {
-    buf.putString('${close ? 's' : 'S'}\n');
+    _buf.putString('${close ? 's' : 'S'}\n');
   }
 
   /// Close the path with a line
   void closePath() {
-    buf.putString('h\n');
+    _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}) {
-    buf.putString('W${evenOdd ? '*' : ''}${end ? ' n' : ''}\n');
+    _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}) {
-    buf.putString('${close ? 'b' : 'B'}${evenOdd ? '*' : ''}\n');
+    _buf.putString('${close ? 'b' : 'B'}${evenOdd ? '*' : ''}\n');
   }
 
   /// Apply a shader
   void applyShader(PdfShading shader) {
     // The shader needs to be registered in the page resources
     _page.addShader(shader);
-    buf.putString('${shader.name} sh\n');
+    _buf.putString('${shader.name} sh\n');
   }
 
   /// This releases any resources used by this Graphics object. You must use
@@ -162,14 +162,14 @@ class PdfGraphics {
   void restoreContext() {
     if (_contextQueue.isNotEmpty) {
       // restore graphics context
-      buf.putString('Q\n');
+      _buf.putString('Q\n');
       _context = _contextQueue.removeLast();
     }
   }
 
   /// Save the graphc context
   void saveContext() {
-    buf.putString('q\n');
+    _buf.putString('q\n');
     _contextQueue.addLast(_context.copy());
   }
 
@@ -182,35 +182,35 @@ class PdfGraphics {
     _page.addXObject(img);
 
     // q w 0 0 h x y cm % the coordinate matrix
-    buf.putString('q ');
+    _buf.putString('q ');
     switch (img.orientation) {
       case PdfImageOrientation.topLeft:
-        PdfNumList(<double>[w, 0, 0, h, x, y]).output(buf);
+        PdfNumList(<double>[w, 0, 0, h, x, y]).output(_buf);
         break;
       case PdfImageOrientation.topRight:
-        PdfNumList(<double>[-w, 0, 0, h, w + x, y]).output(buf);
+        PdfNumList(<double>[-w, 0, 0, h, w + x, y]).output(_buf);
         break;
       case PdfImageOrientation.bottomRight:
-        PdfNumList(<double>[-w, 0, 0, -h, w + x, h + y]).output(buf);
+        PdfNumList(<double>[-w, 0, 0, -h, w + x, h + y]).output(_buf);
         break;
       case PdfImageOrientation.bottomLeft:
-        PdfNumList(<double>[w, 0, 0, -h, x, h + y]).output(buf);
+        PdfNumList(<double>[w, 0, 0, -h, x, h + y]).output(_buf);
         break;
       case PdfImageOrientation.leftTop:
-        PdfNumList(<double>[0, -h, -w, 0, w + x, h + y]).output(buf);
+        PdfNumList(<double>[0, -h, -w, 0, w + x, h + y]).output(_buf);
         break;
       case PdfImageOrientation.rightTop:
-        PdfNumList(<double>[0, -h, w, 0, x, h + y]).output(buf);
+        PdfNumList(<double>[0, -h, w, 0, x, h + y]).output(_buf);
         break;
       case PdfImageOrientation.rightBottom:
-        PdfNumList(<double>[0, h, w, 0, x, y]).output(buf);
+        PdfNumList(<double>[0, h, w, 0, x, y]).output(_buf);
         break;
       case PdfImageOrientation.leftBottom:
-        PdfNumList(<double>[0, h, -w, 0, w + x, y]).output(buf);
+        PdfNumList(<double>[0, h, -w, 0, w + x, y]).output(_buf);
         break;
     }
 
-    buf.putString(' cm ${img.name} Do Q\n');
+    _buf.putString(' cm ${img.name} Do Q\n');
   }
 
   /// Draws a line between two coordinates.
@@ -220,12 +220,22 @@ class PdfGraphics {
   }
 
   /// Draws an ellipse
-  void drawEllipse(double x, double y, double r1, double r2) {
+  ///
+  /// Use clockwise=false to draw the inside of a donnnut
+  void drawEllipse(double x, double y, double r1, double r2,
+      {bool clockwise = true}) {
     moveTo(x, y - r2);
-    curveTo(x + _m4 * r1, y - r2, x + r1, y - _m4 * r2, x + r1, y);
-    curveTo(x + r1, y + _m4 * r2, x + _m4 * r1, y + r2, x, y + r2);
-    curveTo(x - _m4 * r1, y + r2, x - r1, y + _m4 * r2, x - r1, y);
-    curveTo(x - r1, y - _m4 * r2, x - _m4 * r1, y - r2, x, y - r2);
+    if (clockwise) {
+      curveTo(x + _m4 * r1, y - r2, x + r1, y - _m4 * r2, x + r1, y);
+      curveTo(x + r1, y + _m4 * r2, x + _m4 * r1, y + r2, x, y + r2);
+      curveTo(x - _m4 * r1, y + r2, x - r1, y + _m4 * r2, x - r1, y);
+      curveTo(x - r1, y - _m4 * r2, x - _m4 * r1, y - r2, x, y - r2);
+    } else {
+      curveTo(x - _m4 * r1, y - r2, x - r1, y - _m4 * r2, x - r1, y);
+      curveTo(x - r1, y + _m4 * r2, x - _m4 * r1, y + r2, x, y + r2);
+      curveTo(x + _m4 * r1, y + r2, x + r1, y + _m4 * r2, x + r1, y);
+      curveTo(x + r1, y - _m4 * r2, x + _m4 * r1, y - r2, x, y - r2);
+    }
   }
 
   /// Draws a Rectangle
@@ -235,8 +245,8 @@ class PdfGraphics {
     double w,
     double h,
   ) {
-    PdfNumList([x, y, w, h]).output(buf);
-    buf.putString(' re\n');
+    PdfNumList([x, y, w, h]).output(_buf);
+    _buf.putString(' re\n');
   }
 
   /// Draws a Rectangle
@@ -268,27 +278,27 @@ class PdfGraphics {
     PdfTextRenderingMode? mode = PdfTextRenderingMode.fill,
     double? rise,
   }) {
-    buf.putString('${font.name} ');
-    PdfNum(size).output(buf);
-    buf.putString(' Tf\n');
+    _buf.putString('${font.name} ');
+    PdfNum(size).output(_buf);
+    _buf.putString(' Tf\n');
     if (charSpace != null) {
-      PdfNum(charSpace).output(buf);
-      buf.putString(' Tc\n');
+      PdfNum(charSpace).output(_buf);
+      _buf.putString(' Tc\n');
     }
     if (wordSpace != null) {
-      PdfNum(wordSpace).output(buf);
-      buf.putString(' Tw\n');
+      PdfNum(wordSpace).output(_buf);
+      _buf.putString(' Tw\n');
     }
     if (scale != null) {
-      PdfNum(scale * 100).output(buf);
-      buf.putString(' Tz\n');
+      PdfNum(scale * 100).output(_buf);
+      _buf.putString(' Tz\n');
     }
     if (rise != null) {
-      PdfNum(rise).output(buf);
-      buf.putString(' Ts\n');
+      PdfNum(rise).output(_buf);
+      _buf.putString(' Ts\n');
     }
     if (mode != PdfTextRenderingMode.fill) {
-      buf.putString('${mode!.index} Tr\n');
+      _buf.putString('${mode!.index} Tr\n');
     }
   }
 
@@ -307,22 +317,22 @@ class PdfGraphics {
   }) {
     _page.addFont(font);
 
-    buf.putString('BT ');
-    PdfNumList([x, y]).output(buf);
-    buf.putString(' Td ');
+    _buf.putString('BT ');
+    PdfNumList([x, y]).output(_buf);
+    _buf.putString(' Td ');
     setFont(font, size,
         charSpace: charSpace,
         mode: mode,
         rise: rise,
         scale: scale,
         wordSpace: wordSpace);
-    buf.putString('[');
-    font.putText(buf, s);
-    buf.putString(']TJ ET\n');
+    _buf.putString('[');
+    font.putText(_buf, s);
+    _buf.putString(']TJ ET\n');
   }
 
   void reset() {
-    buf.putString('0 Tr\n');
+    _buf.putString('0 Tr\n');
   }
 
   /// Sets the color for drawing
@@ -335,11 +345,11 @@ class PdfGraphics {
   void setFillColor(PdfColor? color) {
     if (color is PdfColorCmyk) {
       PdfNumList(<double>[color.cyan, color.magenta, color.yellow, color.black])
-          .output(buf);
-      buf.putString(' k\n');
+          .output(_buf);
+      _buf.putString(' k\n');
     } else {
-      PdfNumList(<double>[color!.red, color.green, color.blue]).output(buf);
-      buf.putString(' rg\n');
+      PdfNumList(<double>[color!.red, color.green, color.blue]).output(_buf);
+      _buf.putString(' rg\n');
     }
   }
 
@@ -347,11 +357,11 @@ class PdfGraphics {
   void setStrokeColor(PdfColor? color) {
     if (color is PdfColorCmyk) {
       PdfNumList(<double>[color.cyan, color.magenta, color.yellow, color.black])
-          .output(buf);
-      buf.putString(' K\n');
+          .output(_buf);
+      _buf.putString(' K\n');
     } else {
-      PdfNumList(<double>[color!.red, color.green, color.blue]).output(buf);
-      buf.putString(' RG\n');
+      PdfNumList(<double>[color!.red, color.green, color.blue]).output(_buf);
+      _buf.putString(' RG\n');
     }
   }
 
@@ -359,27 +369,27 @@ class PdfGraphics {
   void setFillPattern(PdfPattern pattern) {
     // The shader needs to be registered in the page resources
     _page.addPattern(pattern);
-    buf.putString('/Pattern cs${pattern.name} scn\n');
+    _buf.putString('/Pattern cs${pattern.name} scn\n');
   }
 
   /// Sets the stroke pattern for drawing
   void setStrokePattern(PdfPattern pattern) {
     // The shader needs to be registered in the page resources
     _page.addPattern(pattern);
-    buf.putString('/Pattern CS${pattern.name} SCN\n');
+    _buf.putString('/Pattern CS${pattern.name} SCN\n');
   }
 
   /// Set the graphic state for drawing
   void setGraphicState(PdfGraphicState state) {
     final name = _page.stateName(state);
-    buf.putString('$name gs\n');
+    _buf.putString('$name gs\n');
   }
 
   /// Set the transformation Matrix
   void setTransform(Matrix4 t) {
     final s = t.storage;
-    PdfNumList(<double>[s[0], s[1], s[4], s[5], s[12], s[13]]).output(buf);
-    buf.putString(' cm\n');
+    PdfNumList(<double>[s[0], s[1], s[4], s[5], s[12], s[13]]).output(_buf);
+    _buf.putString(' cm\n');
     _context.ctm.multiply(t);
   }
 
@@ -390,14 +400,14 @@ class PdfGraphics {
 
   /// This adds a line segment to the current path
   void lineTo(double x, double y) {
-    PdfNumList([x, y]).output(buf);
-    buf.putString(' l\n');
+    PdfNumList([x, y]).output(_buf);
+    _buf.putString(' l\n');
   }
 
   /// This moves the current drawing point.
   void moveTo(double x, double y) {
-    PdfNumList([x, y]).output(buf);
-    buf.putString(' m\n');
+    PdfNumList([x, y]).output(_buf);
+    _buf.putString(' m\n');
   }
 
   /// Draw a cubic bézier curve from the current point to (x3,y3)
@@ -405,8 +415,8 @@ 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) {
-    PdfNumList([x1, y1, x2, y2, x3, y3]).output(buf);
-    buf.putString(' c\n');
+    PdfNumList([x1, y1, x2, y2, x3, y3]).output(_buf);
+    _buf.putString(' c\n');
   }
 
   double _vectorAngle(double ux, double uy, double vx, double vy) {
@@ -566,25 +576,25 @@ class PdfGraphics {
 
   /// Set line starting and ending cap type
   void setLineCap(PdfLineCap cap) {
-    buf.putString('${cap.index} J\n');
+    _buf.putString('${cap.index} J\n');
   }
 
   /// Set line join type
   void setLineJoin(PdfLineJoin join) {
-    buf.putString('${join.index} j\n');
+    _buf.putString('${join.index} j\n');
   }
 
   /// Set line width
   void setLineWidth(double width) {
-    PdfNum(width).output(buf);
-    buf.putString(' w\n');
+    PdfNum(width).output(_buf);
+    _buf.putString(' w\n');
   }
 
   /// Set line joint miter limit, applies if the
   void setMiterLimit(double limit) {
     assert(limit >= 1.0);
-    PdfNum(limit).output(buf);
-    buf.putString(' M\n');
+    PdfNum(limit).output(_buf);
+    _buf.putString(' M\n');
   }
 
   /// The dash array shall be cycled through, adding up the lengths of dashes and gaps.
@@ -592,8 +602,17 @@ 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]) {
-    PdfArray.fromNum(array).output(buf);
-    buf.putString(' $phase d\n');
+    PdfArray.fromNum(array).output(_buf);
+    _buf.putString(' $phase d\n');
+  }
+
+  void markContentBegin(PdfName tag) {
+    tag.output(_buf);
+    _buf.putString(' BMC\n');
+  }
+
+  void markContentEnd() {
+    _buf.putString('EMC\n');
   }
 }
 

@@ -2,20 +2,21 @@
 
 import 'dart:math';
 
+import 'package:meta/meta.dart';
 import 'package:pdf/pdf.dart';
 import 'package:pdf/widgets.dart';
 import 'package:vector_math/vector_math_64.dart';
 
 class PieGrid extends ChartGrid {
-  PieGrid();
+  PieGrid({this.startAngle = 0});
 
-  late PdfRect gridBox;
+  /// Start angle for the first [PieDataSet]
+  final double startAngle;
 
-  late double total;
+  late double _radius;
 
-  late double unit;
-
-  late double pieSize;
+  /// Nominal radius of a pie slice
+  double get radius => _radius;
 
   @override
   void layout(Context context, BoxConstraints constraints,
@@ -25,19 +26,19 @@ class PieGrid extends ChartGrid {
     final datasets = Chart.of(context).datasets;
     final size = constraints.biggest;
 
-    gridBox = PdfRect(0, 0, size.x, size.y);
+    final _gridBox = PdfRect(0, 0, size.x, size.y);
 
-    total = 0.0;
+    var _total = 0.0;
 
     for (final dataset in datasets) {
-      assert(dataset is PieDataSet, 'Use only PieDataSet with a PieGrid');
+      assert(dataset is PieDataSet, 'Use only PieDataset with a PieGrid');
       if (dataset is PieDataSet) {
-        total += dataset.value;
+        _total += dataset.value;
       }
     }
 
-    unit = pi / total * 2;
-    var angle = 0.0;
+    final unit = pi / _total * 2;
+    var angle = startAngle;
 
     for (final dataset in datasets) {
       if (dataset is PieDataSet) {
@@ -47,19 +48,19 @@ class PieGrid extends ChartGrid {
       }
     }
 
-    pieSize = min(gridBox.width / 2, gridBox.height / 2);
+    _radius = min(_gridBox.width / 2, _gridBox.height / 2);
     var reduce = false;
 
     do {
       reduce = false;
       for (final dataset in datasets) {
         if (dataset is PieDataSet) {
-          dataset.layout(context, BoxConstraints.tight(gridBox.size));
+          dataset.layout(context, BoxConstraints.tight(_gridBox.size));
           assert(dataset.box != null);
-          if (pieSize > 20 &&
-              (dataset.box!.width > gridBox.width ||
-                  dataset.box!.height > gridBox.height)) {
-            pieSize -= 10;
+          if (_radius > 20 &&
+              (dataset.box!.width > _gridBox.width ||
+                  dataset.box!.height > _gridBox.height)) {
+            _radius -= 10;
             reduce = true;
             break;
           }
@@ -129,7 +130,10 @@ class PieDataSet extends Dataset {
     PdfColor? legendLineColor,
     Widget? legendWidget,
     this.legendOffset = 20,
-  })  : drawBorder = drawBorder ?? borderColor != null && color != borderColor,
+    this.innerRadius = 0,
+  })  : assert(innerRadius >= 0),
+        assert(offset >= 0),
+        drawBorder = drawBorder ?? borderColor != null && color != borderColor,
         assert((drawBorder ?? borderColor != null && color != borderColor) ||
             drawSurface),
         _legendWidget = legendWidget,
@@ -168,6 +172,8 @@ class PieDataSet extends Dataset {
 
   final PdfColor legendLineColor;
 
+  final double innerRadius;
+
   PdfPoint? _legendAnchor;
   PdfPoint? _legendPivot;
   PdfPoint? _legendStart;
@@ -180,7 +186,7 @@ class PieDataSet extends Dataset {
     final _offset = _isFullCircle ? 0 : offset;
 
     final grid = Chart.of(context).grid as PieGrid;
-    final len = grid.pieSize + _offset;
+    final len = grid.radius + _offset;
     var x = -len;
     var y = -len;
     var w = len * 2;
@@ -217,7 +223,7 @@ class PieDataSet extends Dataset {
 
     if (_legendWidget != null) {
       _legendWidget!.layout(context,
-          BoxConstraints(maxWidth: grid.pieSize, maxHeight: grid.pieSize));
+          BoxConstraints(maxWidth: grid.radius, maxHeight: grid.radius));
       assert(_legendWidget!.box != null);
 
       final ls = _legendWidget!.box!.size;
@@ -226,13 +232,13 @@ class PieDataSet extends Dataset {
 
       switch (lp) {
         case PieLegendPosition.outside:
-          final o = grid.pieSize + legendOffset;
+          final o = grid.radius + legendOffset;
           final cx = sin(bisect) * (_offset + o);
           final cy = cos(bisect) * (_offset + o);
 
           _legendStart = PdfPoint(
-            sin(bisect) * (_offset + grid.pieSize + legendOffset * 0.1),
-            cos(bisect) * (_offset + grid.pieSize + legendOffset * 0.1),
+            sin(bisect) * (_offset + grid.radius + legendOffset * 0.1),
+            cos(bisect) * (_offset + grid.radius + legendOffset * 0.1),
           );
 
           _legendPivot = PdfPoint(cx, cy);
@@ -269,9 +275,23 @@ class PieDataSet extends Dataset {
           }
           break;
         case PieLegendPosition.inside:
-          final o = _isFullCircle ? 0 : grid.pieSize * 2 / 3;
-          final cx = sin(bisect) * (_offset + o);
-          final cy = cos(bisect) * (_offset + o);
+          final double o;
+          final double cx;
+          final double cy;
+          if (innerRadius == 0) {
+            o = _isFullCircle ? 0 : grid.radius * 2 / 3;
+            cx = sin(bisect) * (_offset + o);
+            cy = cos(bisect) * (_offset + o);
+          } else {
+            o = (grid.radius + innerRadius) / 2;
+            if (_isFullCircle) {
+              cx = 0;
+              cy = o;
+            } else {
+              cx = sin(bisect) * (_offset + o);
+              cy = cos(bisect) * (_offset + o);
+            }
+          }
           _legendWidget!.box = PdfRect.fromPoints(
               PdfPoint(
                 cx - ls.x / 2,
@@ -287,7 +307,7 @@ class PieDataSet extends Dataset {
     box = PdfRect(x, y, w, h);
   }
 
-  void _shape(Context context) {
+  void _paintSliceShape(Context context) {
     final grid = Chart.of(context).grid as PieGrid;
 
     final bisect = (angleStart + angleEnd) / 2;
@@ -295,28 +315,69 @@ class PieDataSet extends Dataset {
     final cx = sin(bisect) * offset;
     final cy = cos(bisect) * offset;
 
-    final sx = cx + sin(angleStart) * grid.pieSize;
-    final sy = cy + cos(angleStart) * grid.pieSize;
-    final ex = cx + sin(angleEnd) * grid.pieSize;
-    final ey = cy + cos(angleEnd) * grid.pieSize;
+    final sx = cx + sin(angleStart) * grid.radius;
+    final sy = cy + cos(angleStart) * grid.radius;
+    final ex = cx + sin(angleEnd) * grid.radius;
+    final ey = cy + cos(angleEnd) * grid.radius;
 
     if (_isFullCircle) {
-      context.canvas.drawEllipse(0, 0, grid.pieSize, grid.pieSize);
+      context.canvas.drawEllipse(0, 0, grid.radius, grid.radius);
     } else {
       context.canvas
         ..moveTo(cx, cy)
         ..lineTo(sx, sy)
-        ..bezierArc(sx, sy, grid.pieSize, grid.pieSize, ex, ey,
+        ..bezierArc(sx, sy, grid.radius, grid.radius, ex, ey,
             large: angleEnd - angleStart > pi);
     }
   }
 
+  void _paintDonnutShape(Context context) {
+    final grid = Chart.of(context).grid as PieGrid;
+
+    final bisect = (angleStart + angleEnd) / 2;
+
+    final cx = sin(bisect) * offset;
+    final cy = cos(bisect) * offset;
+
+    final stx = cx + sin(angleStart) * grid.radius;
+    final sty = cy + cos(angleStart) * grid.radius;
+    final etx = cx + sin(angleEnd) * grid.radius;
+    final ety = cy + cos(angleEnd) * grid.radius;
+    final sbx = cx + sin(angleStart) * innerRadius;
+    final sby = cy + cos(angleStart) * innerRadius;
+    final ebx = cx + sin(angleEnd) * innerRadius;
+    final eby = cy + cos(angleEnd) * innerRadius;
+
+    if (_isFullCircle) {
+      context.canvas.drawEllipse(0, 0, grid.radius, grid.radius);
+      context.canvas
+          .drawEllipse(0, 0, innerRadius, innerRadius, clockwise: false);
+    } else {
+      context.canvas
+        ..moveTo(stx, sty)
+        ..bezierArc(stx, sty, grid.radius, grid.radius, etx, ety,
+            large: angleEnd - angleStart > pi)
+        ..lineTo(ebx, eby)
+        ..bezierArc(ebx, eby, innerRadius, innerRadius, sbx, sby,
+            large: angleEnd - angleStart > pi, sweep: true)
+        ..lineTo(stx, sty);
+    }
+  }
+
+  void _paintShape(Context context) {
+    if (innerRadius == 0) {
+      _paintSliceShape(context);
+    } else {
+      _paintDonnutShape(context);
+    }
+  }
+
   @override
   void paintBackground(Context context) {
     super.paint(context);
 
     if (drawSurface) {
-      _shape(context);
+      _paintShape(context);
       if (surfaceOpacity != 1) {
         context.canvas
           ..saveContext()
@@ -340,7 +401,7 @@ class PieDataSet extends Dataset {
     super.paint(context);
 
     if (drawBorder) {
-      _shape(context);
+      _paintShape(context);
       context.canvas
         ..setLineWidth(borderWidth)
         ..setLineJoin(PdfLineJoin.round)
@@ -349,6 +410,7 @@ class PieDataSet extends Dataset {
     }
   }
 
+  @protected
   void paintLegend(Context context) {
     if (legendPosition != PieLegendPosition.none && _legendWidget != null) {
       if (_legendAnchor != null &&
@@ -379,8 +441,8 @@ class PieDataSet extends Dataset {
 
     final bisect = (angleStart + angleEnd) / 2;
 
-    final cx = sin(bisect) * (offset + grid.pieSize + legendOffset);
-    final cy = cos(bisect) * (offset + grid.pieSize + legendOffset);
+    final cx = sin(bisect) * (offset + grid.radius + legendOffset);
+    final cy = cos(bisect) * (offset + grid.radius + legendOffset);
 
     if (_legendWidget != null) {
       context.canvas

@@ -17,6 +17,7 @@
 import 'dart:typed_data';
 
 import 'package:pdf/pdf.dart';
+import 'package:pdf/src/pdf/data_types.dart';
 import 'package:vector_math/vector_math_64.dart';
 
 import 'basic.dart';
@@ -294,7 +295,7 @@ class TextField extends StatelessWidget {
     if (value != null) {
       final canvas = tf.appearance(context.document, PdfAnnotAppearance.normal,
           matrix: mat, boundingBox: box);
-      canvas.buf.putString('/Tx BMC\n');
+      canvas.markContentBegin(const PdfName('/Tx'));
       Widget.draw(
         Text(value!, style: _textStyle),
         offset: PdfPoint.zero,
@@ -303,7 +304,7 @@ class TextField extends StatelessWidget {
         constraints:
             BoxConstraints.tightFor(width: box!.width, height: box!.height),
       );
-      canvas.buf.putString('EMC\n');
+      canvas.markContentEnd();
     }
 
     PdfAnnot(context.page, tf);

@@ -16,9 +16,9 @@
 
 import 'dart:io';
 
-import 'package:test/test.dart';
 import 'package:pdf/pdf.dart';
 import 'package:pdf/widgets.dart';
+import 'package:test/test.dart';
 
 late Document pdf;
 
@@ -213,6 +213,83 @@ void main() {
     });
   });
 
+  test('Standard PieChart', () {
+    const data = <String, double>{
+      'Wind': 8.4,
+      'Hydro': 7.4,
+      'Solar': 2.4,
+      'Biomass': 1.4,
+      'Geothermal': 0.4,
+      'Nuclear': 20,
+      'Coal': 19,
+      'Petroleum': 1,
+      'Natural gas': 40,
+    };
+    var color = 0;
+
+    pdf.addPage(
+      Page(
+        pageFormat: PdfPageFormat.standard.landscape,
+        build: (Context context) => Chart(
+          title: Text('Sources of U.S. electricity generation, 2020'),
+          grid: PieGrid(),
+          datasets: [
+            for (final item in data.entries)
+              PieDataSet(
+                legend: item.key,
+                value: item.value,
+                color: PdfColors
+                    .primaries[(color++) * 4 % PdfColors.primaries.length],
+                offset: color == 6 ? 30 : 0,
+              ),
+          ],
+        ),
+      ),
+    );
+  });
+
+  test('Donnuts PieChart', () {
+    const internalRadius = 150.0;
+    const data = <String, int>{
+      'Dogs': 5528,
+      'Birds': 2211,
+      'Rabbits': 3216,
+      'Ermine': 740,
+      'Cats': 8241,
+    };
+    var color = 0;
+    final total = data.values.fold<int>(0, (v, e) => v + e);
+
+    pdf.addPage(
+      Page(
+        pageFormat: PdfPageFormat.standard.landscape,
+        build: (Context context) => Stack(
+          alignment: Alignment.center,
+          children: [
+            Text(
+              'Pets',
+              textAlign: TextAlign.center,
+              style: const TextStyle(fontSize: 30),
+            ),
+            Chart(
+              grid: PieGrid(startAngle: 1),
+              datasets: [
+                for (final item in data.entries)
+                  PieDataSet(
+                    legend: '${item.key} ${item.value * 100 ~/ total}%',
+                    value: item.value,
+                    color: PdfColors
+                        .primaries[(color++) * 2 % PdfColors.primaries.length],
+                    innerRadius: internalRadius,
+                  ),
+              ],
+            ),
+          ],
+        ),
+      ),
+    );
+  });
+
   tearDownAll(() async {
     final file = File('widgets-chart.pdf');
     await file.writeAsBytes(await pdf.save());