Add Circular Progress Indicator

@@ -3,6 +3,7 @@
 * Remove color constants from PdfColor, use PdfColors
 * Add TTF Font SubSetting
 * Add Unicode support for TTF Fonts
+* Add Circular Progress Indicator
 
 # 1.3.4
 * Add available dimensions for PdfPageFormat

@@ -397,7 +397,7 @@ class PdfGraphics {
   /// The center (cx, cy) of the ellipse is calculated automatically to satisfy
   /// the constraints imposed by the other parameters. large and sweep flags
   /// contribute to the automatic calculations and help determine how the arc is drawn.
-  void _bezierArc(
+  void bezierArc(
       double x1, double y1, double rx, double ry, double x2, double y2,
       {bool large = false, bool sweep = false, double phi = 0.0}) {
     if (x1 == x2 && y1 == y2) {
@@ -555,7 +555,7 @@ class PdfGraphics {
           case 'A': // elliptical arc, absolute
             int len = 0;
             while (len < points.length) {
-              _bezierArc(lastPoint.x, lastPoint.y, points[len + 0],
+              bezierArc(lastPoint.x, lastPoint.y, points[len + 0],
                   points[len + 1], points[len + 5], points[len + 6],
                   phi: points[len + 2] * math.pi / 180.0,
                   large: points[len + 3] != 0.0,
@@ -569,7 +569,7 @@ class PdfGraphics {
             while (len < points.length) {
               points[len + 5] += lastPoint.x;
               points[len + 6] += lastPoint.y;
-              _bezierArc(lastPoint.x, lastPoint.y, points[len + 0],
+              bezierArc(lastPoint.x, lastPoint.y, points[len + 0],
                   points[len + 1], points[len + 5], points[len + 6],
                   phi: points[len + 2] * math.pi / 180.0,
                   large: points[len + 3] != 0.0,

@@ -36,6 +36,7 @@ part 'widgets/grid_view.dart';
 part 'widgets/image.dart';
 part 'widgets/multi_page.dart';
 part 'widgets/placeholders.dart';
+part 'widgets/progress.dart';
 part 'widgets/stack.dart';
 part 'widgets/table.dart';
 part 'widgets/text.dart';

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+part of widget;
+
+class CircularProgressIndicator extends Widget {
+  CircularProgressIndicator(
+      {@required this.value,
+      this.color,
+      this.strokeWidth = 4.0,
+      this.backgroundColor})
+      : assert(value != null),
+        assert(strokeWidth != null);
+
+  final double value;
+
+  final PdfColor color;
+
+  final PdfColor backgroundColor;
+
+  final double strokeWidth;
+
+  @override
+  void layout(Context context, BoxConstraints constraints,
+      {bool parentUsesSize = false}) {
+    box = PdfRect.fromPoints(PdfPoint.zero, constraints.biggest);
+  }
+
+  @override
+  void paint(Context context) {
+    super.paint(context);
+
+    final double adjustedValue = value.clamp(0.00001, .99999);
+    final double rx = box.width / 2;
+    final double ry = box.height / 2;
+    const double angleStart = math.pi / 2;
+    final double angleEnd = angleStart - math.pi * 2 * adjustedValue;
+    final PdfPoint startTop = PdfPoint(
+      box.x + rx + math.cos(angleStart) * rx,
+      box.y + ry + math.sin(angleStart) * ry,
+    );
+    final PdfPoint endTop = PdfPoint(
+      box.x + rx + math.cos(angleEnd) * rx,
+      box.y + ry + math.sin(angleEnd) * ry,
+    );
+    final PdfPoint startBottom = PdfPoint(
+      box.x + rx + math.cos(angleStart) * (rx - strokeWidth),
+      box.y + ry + math.sin(angleStart) * (ry - strokeWidth),
+    );
+    final PdfPoint endBottom = PdfPoint(
+      box.x + rx + math.cos(angleEnd) * (rx - strokeWidth),
+      box.y + ry + math.sin(angleEnd) * (ry - strokeWidth),
+    );
+
+    if (backgroundColor != null && value < 1) {
+      context.canvas
+        ..moveTo(startTop.x, startTop.y)
+        ..bezierArc(startTop.x, startTop.y, rx, ry, endTop.x, endTop.y,
+            large: adjustedValue < .5, sweep: true)
+        ..lineTo(endBottom.x, endBottom.y)
+        ..bezierArc(endBottom.x, endBottom.y, rx - strokeWidth,
+            ry - strokeWidth, startBottom.x, startBottom.y,
+            large: adjustedValue < .5)
+        ..lineTo(startTop.x, startTop.y)
+        ..setFillColor(backgroundColor)
+        ..fillPath();
+    }
+
+    if (value > 0) {
+      context.canvas
+        ..moveTo(startTop.x, startTop.y)
+        ..bezierArc(startTop.x, startTop.y, rx, ry, endTop.x, endTop.y,
+            large: adjustedValue > .5)
+        ..lineTo(endBottom.x, endBottom.y)
+        ..bezierArc(endBottom.x, endBottom.y, rx - strokeWidth,
+            ry - strokeWidth, startBottom.x, startBottom.y,
+            large: adjustedValue > .5, sweep: true)
+        ..lineTo(startTop.x, startTop.y)
+        ..setFillColor(color ?? PdfColors.indigo)
+        ..fillPath();
+    }
+  }
+}

@@ -182,7 +182,24 @@ void main() {
                       bottom: 10,
                       child: UrlLink(
                           child: Text('dart_pdf'),
-                          destination: 'https://github.com/DavBfr/dart_pdf/'))
+                          destination: 'https://github.com/DavBfr/dart_pdf/')),
+                  Positioned(
+                      left: 10,
+                      top: 10,
+                      child: Container(
+                          width: 100,
+                          height: 100,
+                          child: Stack(
+                              alignment: Alignment.center,
+                              fit: StackFit.expand,
+                              children: <Widget>[
+                                Center(
+                                    child: Text('30%', textScaleFactor: 1.5)),
+                                CircularProgressIndicator(
+                                    value: .3,
+                                    backgroundColor: PdfColors.grey300,
+                                    strokeWidth: 15),
+                              ])))
                 ])));
 
     final File file = File('widgets.pdf');