Add Wrap Widget

@@ -5,6 +5,7 @@
 * Add better debugPaint on Align Widget
 * Add better debugPaint on Align Widget
 * Fix Transform placement when Alignment and Origin are Null
 * Fix Transform placement when Alignment and Origin are Null
 * Add Transform.rotateBox constructor
 * Add Transform.rotateBox constructor
+* Add Wrap Widget
 
 
 ## 1.3.15
 ## 1.3.15
 
 

@@ -42,3 +42,4 @@ part 'widgets/table.dart';
 part 'widgets/text.dart';
 part 'widgets/text.dart';
 part 'widgets/theme.dart';
 part 'widgets/theme.dart';
 part 'widgets/widget.dart';
 part 'widgets/widget.dart';
+part 'widgets/wrap.dart';

@@ -46,6 +46,14 @@ class BoxConstraints {
         minHeight = height != null ? height : double.infinity,
         minHeight = height != null ? height : double.infinity,
         maxHeight = height != null ? height : double.infinity;
         maxHeight = height != null ? height : double.infinity;
 
 
+  const BoxConstraints.tightForFinite({
+    double width = double.infinity,
+    double height = double.infinity,
+  })  : minWidth = width != double.infinity ? width : 0.0,
+        maxWidth = width != double.infinity ? width : double.infinity,
+        minHeight = height != double.infinity ? height : 0.0,
+        maxHeight = height != double.infinity ? height : double.infinity;
+
   /// The minimum width that satisfies the constraints.
   /// The minimum width that satisfies the constraints.
   final double minWidth;
   final double minWidth;
 
 

+/*
+ * 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;
+
+/// How [Wrap] should align objects.
+enum WrapAlignment {
+  start,
+  end,
+  center,
+  spaceBetween,
+  spaceAround,
+  spaceEvenly
+}
+
+/// Who [Wrap] should align children within a run in the cross axis.
+enum WrapCrossAlignment { start, end, center }
+
+class _RunMetrics {
+  _RunMetrics(this.mainAxisExtent, this.crossAxisExtent, this.childCount);
+
+  final double mainAxisExtent;
+  final double crossAxisExtent;
+  final int childCount;
+}
+
+/// A widget that displays its children in multiple horizontal or vertical runs.
+class Wrap extends MultiChildWidget {
+  /// Creates a wrap layout.
+
+  Wrap({
+    this.direction = Axis.horizontal,
+    this.alignment = WrapAlignment.start,
+    this.spacing = 0.0,
+    this.runAlignment = WrapAlignment.start,
+    this.runSpacing = 0.0,
+    this.crossAxisAlignment = WrapCrossAlignment.start,
+    this.verticalDirection = VerticalDirection.down,
+    List<Widget> children = const <Widget>[],
+  })  : assert(direction != null),
+        assert(alignment != null),
+        assert(spacing != null),
+        assert(runAlignment != null),
+        assert(runSpacing != null),
+        assert(crossAxisAlignment != null),
+        super(children: children);
+
+  /// The direction to use as the main axis.
+  final Axis direction;
+
+  /// How the children within a run should be placed in the main axis.
+  final WrapAlignment alignment;
+
+  /// How much space to place between children in a run in the main axis.
+  final double spacing;
+
+  /// How the runs themselves should be placed in the cross axis.
+  final WrapAlignment runAlignment;
+
+  /// How much space to place between the runs themselves in the cross axis.
+  final double runSpacing;
+
+  /// How the children within a run should be aligned relative to each other in
+  /// the cross axis.
+  final WrapCrossAlignment crossAxisAlignment;
+
+  /// Determines the order to lay children out vertically and how to interpret
+  /// `start` and `end` in the vertical direction.
+  final VerticalDirection verticalDirection;
+
+  bool get textDirection => false;
+
+  bool _hasVisualOverflow = false;
+
+  bool get _debugHasNecessaryDirections {
+    assert(direction != null);
+    assert(alignment != null);
+    assert(runAlignment != null);
+    assert(crossAxisAlignment != null);
+    if (children.length > 1) {
+      // i.e. there's more than one child
+      switch (direction) {
+        case Axis.horizontal:
+          assert(textDirection != null,
+              'Horizontal $runtimeType with multiple children has a null textDirection, so the layout order is undefined.');
+          break;
+        case Axis.vertical:
+          assert(verticalDirection != null,
+              'Vertical $runtimeType with multiple children has a null verticalDirection, so the layout order is undefined.');
+          break;
+      }
+    }
+    if (alignment == WrapAlignment.start || alignment == WrapAlignment.end) {
+      switch (direction) {
+        case Axis.horizontal:
+          assert(textDirection != null,
+              'Horizontal $runtimeType with alignment $alignment has a null textDirection, so the alignment cannot be resolved.');
+          break;
+        case Axis.vertical:
+          assert(verticalDirection != null,
+              'Vertical $runtimeType with alignment $alignment has a null verticalDirection, so the alignment cannot be resolved.');
+          break;
+      }
+    }
+    if (runAlignment == WrapAlignment.start ||
+        runAlignment == WrapAlignment.end) {
+      switch (direction) {
+        case Axis.horizontal:
+          assert(verticalDirection != null,
+              'Horizontal $runtimeType with runAlignment $runAlignment has a null verticalDirection, so the alignment cannot be resolved.');
+          break;
+        case Axis.vertical:
+          assert(textDirection != null,
+              'Vertical $runtimeType with runAlignment $runAlignment has a null textDirection, so the alignment cannot be resolved.');
+          break;
+      }
+    }
+    if (crossAxisAlignment == WrapCrossAlignment.start ||
+        crossAxisAlignment == WrapCrossAlignment.end) {
+      switch (direction) {
+        case Axis.horizontal:
+          assert(verticalDirection != null,
+              'Horizontal $runtimeType with crossAxisAlignment $crossAxisAlignment has a null verticalDirection, so the alignment cannot be resolved.');
+          break;
+        case Axis.vertical:
+          assert(textDirection != null,
+              'Vertical $runtimeType with crossAxisAlignment $crossAxisAlignment has a null textDirection, so the alignment cannot be resolved.');
+          break;
+      }
+    }
+    return true;
+  }
+
+  double _getMainAxisExtent(Widget child) {
+    switch (direction) {
+      case Axis.horizontal:
+        return child.box.width;
+      case Axis.vertical:
+        return child.box.height;
+    }
+    return 0.0;
+  }
+
+  double _getCrossAxisExtent(Widget child) {
+    switch (direction) {
+      case Axis.horizontal:
+        return child.box.height;
+      case Axis.vertical:
+        return child.box.width;
+    }
+    return 0.0;
+  }
+
+  PdfPoint _getOffset(double mainAxisOffset, double crossAxisOffset) {
+    switch (direction) {
+      case Axis.horizontal:
+        return PdfPoint(mainAxisOffset, crossAxisOffset);
+      case Axis.vertical:
+        return PdfPoint(crossAxisOffset, mainAxisOffset);
+    }
+    return PdfPoint.zero;
+  }
+
+  double _getChildCrossAxisOffset(bool flipCrossAxis, double runCrossAxisExtent,
+      double childCrossAxisExtent) {
+    final double freeSpace = runCrossAxisExtent - childCrossAxisExtent;
+    switch (crossAxisAlignment) {
+      case WrapCrossAlignment.start:
+        return flipCrossAxis ? freeSpace : 0.0;
+      case WrapCrossAlignment.end:
+        return flipCrossAxis ? 0.0 : freeSpace;
+      case WrapCrossAlignment.center:
+        return freeSpace / 2.0;
+    }
+    return 0.0;
+  }
+
+  @override
+  void layout(Context context, BoxConstraints constraints,
+      {bool parentUsesSize = false}) {
+    assert(_debugHasNecessaryDirections);
+    _hasVisualOverflow = false;
+
+    if (children.isEmpty) {
+      box = PdfRect.fromPoints(PdfPoint.zero, constraints.smallest);
+      return;
+    }
+
+    BoxConstraints childConstraints;
+    double mainAxisLimit = 0.0;
+    bool flipMainAxis = false;
+    bool flipCrossAxis = false;
+
+    switch (direction) {
+      case Axis.horizontal:
+        childConstraints = BoxConstraints(maxWidth: constraints.maxWidth);
+        mainAxisLimit = constraints.maxWidth;
+        if (verticalDirection == VerticalDirection.down) {
+          flipCrossAxis = true;
+        }
+        break;
+      case Axis.vertical:
+        childConstraints = BoxConstraints(maxHeight: constraints.maxHeight);
+        mainAxisLimit = constraints.maxHeight;
+        if (verticalDirection == VerticalDirection.down) {
+          flipMainAxis = true;
+        }
+        break;
+    }
+
+    assert(childConstraints != null);
+    assert(mainAxisLimit != null);
+
+    final double spacing = this.spacing;
+    final double runSpacing = this.runSpacing;
+    final List<_RunMetrics> runMetrics = <_RunMetrics>[];
+    final Map<Widget, int> childRunMetrics = <Widget, int>{};
+    double mainAxisExtent = 0.0;
+    double crossAxisExtent = 0.0;
+    double runMainAxisExtent = 0.0;
+    double runCrossAxisExtent = 0.0;
+    int childCount = 0;
+
+    for (Widget child in children) {
+      child.layout(context, childConstraints, parentUsesSize: true);
+
+      final double childMainAxisExtent = _getMainAxisExtent(child);
+      final double childCrossAxisExtent = _getCrossAxisExtent(child);
+
+      if (childCount > 0 &&
+          runMainAxisExtent + spacing + childMainAxisExtent > mainAxisLimit) {
+        mainAxisExtent = math.max(mainAxisExtent, runMainAxisExtent);
+        crossAxisExtent += runCrossAxisExtent;
+        if (runMetrics.isNotEmpty) {
+          crossAxisExtent += runSpacing;
+        }
+        runMetrics.add(
+            _RunMetrics(runMainAxisExtent, runCrossAxisExtent, childCount));
+        runMainAxisExtent = 0.0;
+        runCrossAxisExtent = 0.0;
+        childCount = 0;
+      }
+
+      runMainAxisExtent += childMainAxisExtent;
+
+      if (childCount > 0) {
+        runMainAxisExtent += spacing;
+      }
+
+      runCrossAxisExtent = math.max(runCrossAxisExtent, childCrossAxisExtent);
+      childCount += 1;
+
+      childRunMetrics[child] = runMetrics.length;
+    }
+
+    if (childCount > 0) {
+      mainAxisExtent = math.max(mainAxisExtent, runMainAxisExtent);
+      crossAxisExtent += runCrossAxisExtent;
+      if (runMetrics.isNotEmpty) {
+        crossAxisExtent += runSpacing;
+      }
+      runMetrics
+          .add(_RunMetrics(runMainAxisExtent, runCrossAxisExtent, childCount));
+    }
+
+    final int runCount = runMetrics.length;
+    assert(runCount > 0);
+
+    double containerMainAxisExtent = 0.0;
+    double containerCrossAxisExtent = 0.0;
+
+    switch (direction) {
+      case Axis.horizontal:
+        box = PdfRect.fromPoints(PdfPoint.zero,
+            constraints.constrain(PdfPoint(mainAxisExtent, crossAxisExtent)));
+        containerMainAxisExtent = box.width;
+        containerCrossAxisExtent = box.height;
+        break;
+      case Axis.vertical:
+        box = PdfRect.fromPoints(PdfPoint.zero,
+            constraints.constrain(PdfPoint(crossAxisExtent, mainAxisExtent)));
+        containerMainAxisExtent = box.height;
+        containerCrossAxisExtent = box.width;
+        break;
+    }
+
+    _hasVisualOverflow = containerMainAxisExtent < mainAxisExtent ||
+        containerCrossAxisExtent < crossAxisExtent;
+
+    final double crossAxisFreeSpace =
+        math.max(0.0, containerCrossAxisExtent - crossAxisExtent);
+    double runLeadingSpace = 0.0;
+    double runBetweenSpace = 0.0;
+
+    switch (runAlignment) {
+      case WrapAlignment.start:
+        break;
+      case WrapAlignment.end:
+        runLeadingSpace = crossAxisFreeSpace;
+        break;
+      case WrapAlignment.center:
+        runLeadingSpace = crossAxisFreeSpace / 2.0;
+        break;
+      case WrapAlignment.spaceBetween:
+        runBetweenSpace =
+            runCount > 1 ? crossAxisFreeSpace / (runCount - 1) : 0.0;
+        break;
+      case WrapAlignment.spaceAround:
+        runBetweenSpace = crossAxisFreeSpace / runCount;
+        runLeadingSpace = runBetweenSpace / 2.0;
+        break;
+      case WrapAlignment.spaceEvenly:
+        runBetweenSpace = crossAxisFreeSpace / (runCount + 1);
+        runLeadingSpace = runBetweenSpace;
+        break;
+    }
+
+    runBetweenSpace += runSpacing;
+    double crossAxisOffset = flipCrossAxis
+        ? containerCrossAxisExtent - runLeadingSpace
+        : runLeadingSpace;
+
+    int currentWidget = 0;
+    for (int i = 0; i < runCount; ++i) {
+      final _RunMetrics metrics = runMetrics[i];
+      final double runMainAxisExtent = metrics.mainAxisExtent;
+      final double runCrossAxisExtent = metrics.crossAxisExtent;
+      final int childCount = metrics.childCount;
+
+      final double mainAxisFreeSpace =
+          math.max(0.0, containerMainAxisExtent - runMainAxisExtent);
+      double childLeadingSpace = 0.0;
+      double childBetweenSpace = 0.0;
+
+      switch (alignment) {
+        case WrapAlignment.start:
+          break;
+        case WrapAlignment.end:
+          childLeadingSpace = mainAxisFreeSpace;
+          break;
+        case WrapAlignment.center:
+          childLeadingSpace = mainAxisFreeSpace / 2.0;
+          break;
+        case WrapAlignment.spaceBetween:
+          childBetweenSpace =
+              childCount > 1 ? mainAxisFreeSpace / (childCount - 1) : 0.0;
+          break;
+        case WrapAlignment.spaceAround:
+          childBetweenSpace = mainAxisFreeSpace / childCount;
+          childLeadingSpace = childBetweenSpace / 2.0;
+          break;
+        case WrapAlignment.spaceEvenly:
+          childBetweenSpace = mainAxisFreeSpace / (childCount + 1);
+          childLeadingSpace = childBetweenSpace;
+          break;
+      }
+
+      childBetweenSpace += spacing;
+      double childMainPosition = flipMainAxis
+          ? containerMainAxisExtent - childLeadingSpace
+          : childLeadingSpace;
+
+      if (flipCrossAxis) {
+        crossAxisOffset -= runCrossAxisExtent;
+      }
+
+      for (Widget child in children.sublist(currentWidget)) {
+        final int runIndex = childRunMetrics[child];
+        if (runIndex != i) {
+          break;
+        }
+
+        currentWidget++;
+        final double childMainAxisExtent = _getMainAxisExtent(child);
+        final double childCrossAxisExtent = _getCrossAxisExtent(child);
+        final double childCrossAxisOffset = _getChildCrossAxisOffset(
+            flipCrossAxis, runCrossAxisExtent, childCrossAxisExtent);
+        if (flipMainAxis) {
+          childMainPosition -= childMainAxisExtent;
+        }
+        child.box = PdfRect.fromPoints(
+            _getOffset(
+                childMainPosition, crossAxisOffset + childCrossAxisOffset),
+            child.box.size);
+        if (flipMainAxis) {
+          childMainPosition -= childBetweenSpace;
+        } else {
+          childMainPosition += childMainAxisExtent + childBetweenSpace;
+        }
+      }
+
+      if (flipCrossAxis) {
+        crossAxisOffset -= runBetweenSpace;
+      } else {
+        crossAxisOffset += runCrossAxisExtent + runBetweenSpace;
+      }
+    }
+  }
+
+  @override
+  void paint(Context context) {
+    super.paint(context);
+
+    context.canvas.saveContext();
+
+    if (_hasVisualOverflow) {
+      context.canvas
+        ..drawRect(box.left, box.bottom, box.width, box.height)
+        ..clipPath();
+    }
+
+    final Matrix4 mat = Matrix4.identity();
+    mat.translate(box.x, box.y);
+    context.canvas.setTransform(mat);
+    for (Widget child in children) {
+      child.paint(context);
+    }
+
+    context.canvas.restoreContext();
+  }
+}

@@ -32,6 +32,7 @@ import 'widget_table_test.dart' as widget_table;
 import 'widget_test.dart' as widget;
 import 'widget_test.dart' as widget;
 import 'widget_text_test.dart' as widget_text;
 import 'widget_text_test.dart' as widget_text;
 import 'widget_theme_test.dart' as widget_theme;
 import 'widget_theme_test.dart' as widget_theme;
+import 'widget_wrap_test.dart' as widget_wrap;
 
 
 void main() {
 void main() {
   annotations.main();
   annotations.main();
@@ -49,5 +50,6 @@ void main() {
   widget_table.main();
   widget_table.main();
   widget_text.main();
   widget_text.main();
   widget_theme.main();
   widget_theme.main();
+  widget_wrap.main();
   widget.main();
   widget.main();
 }
 }

+/*
+ * 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.
+ */
+
+import 'dart:io';
+import 'dart:math' as math;
+
+import 'package:test/test.dart';
+import 'package:pdf/pdf.dart';
+import 'package:pdf/widgets.dart';
+
+Document pdf;
+
+void main() {
+  setUpAll(() {
+    Document.debug = true;
+    pdf = Document();
+  });
+
+  test('Wrap Widget Horizontal 1', () {
+    final List<Widget> wraps = <Widget>[];
+    for (VerticalDirection direction in VerticalDirection.values) {
+      wraps.add(Text('$direction'));
+      for (WrapAlignment alignment in WrapAlignment.values) {
+        wraps.add(Text('$alignment'));
+        wraps.add(
+          Wrap(
+            direction: Axis.horizontal,
+            verticalDirection: direction,
+            alignment: alignment,
+            children: List<Widget>.generate(
+              40,
+              (int n) => Text('${n + 1}'),
+            ),
+          ),
+        );
+      }
+    }
+
+    pdf.addPage(
+      Page(
+        pageFormat: const PdfPageFormat(400, 800),
+        margin: const EdgeInsets.all(10),
+        build: (Context context) => Column(
+          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+          children: wraps,
+        ),
+      ),
+    );
+  });
+
+  test('Wrap Widget Vertical 1', () {
+    final List<Widget> wraps = <Widget>[];
+    for (VerticalDirection direction in VerticalDirection.values) {
+      wraps.add(Transform.rotateBox(child: Text('$direction'), angle: 1.57));
+      for (WrapAlignment alignment in WrapAlignment.values) {
+        wraps.add(Transform.rotateBox(child: Text('$alignment'), angle: 1.57));
+        wraps.add(
+          Wrap(
+            direction: Axis.vertical,
+            verticalDirection: direction,
+            alignment: alignment,
+            children: List<Widget>.generate(
+              40,
+              (int n) => Text('${n + 1}'),
+            ),
+          ),
+        );
+      }
+    }
+
+    pdf.addPage(
+      Page(
+        pageFormat: const PdfPageFormat(800, 400),
+        margin: const EdgeInsets.all(10),
+        build: (Context context) => Row(
+          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+          children: wraps,
+        ),
+      ),
+    );
+  });
+
+  test('Wrap Widget Horizontal 2', () {
+    final List<Widget> wraps = <Widget>[];
+    for (WrapCrossAlignment alignment in WrapCrossAlignment.values) {
+      final math.Random rnd = math.Random(42);
+      wraps.add(Text('$alignment'));
+      wraps.add(
+        Wrap(
+          direction: Axis.horizontal,
+          crossAxisAlignment: alignment,
+          runSpacing: 20,
+          spacing: 20,
+          children: List<Widget>.generate(
+              20,
+              (int n) => SizedBox(
+                    width: rnd.nextDouble() * 100,
+                    height: rnd.nextDouble() * 50,
+                    child: Placeholder(),
+                  )),
+        ),
+      );
+    }
+
+    pdf.addPage(
+      Page(
+        pageFormat: const PdfPageFormat(400, 800),
+        margin: const EdgeInsets.all(10),
+        build: (Context context) => Column(
+          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+          children: wraps,
+        ),
+      ),
+    );
+  });
+
+  test('Wrap Widget Vertical 2', () {
+    final List<Widget> wraps = <Widget>[];
+    for (WrapCrossAlignment alignment in WrapCrossAlignment.values) {
+      final math.Random rnd = math.Random(42);
+      wraps.add(Transform.rotateBox(child: Text('$alignment'), angle: 1.57));
+      wraps.add(
+        Wrap(
+          direction: Axis.vertical,
+          crossAxisAlignment: alignment,
+          runSpacing: 20,
+          spacing: 20,
+          children: List<Widget>.generate(
+              20,
+              (int n) => SizedBox(
+                    width: rnd.nextDouble() * 50,
+                    height: rnd.nextDouble() * 100,
+                    child: Placeholder(),
+                  )),
+        ),
+      );
+    }
+
+    pdf.addPage(
+      Page(
+        pageFormat: const PdfPageFormat(800, 400),
+        margin: const EdgeInsets.all(10),
+        build: (Context context) => Row(
+          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+          children: wraps,
+        ),
+      ),
+    );
+  });
+
+  test('Wrap Widget Horizontal 3', () {
+    final List<Widget> wraps = <Widget>[];
+    for (WrapAlignment alignment in WrapAlignment.values) {
+      final math.Random rnd = math.Random(42);
+      wraps.add(Text('$alignment'));
+      wraps.add(
+        SizedBox(
+          height: 110,
+          child: Wrap(
+            direction: Axis.horizontal,
+            runAlignment: alignment,
+            spacing: 20,
+            children: List<Widget>.generate(
+                15,
+                (int n) => SizedBox(
+                      width: rnd.nextDouble() * 100,
+                      height: 20,
+                      child: Placeholder(),
+                    )),
+          ),
+        ),
+      );
+    }
+
+    pdf.addPage(
+      Page(
+        pageFormat: const PdfPageFormat(400, 800),
+        margin: const EdgeInsets.all(10),
+        build: (Context context) => Column(
+          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+          children: wraps,
+        ),
+      ),
+    );
+  });
+
+  test('Wrap Widget Vertical 3', () {
+    final List<Widget> wraps = <Widget>[];
+    for (WrapAlignment alignment in WrapAlignment.values) {
+      final math.Random rnd = math.Random(42);
+      wraps.add(Transform.rotateBox(child: Text('$alignment'), angle: 1.57));
+      wraps.add(
+        SizedBox(
+          width: 110,
+          child: Wrap(
+            direction: Axis.vertical,
+            runAlignment: alignment,
+            spacing: 20,
+            children: List<Widget>.generate(
+                15,
+                (int n) => SizedBox(
+                      width: 20,
+                      height: rnd.nextDouble() * 100,
+                      child: Placeholder(),
+                    )),
+          ),
+        ),
+      );
+    }
+
+    pdf.addPage(
+      Page(
+        pageFormat: const PdfPageFormat(800, 400),
+        margin: const EdgeInsets.all(10),
+        build: (Context context) => Row(
+          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+          children: wraps,
+        ),
+      ),
+    );
+  });
+
+  test('Wrap Widget Overlay', () {
+    final math.Random rnd = math.Random(42);
+    pdf.addPage(
+      Page(
+        pageFormat: const PdfPageFormat(200, 200),
+        margin: const EdgeInsets.all(10),
+        build: (Context context) => Wrap(
+          spacing: 10,
+          runSpacing: 10,
+          children: List<Widget>.generate(
+              15,
+              (int n) => SizedBox(
+                    width: rnd.nextDouble() * 100,
+                    height: rnd.nextDouble() * 100,
+                    child: Placeholder(),
+                  )),
+        ),
+      ),
+    );
+  });
+
+  test('Wrap Widget Empty', () {
+    pdf.addPage(Page(build: (Context context) => Wrap()));
+  });
+
+  tearDownAll(() {
+    final File file = File('widgets-wrap.pdf');
+    file.writeAsBytesSync(pdf.save());
+  });
+}