Fix GridView when empty

@@ -3,11 +3,12 @@
 ## 1.5.0
 
 - Fix Align debug painting
+- Fix GridView when empty
 
 ## 1.4.1
 
 - Update dependency to barcode ^1.5.0
-- Update type1 font warning url
+- Update type1 font warning URL
 - Fix Image fit
 
 ## 1.4.0

@@ -56,10 +56,15 @@ class GridView extends MultiChildWidget implements SpanningWidget {
   @override
   void layout(Context context, BoxConstraints constraints,
       {bool parentUsesSize = false}) {
+    if (children.isEmpty) {
+      box = PdfRect.zero;
+      return;
+    }
+
     assert(() {
       if (constraints.maxHeight.isInfinite && childAspectRatio.isInfinite) {
         print(
-            'Unable to calculate the GridView dimensions. Please set one the height constraints or childAspectRatio.');
+            'Unable to calculate the GridView dimensions. Please set the height constraints or childAspectRatio.');
         return false;
       }
       return true;
@@ -208,6 +213,10 @@ class GridView extends MultiChildWidget implements SpanningWidget {
   void debugPaint(Context context) {
     super.debugPaint(context);
 
+    if (children.isEmpty) {
+      return;
+    }
+
     context.canvas
       ..setFillColor(PdfColors.lime)
       ..moveTo(box.left, box.bottom)

@@ -33,6 +33,7 @@ import 'widget_basic_test.dart' as widget_basic;
 import 'widget_clip_test.dart' as widget_clip;
 import 'widget_container_test.dart' as widget_container;
 import 'widget_flex_test.dart' as widget_flex;
+import 'widget_grid_view_test.dart' as widget_grid_view;
 import 'widget_multipage_test.dart' as widget_multipage;
 import 'widget_table_test.dart' as widget_table;
 import 'widget_test.dart' as widget;
@@ -59,6 +60,7 @@ void main() {
   widget_clip.main();
   widget_container.main();
   widget_flex.main();
+  widget_grid_view.main();
   widget_multipage.main();
   widget_table.main();
   widget_text.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.
+ */
+
+// ignore_for_file: omit_local_variable_types
+
+import 'dart:io';
+
+import 'package:pdf/widgets.dart';
+import 'package:test/test.dart';
+
+Document pdf;
+
+void main() {
+  setUpAll(() {
+    Document.debug = true;
+    pdf = Document();
+  });
+
+  test('Pdf Widgets GridView empty', () {
+    pdf.addPage(MultiPage(
+        build: (Context context) => <Widget>[
+              GridView(
+                crossAxisCount: 1,
+                childAspectRatio: 1,
+              ),
+            ]));
+  });
+
+  test('Pdf Widgets GridView Vertical', () {
+    pdf.addPage(MultiPage(
+        build: (Context context) => <Widget>[
+              GridView(
+                  crossAxisCount: 3,
+                  childAspectRatio: 1,
+                  direction: Axis.vertical,
+                  children: List<Widget>.generate(
+                      20, (int index) => Center(child: Text('$index')))),
+            ]));
+  });
+
+  test('Pdf Widgets GridView Horizontal', () {
+    pdf.addPage(Page(
+      build: (Context context) => GridView(
+          crossAxisCount: 5,
+          direction: Axis.horizontal,
+          childAspectRatio: 1,
+          children: List<Widget>.generate(
+              20, (int index) => Center(child: Text('$index')))),
+    ));
+  });
+
+  tearDownAll(() {
+    final File file = File('widgets-gridview.pdf');
+    file.writeAsBytesSync(pdf.save());
+  });
+}