DataTable Custom Horizontal Padding (#33628)

* Add optional horizontalMargin and columnSpacing properties to DataTable

* Add horizontalMargin and columnSpacing tests for DataTable and PaginatedDataTable

packages/flutter/lib/src/material/data_table.dart

@@ -262,11 +262,15 @@ class DataTable extends StatelessWidget {
     this.sortColumnIndex,
     this.sortAscending = true,
     this.onSelectAll,
+    this.horizontalMargin = 24.0,
+    this.columnSpacing = 56.0,
     @required this.rows,
   }) : assert(columns != null),
        assert(columns.isNotEmpty),
        assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length)),
        assert(sortAscending != null),
+       assert(horizontalMargin != null),
+       assert(columnSpacing != null),
        assert(rows != null),
        assert(!rows.any((DataRow row) => row.cells.length != columns.length)),
        _onlyTextColumn = _initOnlyTextColumn(columns),
@@ -311,6 +315,20 @@ class DataTable extends StatelessWidget {
   /// row is selectable.
   final ValueSetter<bool> onSelectAll;
 
+  /// The horizontal margin between the edges of the table and the content
+  /// in the first and last cells of each row.
+  ///
+  /// When a checkbox is displayed, it is also the margin between the checkbox
+  /// the content in the first data column.
+  ///
+  /// This value defaults to 24.0 to adhere to the Material Design specifications.
+  final double horizontalMargin;
+
+  /// The horizontal margin between the contents of each data column.
+  ///
+  /// This value defaults to 56.0 to adhere to the Material Design specifications.
+  final double columnSpacing;
+
   /// The data to show in each row (excluding the row that contains
   /// the column headings). Must be non-null, but may be empty.
   final List<DataRow> rows;
@@ -351,8 +369,6 @@ class DataTable extends StatelessWidget {
 
   static const double _headingRowHeight = 56.0;
   static const double _dataRowHeight = 48.0;
-  static const double _tablePadding = 24.0;
-  static const double _columnSpacing = 56.0;
   static const double _sortArrowPadding = 2.0;
   static const double _headingFontSize = 12.0;
   static const Duration _sortArrowAnimationDuration = Duration(milliseconds: 150);
@@ -368,7 +384,7 @@ class DataTable extends StatelessWidget {
     Widget contents = Semantics(
       container: true,
       child: Padding(
-        padding: const EdgeInsetsDirectional.only(start: _tablePadding, end: _tablePadding / 2.0),
+        padding: EdgeInsetsDirectional.only(start: horizontalMargin, end: horizontalMargin / 2.0),
         child: Center(
           child: Checkbox(
             activeColor: color,
@@ -533,7 +549,7 @@ class DataTable extends StatelessWidget {
 
     int displayColumnIndex = 0;
     if (showCheckboxColumn) {
-      tableColumns[0] = const FixedColumnWidth(_tablePadding + Checkbox.width + _tablePadding / 2.0);
+      tableColumns[0] = FixedColumnWidth(horizontalMargin + Checkbox.width + horizontalMargin / 2.0);
       tableRows[0].children[0] = _buildCheckbox(
         color: theme.accentColor,
         checked: allChecked,
@@ -554,9 +570,26 @@ class DataTable extends StatelessWidget {
 
     for (int dataColumnIndex = 0; dataColumnIndex < columns.length; dataColumnIndex += 1) {
       final DataColumn column = columns[dataColumnIndex];
+
+      double paddingStart;
+      if (dataColumnIndex == 0 && showCheckboxColumn) {
+        paddingStart = horizontalMargin / 2.0;
+      } else if (dataColumnIndex == 0 && !showCheckboxColumn) {
+        paddingStart = horizontalMargin;
+      } else {
+        paddingStart = columnSpacing / 2.0;
+      }
+
+      double paddingEnd;
+      if (dataColumnIndex == columns.length - 1) {
+        paddingEnd = horizontalMargin;
+      } else {
+        paddingEnd = columnSpacing / 2.0;
+      }
+
       final EdgeInsetsDirectional padding = EdgeInsetsDirectional.only(
-        start: dataColumnIndex == 0 ? showCheckboxColumn ? _tablePadding / 2.0 : _tablePadding : _columnSpacing / 2.0,
-        end: dataColumnIndex == columns.length - 1 ? _tablePadding : _columnSpacing / 2.0,
+        start: paddingStart,
+        end: paddingEnd,
       );
       if (dataColumnIndex == _onlyTextColumn) {
         tableColumns[displayColumnIndex] = const IntrinsicColumnWidth(flex: 1.0);

packages/flutter/lib/src/material/paginated_data_table.dart

@@ -70,6 +70,8 @@ class PaginatedDataTable extends StatefulWidget {
     this.sortColumnIndex,
     this.sortAscending = true,
     this.onSelectAll,
+    this.horizontalMargin = 24.0,
+    this.columnSpacing = 56.0,
     this.initialFirstRowIndex = 0,
     this.onPageChanged,
     this.rowsPerPage = defaultRowsPerPage,
@@ -83,6 +85,8 @@ class PaginatedDataTable extends StatefulWidget {
        assert(columns.isNotEmpty),
        assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length)),
        assert(sortAscending != null),
+       assert(horizontalMargin != null),
+       assert(columnSpacing != null),
        assert(rowsPerPage != null),
        assert(rowsPerPage > 0),
        assert(() {
@@ -131,6 +135,20 @@ class PaginatedDataTable extends StatefulWidget {
   /// See [DataTable.onSelectAll].
   final ValueSetter<bool> onSelectAll;
 
+  /// The horizontal margin between the edges of the table and the content
+  /// in the first and last cells of each row.
+  ///
+  /// When a checkbox is displayed, it is also the margin between the checkbox
+  /// the content in the first data column.
+  ///
+  /// This value defaults to 24.0 to adhere to the Material Design specifications.
+  final double horizontalMargin;
+
+  /// The horizontal margin between the contents of each data column.
+  ///
+  /// This value defaults to 56.0 to adhere to the Material Design specifications.
+  final double columnSpacing;
+
   /// The index of the first row to display when the widget is first created.
   final int initialFirstRowIndex;
 
@@ -430,6 +448,8 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
               sortColumnIndex: widget.sortColumnIndex,
               sortAscending: widget.sortAscending,
               onSelectAll: widget.onSelectAll,
+              horizontalMargin: widget.horizontalMargin,
+              columnSpacing: widget.columnSpacing,
               rows: _getRows(_firstRowIndex, widget.rowsPerPage),
             ),
           ),

packages/flutter/test/material/data_table_test.dart

@@ -267,4 +267,420 @@ void main() {
     expect(tester.takeException(), isNull);
   });
 
+  testWidgets('DataTable custom horizontal padding - checkbox', (WidgetTester tester) async {
+    const double _defaultHorizontalMargin = 24.0;
+    const double _defaultColumnSpacing = 56.0;
+    const double _customHorizontalMargin = 10.0;
+    const double _customColumnSpacing = 15.0;
+    Finder cellContent;
+    Finder checkbox;
+    Finder padding;
+
+    Widget buildDefaultTable({
+      int sortColumnIndex,
+      bool sortAscending = true,
+    }) {
+      return DataTable(
+        sortColumnIndex: sortColumnIndex,
+        sortAscending: sortAscending,
+        onSelectAll: (bool value) {},
+        columns: <DataColumn>[
+          const DataColumn(
+            label: Text('Name'),
+            tooltip: 'Name',
+          ),
+          DataColumn(
+            label: const Text('Calories'),
+            tooltip: 'Calories',
+            numeric: true,
+            onSort: (int columnIndex, bool ascending) {},
+          ),
+          DataColumn(
+            label: const Text('Fat'),
+            tooltip: 'Fat',
+            numeric: true,
+            onSort: (int columnIndex, bool ascending) {},
+          ),
+        ],
+        rows: kDesserts.map<DataRow>((Dessert dessert) {
+          return DataRow(
+            key: Key(dessert.name),
+            onSelectChanged: (bool selected) {},
+            cells: <DataCell>[
+              DataCell(
+                Text(dessert.name),
+              ),
+              DataCell(
+                Text('${dessert.calories}'),
+                showEditIcon: true,
+                onTap: () {},
+              ),
+              DataCell(
+                Text('${dessert.fat}'),
+                showEditIcon: true,
+                onTap: () {},
+              ),
+            ],
+          );
+        }).toList(),
+      );
+    }
+
+    // DEFAULT VALUES
+    await tester.pumpWidget(MaterialApp(
+      home: Material(child: buildDefaultTable()),
+    ));
+
+    // default checkbox padding
+    checkbox = find.byType(Checkbox).first;
+    padding = find.ancestor(of: checkbox, matching: find.byType(Padding));
+    expect(
+      tester.getRect(checkbox).left - tester.getRect(padding).left,
+      _defaultHorizontalMargin,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(checkbox).right,
+      _defaultHorizontalMargin / 2,
+    );
+
+    // default first column padding
+    padding = find.widgetWithText(Padding, 'Frozen yogurt');
+    cellContent = find.widgetWithText(Align, 'Frozen yogurt'); // DataTable wraps its DataCells in an Align widget
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultHorizontalMargin / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultColumnSpacing / 2,
+    );
+
+    // default middle column padding
+    padding = find.widgetWithText(Padding, '159');
+    cellContent = find.widgetWithText(Align, '159');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultColumnSpacing / 2,
+    );
+
+    // default last column padding
+    padding = find.widgetWithText(Padding, '6.0');
+    cellContent = find.widgetWithText(Align, '6.0');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultHorizontalMargin,
+    );
+
+    Widget buildCustomTable({
+      int sortColumnIndex,
+      bool sortAscending = true,
+      double horizontalMargin,
+      double columnSpacing,
+    }) {
+      return DataTable(
+        sortColumnIndex: sortColumnIndex,
+        sortAscending: sortAscending,
+        onSelectAll: (bool value) {},
+        horizontalMargin: horizontalMargin,
+        columnSpacing: columnSpacing,
+        columns: <DataColumn>[
+          const DataColumn(
+            label: Text('Name'),
+            tooltip: 'Name',
+          ),
+          DataColumn(
+            label: const Text('Calories'),
+            tooltip: 'Calories',
+            numeric: true,
+            onSort: (int columnIndex, bool ascending) {},
+          ),
+          DataColumn(
+            label: const Text('Fat'),
+            tooltip: 'Fat',
+            numeric: true,
+            onSort: (int columnIndex, bool ascending) {},
+          ),
+        ],
+        rows: kDesserts.map<DataRow>((Dessert dessert) {
+          return DataRow(
+            key: Key(dessert.name),
+            onSelectChanged: (bool selected) {},
+            cells: <DataCell>[
+              DataCell(
+                Text(dessert.name),
+              ),
+              DataCell(
+                Text('${dessert.calories}'),
+                showEditIcon: true,
+                onTap: () {},
+              ),
+              DataCell(
+                Text('${dessert.fat}'),
+                showEditIcon: true,
+                onTap: () {},
+              ),
+            ],
+          );
+        }).toList(),
+      );
+    }
+
+    // CUSTOM VALUES
+    await tester.pumpWidget(MaterialApp(
+      home: Material(child: buildCustomTable(
+        horizontalMargin: _customHorizontalMargin,
+        columnSpacing: _customColumnSpacing,
+      )),
+    ));
+
+    // custom checkbox padding
+    checkbox = find.byType(Checkbox).first;
+    padding = find.ancestor(of: checkbox, matching: find.byType(Padding));
+    expect(
+      tester.getRect(checkbox).left - tester.getRect(padding).left,
+      _customHorizontalMargin,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(checkbox).right,
+      _customHorizontalMargin / 2,
+    );
+
+    // custom first column padding
+    padding = find.widgetWithText(Padding, 'Frozen yogurt');
+    cellContent = find.widgetWithText(Align, 'Frozen yogurt'); // DataTable wraps its DataCells in an Align widget
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customHorizontalMargin / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customColumnSpacing / 2,
+    );
+
+    // custom middle column padding
+    padding = find.widgetWithText(Padding, '159');
+    cellContent = find.widgetWithText(Align, '159');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customColumnSpacing / 2,
+    );
+
+    // custom last column padding
+    padding = find.widgetWithText(Padding, '6.0');
+    cellContent = find.widgetWithText(Align, '6.0');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customHorizontalMargin,
+    );
+  });
+
+  testWidgets('DataTable custom horizontal padding - no checkbox', (WidgetTester tester) async {
+    const double _defaultHorizontalMargin = 24.0;
+    const double _defaultColumnSpacing = 56.0;
+    const double _customHorizontalMargin = 10.0;
+    const double _customColumnSpacing = 15.0;
+    Finder cellContent;
+    Finder padding;
+
+    Widget buildDefaultTable({
+      int sortColumnIndex,
+      bool sortAscending = true,
+    }) {
+      return DataTable(
+        sortColumnIndex: sortColumnIndex,
+        sortAscending: sortAscending,
+        columns: <DataColumn>[
+          const DataColumn(
+            label: Text('Name'),
+            tooltip: 'Name',
+          ),
+          DataColumn(
+            label: const Text('Calories'),
+            tooltip: 'Calories',
+            numeric: true,
+            onSort: (int columnIndex, bool ascending) {},
+          ),
+          DataColumn(
+            label: const Text('Fat'),
+            tooltip: 'Fat',
+            numeric: true,
+            onSort: (int columnIndex, bool ascending) {},
+          ),
+        ],
+        rows: kDesserts.map<DataRow>((Dessert dessert) {
+          return DataRow(
+            key: Key(dessert.name),
+            cells: <DataCell>[
+              DataCell(
+                Text(dessert.name),
+              ),
+              DataCell(
+                Text('${dessert.calories}'),
+                showEditIcon: true,
+                onTap: () {},
+              ),
+              DataCell(
+                Text('${dessert.fat}'),
+                showEditIcon: true,
+                onTap: () {},
+              ),
+            ],
+          );
+        }).toList(),
+      );
+    }
+
+    // DEFAULT VALUES
+    await tester.pumpWidget(MaterialApp(
+      home: Material(child: buildDefaultTable()),
+    ));
+
+    // default first column padding
+    padding = find.widgetWithText(Padding, 'Frozen yogurt');
+    cellContent = find.widgetWithText(Align, 'Frozen yogurt'); // DataTable wraps its DataCells in an Align widget
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultHorizontalMargin,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultColumnSpacing / 2,
+    );
+
+    // default middle column padding
+    padding = find.widgetWithText(Padding, '159');
+    cellContent = find.widgetWithText(Align, '159');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultColumnSpacing / 2,
+    );
+
+    // default last column padding
+    padding = find.widgetWithText(Padding, '6.0');
+    cellContent = find.widgetWithText(Align, '6.0');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultHorizontalMargin,
+    );
+
+    Widget buildCustomTable({
+      int sortColumnIndex,
+      bool sortAscending = true,
+      double horizontalMargin,
+      double columnSpacing,
+    }) {
+      return DataTable(
+        sortColumnIndex: sortColumnIndex,
+        sortAscending: sortAscending,
+        horizontalMargin: horizontalMargin,
+        columnSpacing: columnSpacing,
+        columns: <DataColumn>[
+          const DataColumn(
+            label: Text('Name'),
+            tooltip: 'Name',
+          ),
+          DataColumn(
+            label: const Text('Calories'),
+            tooltip: 'Calories',
+            numeric: true,
+            onSort: (int columnIndex, bool ascending) {},
+          ),
+          DataColumn(
+            label: const Text('Fat'),
+            tooltip: 'Fat',
+            numeric: true,
+            onSort: (int columnIndex, bool ascending) {},
+          ),
+        ],
+        rows: kDesserts.map<DataRow>((Dessert dessert) {
+          return DataRow(
+            key: Key(dessert.name),
+            cells: <DataCell>[
+              DataCell(
+                Text(dessert.name),
+              ),
+              DataCell(
+                Text('${dessert.calories}'),
+                showEditIcon: true,
+                onTap: () {},
+              ),
+              DataCell(
+                Text('${dessert.fat}'),
+                showEditIcon: true,
+                onTap: () {},
+              ),
+            ],
+          );
+        }).toList(),
+      );
+    }
+
+    // CUSTOM VALUES
+    await tester.pumpWidget(MaterialApp(
+      home: Material(child: buildCustomTable(
+        horizontalMargin: _customHorizontalMargin,
+        columnSpacing: _customColumnSpacing,
+      )),
+    ));
+
+    // custom first column padding
+    padding = find.widgetWithText(Padding, 'Frozen yogurt');
+    cellContent = find.widgetWithText(Align, 'Frozen yogurt'); // DataTable wraps its DataCells in an Align widget
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customHorizontalMargin,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customColumnSpacing / 2,
+    );
+
+    // custom middle column padding
+    padding = find.widgetWithText(Padding, '159');
+    cellContent = find.widgetWithText(Align, '159');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customColumnSpacing / 2,
+    );
+
+    // custom last column padding
+    padding = find.widgetWithText(Padding, '6.0');
+    cellContent = find.widgetWithText(Align, '6.0');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customHorizontalMargin,
+    );
+  });
 }

packages/flutter/test/material/paginated_data_table_test.dart

@@ -9,6 +9,12 @@ import 'package:flutter/gestures.dart' show DragStartBehavior;
 import 'data_table_test_utils.dart';
 
 class TestDataSource extends DataTableSource {
+  TestDataSource({
+    this.onSelectChanged,
+  });
+
+  final Function onSelectChanged;
+
   int get generation => _generation;
   int _generation = 0;
   set generation(int value) {
@@ -29,6 +35,7 @@ class TestDataSource extends DataTableSource {
         DataCell(Text('${dessert.calories}')),
         DataCell(Text('$generation')),
       ],
+      onSelectChanged: onSelectChanged,
     );
   }
 
@@ -289,4 +296,279 @@ void main() {
     expect(find.text('Rows per page:'), findsOneWidget);
     expect(tester.getTopLeft(find.text('Rows per page:')).dx, 18.0); // 14 padding in the footer row, 4 padding from the card
   });
+
+  testWidgets('PaginatedDataTable custom horizontal padding - checkbox', (WidgetTester tester) async {
+    const double _defaultHorizontalMargin = 24.0;
+    const double _defaultColumnSpacing = 56.0;
+    const double _customHorizontalMargin = 10.0;
+    const double _customColumnSpacing = 15.0;
+    final TestDataSource source = TestDataSource(
+      onSelectChanged: (bool value) {},
+    );
+    Finder cellContent;
+    Finder checkbox;
+    Finder padding;
+
+    await tester.pumpWidget(MaterialApp(
+      home: PaginatedDataTable(
+        header: const Text('Test table'),
+        source: source,
+        rowsPerPage: 2,
+        availableRowsPerPage: const <int>[
+          2, 4,
+        ],
+        onRowsPerPageChanged: (int rowsPerPage) {},
+        onPageChanged: (int rowIndex) {},
+        onSelectAll: (bool value) {},
+        columns: const <DataColumn>[
+          DataColumn(label: Text('Name')),
+          DataColumn(label: Text('Calories'), numeric: true),
+          DataColumn(label: Text('Generation')),
+        ],
+      ),
+    ));
+
+    // default checkbox padding
+    checkbox = find.byType(Checkbox).first;
+    padding = find.ancestor(of: checkbox, matching: find.byType(Padding)).first;
+    expect(
+      tester.getRect(checkbox).left - tester.getRect(padding).left,
+      _defaultHorizontalMargin,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(checkbox).right,
+      _defaultHorizontalMargin / 2,
+    );
+
+    // default first column padding
+    padding = find.widgetWithText(Padding, 'Frozen yogurt (0)').first;
+    cellContent = find.widgetWithText(Align, 'Frozen yogurt (0)'); // DataTable wraps its DataCells in an Align widget
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultHorizontalMargin / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultColumnSpacing / 2,
+    );
+
+    // default middle column padding
+    padding = find.widgetWithText(Padding, '159').first;
+    cellContent = find.widgetWithText(Align, '159');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultColumnSpacing / 2,
+    );
+
+    // default last column padding
+    padding = find.widgetWithText(Padding, '0').first;
+    cellContent = find.widgetWithText(Align, '0').first;
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultHorizontalMargin,
+    );
+
+    // CUSTOM VALUES
+    await tester.pumpWidget(MaterialApp(
+      home: Material(
+        child: PaginatedDataTable(
+          header: const Text('Test table'),
+          source: source,
+          rowsPerPage: 2,
+          availableRowsPerPage: const <int>[
+            2, 4,
+          ],
+          onRowsPerPageChanged: (int rowsPerPage) {},
+          onPageChanged: (int rowIndex) {},
+          onSelectAll: (bool value) {},
+          columns: const <DataColumn>[
+            DataColumn(label: Text('Name')),
+            DataColumn(label: Text('Calories'), numeric: true),
+            DataColumn(label: Text('Generation')),
+          ],
+          horizontalMargin: _customHorizontalMargin,
+          columnSpacing: _customColumnSpacing,
+        ),
+      ),
+    ));
+
+    // custom checkbox padding
+    checkbox = find.byType(Checkbox).first;
+    padding = find.ancestor(of: checkbox, matching: find.byType(Padding)).first;
+    expect(
+      tester.getRect(checkbox).left - tester.getRect(padding).left,
+      _customHorizontalMargin,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(checkbox).right,
+      _customHorizontalMargin / 2,
+    );
+
+    // custom first column padding
+    padding = find.widgetWithText(Padding, 'Frozen yogurt (0)').first;
+    cellContent = find.widgetWithText(Align, 'Frozen yogurt (0)'); // DataTable wraps its DataCells in an Align widget
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customHorizontalMargin / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customColumnSpacing / 2,
+    );
+
+    // custom middle column padding
+    padding = find.widgetWithText(Padding, '159').first;
+    cellContent = find.widgetWithText(Align, '159');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customColumnSpacing / 2,
+    );
+
+    // custom last column padding
+    padding = find.widgetWithText(Padding, '0').first;
+    cellContent = find.widgetWithText(Align, '0').first;
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customHorizontalMargin,
+    );
+  });
+
+  testWidgets('PaginatedDataTable custom horizontal padding - no checkbox', (WidgetTester tester) async {
+    const double _defaultHorizontalMargin = 24.0;
+    const double _defaultColumnSpacing = 56.0;
+    const double _customHorizontalMargin = 10.0;
+    const double _customColumnSpacing = 15.0;
+    final TestDataSource source = TestDataSource();
+    Finder cellContent;
+    Finder padding;
+
+    await tester.pumpWidget(MaterialApp(
+      home: PaginatedDataTable(
+        header: const Text('Test table'),
+        source: source,
+        rowsPerPage: 2,
+        availableRowsPerPage: const <int>[
+          2, 4, 8, 16,
+        ],
+        onRowsPerPageChanged: (int rowsPerPage) {},
+        onPageChanged: (int rowIndex) {},
+        columns: const <DataColumn>[
+          DataColumn(label: Text('Name')),
+          DataColumn(label: Text('Calories'), numeric: true),
+          DataColumn(label: Text('Generation')),
+        ],
+      ),
+    ));
+
+    // default first column padding
+    padding = find.widgetWithText(Padding, 'Frozen yogurt (0)').first;
+    cellContent = find.widgetWithText(Align, 'Frozen yogurt (0)'); // DataTable wraps its DataCells in an Align widget
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultHorizontalMargin,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultColumnSpacing / 2,
+    );
+
+    // default middle column padding
+    padding = find.widgetWithText(Padding, '159').first;
+    cellContent = find.widgetWithText(Align, '159');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultColumnSpacing / 2,
+    );
+
+    // default last column padding
+    padding = find.widgetWithText(Padding, '0').first;
+    cellContent = find.widgetWithText(Align, '0').first;
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _defaultColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _defaultHorizontalMargin,
+    );
+
+    // CUSTOM VALUES
+    await tester.pumpWidget(MaterialApp(
+      home: Material(
+        child: PaginatedDataTable(
+          header: const Text('Test table'),
+          source: source,
+          rowsPerPage: 2,
+          availableRowsPerPage: const <int>[
+            2, 4, 8, 16,
+          ],
+          onRowsPerPageChanged: (int rowsPerPage) {},
+          onPageChanged: (int rowIndex) {},
+          columns: const <DataColumn>[
+            DataColumn(label: Text('Name')),
+            DataColumn(label: Text('Calories'), numeric: true),
+            DataColumn(label: Text('Generation')),
+          ],
+          horizontalMargin: _customHorizontalMargin,
+          columnSpacing: _customColumnSpacing,
+        ),
+      ),
+    ));
+
+    // custom first column padding
+    padding = find.widgetWithText(Padding, 'Frozen yogurt (0)').first;
+    cellContent = find.widgetWithText(Align, 'Frozen yogurt (0)');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customHorizontalMargin,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customColumnSpacing / 2,
+    );
+
+    // custom middle column padding
+    padding = find.widgetWithText(Padding, '159').first;
+    cellContent = find.widgetWithText(Align, '159');
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customColumnSpacing / 2,
+    );
+
+    // custom last column padding
+    padding = find.widgetWithText(Padding, '0').first;
+    cellContent = find.widgetWithText(Align, '0').first;
+    expect(
+      tester.getRect(cellContent).left - tester.getRect(padding).left,
+      _customColumnSpacing / 2,
+    );
+    expect(
+      tester.getRect(padding).right - tester.getRect(cellContent).right,
+      _customHorizontalMargin,
+    );
+  });
 }