packages/flutter/test/widgets/slivers_test.dart

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter/rendering.dart';

Future<Null> test(WidgetTester tester, double offset, { double anchor: 0.0 }) {
  return tester.pumpWidget(
    new Directionality(
      textDirection: TextDirection.ltr,
      child: new Viewport(
        anchor: anchor / 600.0,
        offset: new ViewportOffset.fixed(offset),
        slivers: const <Widget>[
          const SliverToBoxAdapter(child: const SizedBox(height: 400.0)),
          const SliverToBoxAdapter(child: const SizedBox(height: 400.0)),
          const SliverToBoxAdapter(child: const SizedBox(height: 400.0)),
          const SliverToBoxAdapter(child: const SizedBox(height: 400.0)),
          const SliverToBoxAdapter(child: const SizedBox(height: 400.0)),
        ],
      ),
    ),
  );
}

void verify(WidgetTester tester, List<Offset> idealPositions, List<bool> idealVisibles) {
  final List<Offset> actualPositions = tester.renderObjectList<RenderBox>(find.byType(SizedBox, skipOffstage: false)).map<Offset>(
    (RenderBox target) => target.localToGlobal(const Offset(0.0, 0.0))
  ).toList();
  final List<bool> actualVisibles = tester.renderObjectList<RenderSliverToBoxAdapter>(find.byType(SliverToBoxAdapter, skipOffstage: false)).map<bool>(
    (RenderSliverToBoxAdapter target) => target.geometry.visible
  ).toList();
  expect(actualPositions, equals(idealPositions));
  expect(actualVisibles, equals(idealVisibles));
}

void main() {
  testWidgets('Viewport basic test', (WidgetTester tester) async {
    await test(tester, 0.0);
    expect(tester.renderObject<RenderBox>(find.byType(Viewport)).size, equals(const Size(800.0, 600.0)));
    verify(tester, <Offset>[
      const Offset(0.0, 0.0),
      const Offset(0.0, 400.0),
      const Offset(0.0, 800.0),
      const Offset(0.0, 1200.0),
      const Offset(0.0, 1600.0),
    ], <bool>[true, true, false, false, false]);

    await test(tester, 200.0);
    verify(tester, <Offset>[
      const Offset(0.0, -200.0),
      const Offset(0.0, 200.0),
      const Offset(0.0, 600.0),
      const Offset(0.0, 1000.0),
      const Offset(0.0, 1400.0),
    ], <bool>[true, true, false, false, false]);

    await test(tester, 600.0);
    verify(tester, <Offset>[
      const Offset(0.0, -600.0),
      const Offset(0.0, -200.0),
      const Offset(0.0, 200.0),
      const Offset(0.0, 600.0),
      const Offset(0.0, 1000.0),
    ], <bool>[false, true, true, false, false]);

    await test(tester, 900.0);
    verify(tester, <Offset>[
      const Offset(0.0, -900.0),
      const Offset(0.0, -500.0),
      const Offset(0.0, -100.0),
      const Offset(0.0, 300.0),
      const Offset(0.0, 700.0),
    ], <bool>[false, false, true, true, false]);
  });

  testWidgets('Viewport anchor test', (WidgetTester tester) async {
    await test(tester, 0.0, anchor: 100.0);
    expect(tester.renderObject<RenderBox>(find.byType(Viewport)).size, equals(const Size(800.0, 600.0)));
    verify(tester, <Offset>[
      const Offset(0.0, 100.0),
      const Offset(0.0, 500.0),
      const Offset(0.0, 900.0),
      const Offset(0.0, 1300.0),
      const Offset(0.0, 1700.0),
    ], <bool>[true, true, false, false, false]);

    await test(tester, 200.0, anchor: 100.0);
    verify(tester, <Offset>[
      const Offset(0.0, -100.0),
      const Offset(0.0, 300.0),
      const Offset(0.0, 700.0),
      const Offset(0.0, 1100.0),
      const Offset(0.0, 1500.0),
    ], <bool>[true, true, false, false, false]);

    await test(tester, 600.0, anchor: 100.0);
    verify(tester, <Offset>[
      const Offset(0.0, -500.0),
      const Offset(0.0, -100.0),
      const Offset(0.0, 300.0),
      const Offset(0.0, 700.0),
      const Offset(0.0, 1100.0),
    ], <bool>[false, true, true, false, false]);

    await test(tester, 900.0, anchor: 100.0);
    verify(tester, <Offset>[
      const Offset(0.0, -800.0),
      const Offset(0.0, -400.0),
      const Offset(0.0, 0.0),
      const Offset(0.0, 400.0),
      const Offset(0.0, 800.0),
    ], <bool>[false, false, true, true, false]);
  });

  testWidgets('Multiple grids and lists', (WidgetTester tester) async {
    await tester.pumpWidget(
      new Center(
        child: new SizedBox(
          width: 44.4,
          height: 60.0,
          child: new Directionality(
            textDirection: TextDirection.ltr,
            child: new CustomScrollView(
              slivers: <Widget>[
                new SliverList(
                  delegate: new SliverChildListDelegate(
                    <Widget>[
                      new Container(height: 22.2, child: const Text('TOP')),
                      new Container(height: 22.2),
                      new Container(height: 22.2),
                    ],
                  ),
                ),
                new SliverFixedExtentList(
                  itemExtent: 22.2,
                  delegate: new SliverChildListDelegate(
                    <Widget>[
                      new Container(),
                      new Container(child: const Text('A')),
                      new Container(),
                    ],
                  ),
                ),
                new SliverGrid(
                  gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
                    crossAxisCount: 2,
                  ),
                  delegate: new SliverChildListDelegate(
                    <Widget>[
                      new Container(),
                      new Container(child: const Text('B')),
                      new Container(),
                    ],
                  ),
                ),
                new SliverList(
                  delegate: new SliverChildListDelegate(
                    <Widget>[
                      new Container(height: 22.2),
                      new Container(height: 22.2),
                      new Container(height: 22.2, child: const Text('BOTTOM')),
                    ],
                  ),
                ),
              ],
            ),
          ),
        ),
      ),
    );
    final TestGesture gesture = await tester.startGesture(const Offset(400.0, 300.0));
    expect(find.text('TOP'), findsOneWidget);
    expect(find.text('A'), findsNothing);
    expect(find.text('B'), findsNothing);
    expect(find.text('BOTTOM'), findsNothing);
    await gesture.moveBy(const Offset(0.0, -70.0));
    await tester.pump();
    expect(find.text('TOP'), findsNothing);
    expect(find.text('A'), findsOneWidget);
    expect(find.text('B'), findsNothing);
    expect(find.text('BOTTOM'), findsNothing);
    await gesture.moveBy(const Offset(0.0, -70.0));
    await tester.pump();
    expect(find.text('TOP'), findsNothing);
    expect(find.text('A'), findsNothing);
    expect(find.text('B'), findsOneWidget);
    expect(find.text('BOTTOM'), findsNothing);
    await gesture.moveBy(const Offset(0.0, -70.0));
    await tester.pump();
    expect(find.text('TOP'), findsNothing);
    expect(find.text('A'), findsNothing);
    expect(find.text('B'), findsNothing);
    expect(find.text('BOTTOM'), findsOneWidget);
  });
}