packages/flutter/test/cupertino/scrollbar_paint_test.dart

// Copyright 2014 The Flutter 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/cupertino.dart';
import 'package:flutter_test/flutter_test.dart';

import '../rendering/mock_canvas.dart';

const Color _kScrollbarColor = Color(0x59000000);

// The `y` offset has to be larger than `ScrollDragController._bigThresholdBreakDistance`
// to prevent [motionStartDistanceThreshold] from affecting the actual drag distance.
const Offset _kGestureOffset = Offset(0, -25);
const Radius _kScrollbarRadius = Radius.circular(1.5);

void main() {
  testWidgets('Paints iOS spec', (WidgetTester tester) async {
    await tester.pumpWidget(
      const Directionality(
        textDirection: TextDirection.ltr,
        child: MediaQuery(
          data: MediaQueryData(),
          child: CupertinoScrollbar(
            child: SingleChildScrollView(
              child: SizedBox(width: 4000.0, height: 4000.0),
            ),
          ),
        ),
      ),
    );

    expect(find.byType(CupertinoScrollbar), isNot(paints..rrect()));

    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.byType(SingleChildScrollView)));
    await gesture.moveBy(_kGestureOffset);
    // Move back to original position.
    await gesture.moveBy(Offset.zero.translate(-_kGestureOffset.dx, -_kGestureOffset.dy));
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 500));
    expect(find.byType(CupertinoScrollbar), paints..rrect(
      color: _kScrollbarColor,
      rrect: RRect.fromRectAndRadius(
        const Rect.fromLTWH(
          800.0 - 3 - 3, // Screen width - margin - thickness.
          3.0, // Initial position is the top margin.
          3, // Thickness.
          // Fraction in viewport * scrollbar height - top, bottom margin.
          600.0 / 4000.0 * (600.0 - 2 * 3),
        ),
        _kScrollbarRadius,
      ),
    ));
  });

  testWidgets('Paints iOS spec with nav bar', (WidgetTester tester) async {
    await tester.pumpWidget(
      CupertinoApp(
        home: MediaQuery(
          data: const MediaQueryData(
            padding: EdgeInsets.fromLTRB(0, 20, 0, 34),
          ),
          child: CupertinoPageScaffold(
            navigationBar: const CupertinoNavigationBar(
              middle: Text('Title'),
              backgroundColor: Color(0x11111111),
            ),
            child: CupertinoScrollbar(
              child: ListView(
                children: const <Widget>[SizedBox(width: 4000, height: 4000)],
              ),
            ),
          ),
        ),
      ),
    );

    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.byType(ListView)));
    await gesture.moveBy(_kGestureOffset);
    // Move back to original position.
    await gesture.moveBy(Offset(-_kGestureOffset.dx, -_kGestureOffset.dy));
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 500));

    expect(find.byType(CupertinoScrollbar), paints..rrect(
      color: _kScrollbarColor,
      rrect: RRect.fromRectAndRadius(
        const Rect.fromLTWH(
          800.0 - 3 - 3, // Screen width - margin - thickness.
          44 + 20 + 3.0, // nav bar height + top margin
          3, // Thickness.
          // Fraction visible * (viewport size - padding - margin)
          // where Fraction visible = (viewport size - padding) / content size
          (600.0 - 34 - 44 - 20) / 4000.0 * (600.0 - 2 * 3 - 34 - 44 - 20),
        ),
        _kScrollbarRadius,
      ),
    ));
  });

  testWidgets("should not paint when there isn't enough space", (WidgetTester tester) async {
    await tester.pumpWidget(
      CupertinoApp(
        home: MediaQuery(
          data: const MediaQueryData(
            padding: EdgeInsets.fromLTRB(0, 20, 0, 34),
          ),
          child: CupertinoPageScaffold(
            navigationBar: const CupertinoNavigationBar(
              middle: Text('Title'),
              backgroundColor: Color(0x11111111),
            ),
            child: CupertinoScrollbar(
              child: ListView(
                physics: const AlwaysScrollableScrollPhysics(parent: BouncingScrollPhysics()),
                children: const <Widget> [SizedBox(width: 10, height: 10)],
              ),
            ),
          ),
        ),
      ),
    );
    final TestGesture gesture = await tester.startGesture(tester.getCenter(find.byType(ListView)));
    await gesture.moveBy(_kGestureOffset);
    // Move back to original position.
    await gesture.moveBy(Offset(-_kGestureOffset.dx, -_kGestureOffset.dy));
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 500));

    expect(find.byType(CupertinoScrollbar), isNot(paints..rrect()));

    // The scrollbar should not appear even when overscrolled.
    final TestGesture overscrollGesture = await tester.startGesture(tester.getCenter(find.byType(ListView)));
    await overscrollGesture.moveBy(_kGestureOffset);

    await tester.pump();
    await tester.pump(const Duration(milliseconds: 500));
    expect(find.byType(CupertinoScrollbar), isNot(paints..rrect()));
  });
}