blob: f383dfad86856fe04f4ce1827059732fe966f8b3 [file] [log] [blame]
// Copyright 2018 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 'dart:ui';
import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';
void main() {
testWidgets('Viewport getOffsetToReveal - down', (WidgetTester tester) async {
List<Widget> children;
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 200.0,
width: 300.0,
child: ListView(
controller: ScrollController(initialScrollOffset: 300.0),
children: children = List<Widget>.generate(20, (int i) {
return Container(
height: 100.0,
width: 300.0,
child: Text('Tile $i'),
);
}),
),
),
),
),
);
final RenderAbstractViewport viewport = tester.allRenderObjects.firstWhere((RenderObject r) => r is RenderAbstractViewport);
final RenderObject target = tester.renderObject(find.byWidget(children[5], skipOffstage: false));
RevealedOffset revealed = viewport.getOffsetToReveal(target, 0.0);
expect(revealed.offset, 500.0);
expect(revealed.rect, Rect.fromLTWH(0.0, 0.0, 300.0, 100.0));
revealed = viewport.getOffsetToReveal(target, 1.0);
expect(revealed.offset, 400.0);
expect(revealed.rect, Rect.fromLTWH(0.0, 100.0, 300.0, 100.0));
revealed = viewport.getOffsetToReveal(target, 0.0, rect: Rect.fromLTWH(40.0, 40.0, 10.0, 10.0));
expect(revealed.offset, 540.0);
expect(revealed.rect, Rect.fromLTWH(40.0, 0.0, 10.0, 10.0));
revealed = viewport.getOffsetToReveal(target, 1.0, rect: Rect.fromLTWH(40.0, 40.0, 10.0, 10.0));
expect(revealed.offset, 350.0);
expect(revealed.rect, Rect.fromLTWH(40.0, 190.0, 10.0, 10.0));
});
testWidgets('Viewport getOffsetToReveal - right', (WidgetTester tester) async {
List<Widget> children;
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 300.0,
width: 200.0,
child: ListView(
scrollDirection: Axis.horizontal,
controller: ScrollController(initialScrollOffset: 300.0),
children: children = List<Widget>.generate(20, (int i) {
return Container(
height: 300.0,
width: 100.0,
child: Text('Tile $i'),
);
}),
),
),
),
),
);
final RenderAbstractViewport viewport = tester.allRenderObjects.firstWhere((RenderObject r) => r is RenderAbstractViewport);
final RenderObject target = tester.renderObject(find.byWidget(children[5], skipOffstage: false));
RevealedOffset revealed = viewport.getOffsetToReveal(target, 0.0);
expect(revealed.offset, 500.0);
expect(revealed.rect, Rect.fromLTWH(0.0, 0.0, 100.0, 300.0));
revealed = viewport.getOffsetToReveal(target, 1.0);
expect(revealed.offset, 400.0);
expect(revealed.rect, Rect.fromLTWH(100.0, 0.0, 100.0, 300.0));
revealed = viewport.getOffsetToReveal(target, 0.0, rect: Rect.fromLTWH(40.0, 40.0, 10.0, 10.0));
expect(revealed.offset, 540.0);
expect(revealed.rect, Rect.fromLTWH(0.0, 40.0, 10.0, 10.0));
revealed = viewport.getOffsetToReveal(target, 1.0, rect: Rect.fromLTWH(40.0, 40.0, 10.0, 10.0));
expect(revealed.offset, 350.0);
expect(revealed.rect, Rect.fromLTWH(190.0, 40.0, 10.0, 10.0));
});
testWidgets('Viewport getOffsetToReveal - up', (WidgetTester tester) async {
List<Widget> children;
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 200.0,
width: 300.0,
child: ListView(
controller: ScrollController(initialScrollOffset: 300.0),
reverse: true,
children: children = List<Widget>.generate(20, (int i) {
return Container(
height: 100.0,
width: 300.0,
child: Text('Tile $i'),
);
}),
),
),
),
),
);
final RenderAbstractViewport viewport = tester.allRenderObjects.firstWhere((RenderObject r) => r is RenderAbstractViewport);
final RenderObject target = tester.renderObject(find.byWidget(children[5], skipOffstage: false));
RevealedOffset revealed = viewport.getOffsetToReveal(target, 0.0);
expect(revealed.offset, 500.0);
expect(revealed.rect, Rect.fromLTWH(0.0, 100.0, 300.0, 100.0));
revealed = viewport.getOffsetToReveal(target, 1.0);
expect(revealed.offset, 400.0);
expect(revealed.rect, Rect.fromLTWH(0.0, 0.0, 300.0, 100.0));
revealed = viewport.getOffsetToReveal(target, 0.0, rect: Rect.fromLTWH(40.0, 40.0, 10.0, 10.0));
expect(revealed.offset, 550.0);
expect(revealed.rect, Rect.fromLTWH(40.0, 190.0, 10.0, 10.0));
revealed = viewport.getOffsetToReveal(target, 1.0, rect: Rect.fromLTWH(40.0, 40.0, 10.0, 10.0));
expect(revealed.offset, 360.0);
expect(revealed.rect, Rect.fromLTWH(40.0, 0.0, 10.0, 10.0));
});
testWidgets('Viewport getOffsetToReveal - left', (WidgetTester tester) async {
List<Widget> children;
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 300.0,
width: 200.0,
child: ListView(
scrollDirection: Axis.horizontal,
reverse: true,
controller: ScrollController(initialScrollOffset: 300.0),
children: children = List<Widget>.generate(20, (int i) {
return Container(
height: 300.0,
width: 100.0,
child: Text('Tile $i'),
);
}),
),
),
),
),
);
final RenderAbstractViewport viewport = tester.allRenderObjects.firstWhere((RenderObject r) => r is RenderAbstractViewport);
final RenderObject target = tester.renderObject(find.byWidget(children[5], skipOffstage: false));
RevealedOffset revealed = viewport.getOffsetToReveal(target, 0.0);
expect(revealed.offset, 500.0);
expect(revealed.rect, Rect.fromLTWH(100.0, 0.0, 100.0, 300.0));
revealed = viewport.getOffsetToReveal(target, 1.0);
expect(revealed.offset, 400.0);
expect(revealed.rect, Rect.fromLTWH(0.0, 0.0, 100.0, 300.0));
revealed = viewport.getOffsetToReveal(target, 0.0, rect: Rect.fromLTWH(40.0, 40.0, 10.0, 10.0));
expect(revealed.offset, 550.0);
expect(revealed.rect, Rect.fromLTWH(190.0, 40.0, 10.0, 10.0));
revealed = viewport.getOffsetToReveal(target, 1.0, rect: Rect.fromLTWH(40.0, 40.0, 10.0, 10.0));
expect(revealed.offset, 360.0);
expect(revealed.rect, Rect.fromLTWH(0.0, 40.0, 10.0, 10.0));
});
testWidgets('Viewport getOffsetToReveal Sliver - down', (WidgetTester tester) async {
final List<Widget> children = <Widget>[];
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 200.0,
width: 300.0,
child: CustomScrollView(
controller: ScrollController(initialScrollOffset: 300.0),
slivers: List<Widget>.generate(20, (int i) {
final Widget sliver = SliverToBoxAdapter(
child: Container(
height: 100.0,
child: Text('Tile $i'),
),
);
children.add(sliver);
return SliverPadding(
padding: const EdgeInsets.all(22.0),
sliver: sliver,
);
}),
),
),
),
),
);
final RenderAbstractViewport viewport = tester.allRenderObjects.firstWhere((RenderObject r) => r is RenderAbstractViewport);
final RenderObject target = tester.renderObject(find.byWidget(children[5], skipOffstage: false));
RevealedOffset revealed = viewport.getOffsetToReveal(target, 0.0);
expect(revealed.offset, 5 * (100 + 22 + 22) + 22);
revealed = viewport.getOffsetToReveal(target, 1.0);
expect(revealed.offset, 5 * (100 + 22 + 22) + 22 - 100);
});
testWidgets('Viewport getOffsetToReveal Sliver - right', (WidgetTester tester) async {
final List<Widget> children = <Widget>[];
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 300.0,
width: 200.0,
child: CustomScrollView(
scrollDirection: Axis.horizontal,
controller: ScrollController(initialScrollOffset: 300.0),
slivers: List<Widget>.generate(20, (int i) {
final Widget sliver = SliverToBoxAdapter(
child: Container(
width: 100.0,
child: Text('Tile $i'),
),
);
children.add(sliver);
return SliverPadding(
padding: const EdgeInsets.all(22.0),
sliver: sliver,
);
}),
),
),
),
),
);
final RenderAbstractViewport viewport = tester.allRenderObjects.firstWhere((RenderObject r) => r is RenderAbstractViewport);
final RenderObject target = tester.renderObject(find.byWidget(children[5], skipOffstage: false));
RevealedOffset revealed = viewport.getOffsetToReveal(target, 0.0);
expect(revealed.offset, 5 * (100 + 22 + 22) + 22);
revealed = viewport.getOffsetToReveal(target, 1.0);
expect(revealed.offset, 5 * (100 + 22 + 22) + 22 - 100);
});
testWidgets('Viewport getOffsetToReveal Sliver - up', (WidgetTester tester) async {
final List<Widget> children = <Widget>[];
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 200.0,
width: 300.0,
child: CustomScrollView(
controller: ScrollController(initialScrollOffset: 300.0),
reverse: true,
slivers: List<Widget>.generate(20, (int i) {
final Widget sliver = SliverToBoxAdapter(
child: Container(
height: 100.0,
child: Text('Tile $i'),
),
);
children.add(sliver);
return SliverPadding(
padding: const EdgeInsets.all(22.0),
sliver: sliver,
);
}),
),
),
),
),
);
final RenderAbstractViewport viewport = tester.allRenderObjects.firstWhere((RenderObject r) => r is RenderAbstractViewport);
final RenderObject target = tester.renderObject(find.byWidget(children[5], skipOffstage: false));
RevealedOffset revealed = viewport.getOffsetToReveal(target, 0.0);
expect(revealed.offset, 5 * (100 + 22 + 22) + 22);
revealed = viewport.getOffsetToReveal(target, 1.0);
expect(revealed.offset, 5 * (100 + 22 + 22) + 22 - 100);
});
testWidgets('Viewport getOffsetToReveal Sliver - left', (WidgetTester tester) async {
final List<Widget> children = <Widget>[];
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 300.0,
width: 200.0,
child: CustomScrollView(
scrollDirection: Axis.horizontal,
reverse: true,
controller: ScrollController(initialScrollOffset: 300.0),
slivers: List<Widget>.generate(20, (int i) {
final Widget sliver = SliverToBoxAdapter(
child: Container(
width: 100.0,
child: Text('Tile $i'),
),
);
children.add(sliver);
return SliverPadding(
padding: const EdgeInsets.all(22.0),
sliver: sliver,
);
}),
),
),
),
),
);
final RenderAbstractViewport viewport = tester.allRenderObjects.firstWhere((RenderObject r) => r is RenderAbstractViewport);
final RenderObject target = tester.renderObject(find.byWidget(children[5], skipOffstage: false));
RevealedOffset revealed = viewport.getOffsetToReveal(target, 0.0);
expect(revealed.offset, 5 * (100 + 22 + 22) + 22);
revealed = viewport.getOffsetToReveal(target, 1.0);
expect(revealed.offset, 5 * (100 + 22 + 22) + 22 - 100);
});
testWidgets('Nested Viewports showOnScreen', (WidgetTester tester) async {
final List<List<Widget>> children = List<List<Widget>>(10);
final List<ScrollController> controllersX = List<ScrollController>.generate(10, (int i) => ScrollController(initialScrollOffset: 400.0));
final ScrollController controllerY = ScrollController(initialScrollOffset: 400.0);
/// Builds a gird:
///
/// <- x ->
/// 0 1 2 3 4 5 6 7 8 9
/// 0 c c c c c c c c c c
/// 1 c c c c c c c c c c
/// 2 c c c c c c c c c c
/// 3 c c c c c c c c c c y
/// 4 c c c c v v c c c c
/// 5 c c c c v v c c c c
/// 6 c c c c c c c c c c
/// 7 c c c c c c c c c c
/// 8 c c c c c c c c c c
/// 9 c c c c c c c c c c
///
/// Each c is a 100x100 container, v are containers visible in initial
/// viewport.
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 200.0,
width: 200.0,
child: ListView(
controller: controllerY,
children: List<Widget>.generate(10, (int y) {
return Container(
height: 100.0,
child: ListView(
scrollDirection: Axis.horizontal,
controller: controllersX[y],
children: children[y] = List<Widget>.generate(10, (int x) {
return Container(
height: 100.0,
width: 100.0,
child: Text('$x,$y'),
);
}),
),
);
}),
),
),
),
),
);
// Already in viewport
tester.renderObject(find.byWidget(children[4][4], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controllersX[4].offset, 400.0);
expect(controllerY.offset, 400.0);
controllersX[4].jumpTo(400.0);
controllerY.jumpTo(400.0);
await tester.pumpAndSettle();
// Above viewport
tester.renderObject(find.byWidget(children[3][4], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controllersX[3].offset, 400.0);
expect(controllerY.offset, 300.0);
controllersX[3].jumpTo(400.0);
controllerY.jumpTo(400.0);
await tester.pumpAndSettle();
// Below viewport
tester.renderObject(find.byWidget(children[6][4], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controllersX[6].offset, 400.0);
expect(controllerY.offset, 500.0);
controllersX[6].jumpTo(400.0);
controllerY.jumpTo(400.0);
await tester.pumpAndSettle();
// Left of viewport
tester.renderObject(find.byWidget(children[4][3], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controllersX[4].offset, 300.0);
expect(controllerY.offset, 400.0);
controllersX[4].jumpTo(400.0);
controllerY.jumpTo(400.0);
await tester.pumpAndSettle();
// Right of viewport
tester.renderObject(find.byWidget(children[4][6], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controllersX[4].offset, 500.0);
expect(controllerY.offset, 400.0);
controllersX[4].jumpTo(400.0);
controllerY.jumpTo(400.0);
await tester.pumpAndSettle();
// Above and left of viewport
tester.renderObject(find.byWidget(children[3][3], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controllersX[3].offset, 300.0);
expect(controllerY.offset, 300.0);
controllersX[3].jumpTo(400.0);
controllerY.jumpTo(400.0);
await tester.pumpAndSettle();
// Below and left of viewport
tester.renderObject(find.byWidget(children[6][3], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controllersX[6].offset, 300.0);
expect(controllerY.offset, 500.0);
controllersX[6].jumpTo(400.0);
controllerY.jumpTo(400.0);
await tester.pumpAndSettle();
// Above and right of viewport
tester.renderObject(find.byWidget(children[3][6], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controllersX[3].offset, 500.0);
expect(controllerY.offset, 300.0);
controllersX[3].jumpTo(400.0);
controllerY.jumpTo(400.0);
await tester.pumpAndSettle();
// Below and right of viewport
tester.renderObject(find.byWidget(children[6][6], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controllersX[6].offset, 500.0);
expect(controllerY.offset, 500.0);
controllersX[6].jumpTo(400.0);
controllerY.jumpTo(400.0);
await tester.pumpAndSettle();
// Below and right of viewport with animations
tester.renderObject(find.byWidget(children[6][6], skipOffstage: false)).showOnScreen(duration: const Duration(seconds: 2));
await tester.pump();
await tester.pump(const Duration(seconds: 1));
expect(tester.hasRunningAnimations, isTrue);
expect(controllersX[6].offset, greaterThan(400.0));
expect(controllersX[6].offset, lessThan(500.0));
expect(controllerY.offset, greaterThan(400.0));
expect(controllerY.offset, lessThan(500.0));
await tester.pumpAndSettle();
expect(controllersX[6].offset, 500.0);
expect(controllerY.offset, 500.0);
});
group('Nested viewports (same orientation) showOnScreen', () {
List<Widget> children;
Future<void> buildNestedScroller({ WidgetTester tester, ScrollController inner, ScrollController outer }) {
return tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 200.0,
width: 300.0,
child: ListView(
controller: outer,
children: <Widget>[
Container(
height: 200.0,
),
Container(
height: 200.0,
width: 300.0,
child: ListView(
controller: inner,
children: children = List<Widget>.generate(10, (int i) {
return Container(
height: 100.0,
width: 300.0,
child: Text('$i'),
);
}),
),
),
Container(
height: 200.0,
),
],
),
),
),
),
);
}
testWidgets('in view in inner, but not in outer', (WidgetTester tester) async {
final ScrollController inner = ScrollController();
final ScrollController outer = ScrollController();
await buildNestedScroller(
tester: tester,
inner: inner,
outer: outer,
);
expect(outer.offset, 0.0);
expect(inner.offset, 0.0);
tester.renderObject(find.byWidget(children[0], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(inner.offset, 0.0);
expect(outer.offset, 100.0);
});
testWidgets('not in view of neither inner nor outer', (WidgetTester tester) async {
final ScrollController inner = ScrollController();
final ScrollController outer = ScrollController();
await buildNestedScroller(
tester: tester,
inner: inner,
outer: outer,
);
expect(outer.offset, 0.0);
expect(inner.offset, 0.0);
tester.renderObject(find.byWidget(children[4], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(inner.offset, 300.0);
expect(outer.offset, 200.0);
});
testWidgets('in view in inner and outer', (WidgetTester tester) async {
final ScrollController inner = ScrollController(initialScrollOffset: 200.0);
final ScrollController outer = ScrollController(initialScrollOffset: 200.0);
await buildNestedScroller(
tester: tester,
inner: inner,
outer: outer,
);
expect(outer.offset, 200.0);
expect(inner.offset, 200.0);
tester.renderObject(find.byWidget(children[2])).showOnScreen();
await tester.pumpAndSettle();
expect(outer.offset, 200.0);
expect(inner.offset, 200.0);
});
testWidgets('inner shown in outer, but item not visible', (WidgetTester tester) async {
final ScrollController inner = ScrollController(initialScrollOffset: 200.0);
final ScrollController outer = ScrollController(initialScrollOffset: 200.0);
await buildNestedScroller(
tester: tester,
inner: inner,
outer: outer,
);
expect(outer.offset, 200.0);
expect(inner.offset, 200.0);
tester.renderObject(find.byWidget(children[5], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(outer.offset, 200.0);
expect(inner.offset, 400.0);
});
testWidgets('inner half shown in outer, item only visible in inner', (WidgetTester tester) async {
final ScrollController inner = ScrollController();
final ScrollController outer = ScrollController(initialScrollOffset: 100.0);
await buildNestedScroller(
tester: tester,
inner: inner,
outer: outer,
);
expect(outer.offset, 100.0);
expect(inner.offset, 0.0);
tester.renderObject(find.byWidget(children[1])).showOnScreen();
await tester.pumpAndSettle();
expect(outer.offset, 200.0);
expect(inner.offset, 0.0);
});
});
testWidgets('Nested Viewports showOnScreen with allowImplicitScrolling=false for inner viewport', (WidgetTester tester) async {
// Regression test for https://github.com/flutter/flutter/issues/20893.
List<Widget> slivers;
final ScrollController controllerX = ScrollController(initialScrollOffset: 0.0);
final ScrollController controllerY = ScrollController(initialScrollOffset: 0.0);
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 200.0,
width: 200.0,
child: ListView(
controller: controllerY,
children: <Widget>[
Container(
height: 150.0,
),
Container(
height: 100.0,
child: ListView(
physics: const PageScrollPhysics(), // Turns off `allowImplicitScrolling`
scrollDirection: Axis.horizontal,
controller: controllerX,
children: slivers = <Widget>[
Container(
width: 150.0,
),
Container(
width: 150.0,
),
],
),
),
Container(
height: 150.0,
),
],
),
),
),
),
);
tester.renderObject(find.byWidget(slivers[1])).showOnScreen();
await tester.pumpAndSettle();
expect(controllerX.offset, 0.0);
expect(controllerY.offset, 50.0);
});
testWidgets('Nested Viewports showOnScreen on Sliver with allowImplicitScrolling=false for inner viewport', (WidgetTester tester) async {
Widget sliver;
final ScrollController controllerX = ScrollController(initialScrollOffset: 0.0);
final ScrollController controllerY = ScrollController(initialScrollOffset: 0.0);
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 200.0,
width: 200.0,
child: ListView(
controller: controllerY,
children: <Widget>[
Container(
height: 150.0,
),
Container(
height: 100.0,
child: CustomScrollView(
physics: const PageScrollPhysics(), // Turns off `allowImplicitScrolling`
scrollDirection: Axis.horizontal,
controller: controllerX,
slivers: <Widget>[
SliverPadding(
padding: const EdgeInsets.all(25.0),
sliver: SliverToBoxAdapter(
child: Container(
width: 100.0,
),
),
),
SliverPadding(
padding: const EdgeInsets.all(25.0),
sliver: sliver = SliverToBoxAdapter(
child: Container(
width: 100.0,
),
),
),
],
),
),
Container(
height: 150.0,
),
],
),
),
),
),
);
tester.renderObject(find.byWidget(sliver)).showOnScreen();
await tester.pumpAndSettle();
expect(controllerX.offset, 0.0);
expect(controllerY.offset, 25.0);
});
testWidgets('Viewport showOnScreen with objects larger than viewport', (WidgetTester tester) async {
List<Widget> children;
ScrollController controller;
await tester.pumpWidget(
Directionality(
textDirection: TextDirection.ltr,
child: Center(
child: Container(
height: 200.0,
child: ListView(
controller: controller = ScrollController(initialScrollOffset: 300.0),
children: children = List<Widget>.generate(20, (int i) {
return Container(
height: 300.0,
child: Text('Tile $i'),
);
}),
),
),
),
),
);
expect(controller.offset, 300.0);
// Already aligned with leading edge, nothing happens.
tester.renderObject(find.byWidget(children[1], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controller.offset, 300.0);
// Above leading edge aligns trailing edges
tester.renderObject(find.byWidget(children[0], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controller.offset, 100.0);
// Below trailing edge aligns leading edges
tester.renderObject(find.byWidget(children[1], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controller.offset, 300.0);
controller.jumpTo(250.0);
await tester.pumpAndSettle();
expect(controller.offset, 250.0);
// Partly visible across leading edge aligns trailing edges
tester.renderObject(find.byWidget(children[0], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controller.offset, 100.0);
controller.jumpTo(150.0);
await tester.pumpAndSettle();
expect(controller.offset, 150.0);
// Partly visible across trailing edge aligns leading edges
tester.renderObject(find.byWidget(children[1], skipOffstage: false)).showOnScreen();
await tester.pumpAndSettle();
expect(controller.offset, 300.0);
});
}