packages/flutter/test/material/selection_area_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/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter_test/flutter_test.dart';

Offset textOffsetToPosition(RenderParagraph paragraph, int offset) {
  const Rect caret = Rect.fromLTWH(0.0, 0.0, 2.0, 20.0);
  final Offset localOffset = paragraph.getOffsetForCaret(TextPosition(offset: offset), caret);
  return paragraph.localToGlobal(localOffset);
}

void main() {
  testWidgets('SelectionArea uses correct selection controls', (WidgetTester tester) async {
    await tester.pumpWidget(const MaterialApp(
      home: SelectionArea(
        child: Text('abc'),
      ),
    ));
    final SelectableRegion region = tester.widget<SelectableRegion>(find.byType(SelectableRegion));

    switch (defaultTargetPlatform) {
      case TargetPlatform.android:
      case TargetPlatform.fuchsia:
        expect(region.selectionControls, materialTextSelectionControls);
        break;
      case TargetPlatform.iOS:
        expect(region.selectionControls, cupertinoTextSelectionControls);
        break;
      case TargetPlatform.linux:
      case TargetPlatform.windows:
        expect(region.selectionControls, desktopTextSelectionControls);
        break;
      case TargetPlatform.macOS:
        expect(region.selectionControls, cupertinoDesktopTextSelectionControls);
        break;
    }
  }, variant: TargetPlatformVariant.all());

  testWidgets('onSelectionChange is called when the selection changes', (WidgetTester tester) async {
    SelectedContent? content;

    await tester.pumpWidget(MaterialApp(
      home: SelectionArea(
        child: const Text('How are you'),
        onSelectionChanged: (SelectedContent? selectedContent) => content = selectedContent,
      ),
    ));
    final RenderParagraph paragraph = tester.renderObject<RenderParagraph>(find.descendant(of: find.text('How are you'), matching: find.byType(RichText)));
    final TestGesture gesture = await tester.startGesture(textOffsetToPosition(paragraph, 4), kind: PointerDeviceKind.mouse);
    expect(content, isNull);
    addTearDown(gesture.removePointer);
    await tester.pump();

    await gesture.moveTo(textOffsetToPosition(paragraph, 7));
    await gesture.up();
    await tester.pump();
    expect(content, isNotNull);
    expect(content!.plainText, 'are');

    // Backwards selection.
    await gesture.down(textOffsetToPosition(paragraph, 3));
    expect(content, isNull);
    await gesture.moveTo(textOffsetToPosition(paragraph, 0));
    await gesture.up();
    await tester.pump();
    expect(content, isNotNull);
    expect(content!.plainText, 'How');
  });
}