rendering_tester.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 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter/services.dart';
import 'package:flutter_test/flutter_test.dart' show TestDefaultBinaryMessengerBinding, EnginePhase, fail;

export 'package:flutter/foundation.dart' show FlutterError, FlutterErrorDetails;
export 'package:flutter_test/flutter_test.dart' show TestDefaultBinaryMessengerBinding, EnginePhase;

class TestRenderingFlutterBinding extends BindingBase with SchedulerBinding, ServicesBinding, GestureBinding, PaintingBinding, SemanticsBinding, RendererBinding, TestDefaultBinaryMessengerBinding {
  /// Creates a binding for testing rendering library functionality.
  ///
  /// If [onErrors] is not null, it is called if [FlutterError] caught any errors
  /// while drawing the frame. If [onErrors] is null and [FlutterError] caught at least
  /// one error, this function fails the test. A test may override [onErrors] and
  /// inspect errors using [takeFlutterErrorDetails].
  ///
  /// Errors caught between frames will cause the test to fail unless
  /// [FlutterError.onError] has been overridden.
  TestRenderingFlutterBinding({ this.onErrors }) {
    FlutterError.onError = (FlutterErrorDetails details) {
      FlutterError.dumpErrorToConsole(details);
      Zone.current.parent!.handleUncaughtError(details.exception, details.stack!);
    };
  }

  final List<FlutterErrorDetails> _errors = <FlutterErrorDetails>[];

  /// A function called after drawing a frame if [FlutterError] caught any errors.
  ///
  /// This function is expected to inspect these errors and decide whether they
  /// are expected or not. Use [takeFlutterErrorDetails] to take one error at a
  /// time, or [takeAllFlutterErrorDetails] to iterate over all errors.
  VoidCallback? onErrors;

  /// Returns the error least recently caught by [FlutterError] and removes it
  /// from the list of captured errors.
  ///
  /// Returns null if no errors were captures, or if the list was exhausted by
  /// calling this method repeatedly.
  FlutterErrorDetails? takeFlutterErrorDetails() {
    if (_errors.isEmpty) {
      return null;
    }
    return _errors.removeAt(0);
  }

  /// Returns all error details caught by [FlutterError] from least recently caught to
  /// most recently caught, and removes them from the list of captured errors.
  ///
  /// The returned iterable takes errors lazily. If, for example, you iterate over 2
  /// errors, but there are 5 errors total, this binding will still fail the test.
  /// Tests are expected to take and inspect all errors.
  Iterable<FlutterErrorDetails> takeAllFlutterErrorDetails() sync* {
    // sync* and yield are used for lazy evaluation. Otherwise, the list would be
    // drained eagerly and allow a test pass with unexpected errors.
    while (_errors.isNotEmpty) {
      yield _errors.removeAt(0);
    }
  }

  /// Returns all exceptions caught by [FlutterError] from least recently caught to
  /// most recently caught, and removes them from the list of captured errors.
  ///
  /// The returned iterable takes errors lazily. If, for example, you iterate over 2
  /// errors, but there are 5 errors total, this binding will still fail the test.
  /// Tests are expected to take and inspect all errors.
  Iterable<dynamic> takeAllFlutterExceptions() sync* {
    // sync* and yield are used for lazy evaluation. Otherwise, the list would be
    // drained eagerly and allow a test pass with unexpected errors.
    while (_errors.isNotEmpty) {
      yield _errors.removeAt(0).exception;
    }
  }

  EnginePhase phase = EnginePhase.composite;

  @override
  void drawFrame() {
    assert(phase != EnginePhase.build, 'rendering_tester does not support testing the build phase; use flutter_test instead');
    final FlutterExceptionHandler? oldErrorHandler = FlutterError.onError;
    FlutterError.onError = (FlutterErrorDetails details) {
      _errors.add(details);
    };
    try {
      pipelineOwner.flushLayout();
      if (phase == EnginePhase.layout)
        return;
      pipelineOwner.flushCompositingBits();
      if (phase == EnginePhase.compositingBits)
        return;
      pipelineOwner.flushPaint();
      if (phase == EnginePhase.paint)
        return;
      renderView.compositeFrame();
      if (phase == EnginePhase.composite)
        return;
      pipelineOwner.flushSemantics();
      if (phase == EnginePhase.flushSemantics)
        return;
      assert(phase == EnginePhase.flushSemantics || phase == EnginePhase.sendSemanticsUpdate);
    } finally {
      FlutterError.onError = oldErrorHandler;
      if (_errors.isNotEmpty) {
        if (onErrors != null) {
          onErrors!();
          if (_errors.isNotEmpty) {
            _errors.forEach(FlutterError.dumpErrorToConsole);
            fail('There are more errors than the test inspected using TestRenderingFlutterBinding.takeFlutterErrorDetails.');
          }
        } else {
          _errors.forEach(FlutterError.dumpErrorToConsole);
          fail('Caught error while rendering frame. See preceding logs for details.');
        }
      }
    }
  }
}

late final TestRenderingFlutterBinding _renderer = TestRenderingFlutterBinding();
TestRenderingFlutterBinding get renderer => _renderer;


/// Place the box in the render tree, at the given size and with the given
/// alignment on the screen.
///
/// If you've updated `box` and want to lay it out again, use [pumpFrame].
///
/// Once a particular [RenderBox] has been passed to [layout], it cannot easily
/// be put in a different place in the tree or passed to [layout] again, because
/// [layout] places the given object into another [RenderBox] which you would
/// need to unparent it from (but that box isn't itself made available).
///
/// The EnginePhase must not be [EnginePhase.build], since the rendering layer
/// has no build phase.
///
/// If `onErrors` is not null, it is set as [TestRenderingFlutterBinding.onError].
void layout(
  RenderBox box, {
  BoxConstraints? constraints,
  Alignment alignment = Alignment.center,
  EnginePhase phase = EnginePhase.layout,
  VoidCallback? onErrors,
}) {
  assert(box != null); // If you want to just repump the last box, call pumpFrame().
  assert(box.parent == null); // We stick the box in another, so you can't reuse it easily, sorry.

  renderer.renderView.child = null;
  if (constraints != null) {
    box = RenderPositionedBox(
      alignment: alignment,
      child: RenderConstrainedBox(
        additionalConstraints: constraints,
        child: box,
      ),
    );
  }
  renderer.renderView.child = box;

  pumpFrame(phase: phase, onErrors: onErrors);
}

/// Pumps a single frame.
///
/// If `onErrors` is not null, it is set as [TestRenderingFlutterBinding.onError].
void pumpFrame({ EnginePhase phase = EnginePhase.layout, VoidCallback? onErrors }) {
  assert(renderer != null);
  assert(renderer.renderView != null);
  assert(renderer.renderView.child != null); // call layout() first!

  if (onErrors != null) {
    renderer.onErrors = onErrors;
  }

  renderer.phase = phase;
  renderer.drawFrame();
}

class TestCallbackPainter extends CustomPainter {
  const TestCallbackPainter({ required this.onPaint });

  final VoidCallback onPaint;

  @override
  void paint(Canvas canvas, Size size) {
    onPaint();
  }

  @override
  bool shouldRepaint(TestCallbackPainter oldPainter) => true;
}

class RenderSizedBox extends RenderBox {
  RenderSizedBox(this._size);

  final Size _size;

  @override
  double computeMinIntrinsicWidth(double height) {
    return _size.width;
  }

  @override
  double computeMaxIntrinsicWidth(double height) {
    return _size.width;
  }

  @override
  double computeMinIntrinsicHeight(double width) {
    return _size.height;
  }

  @override
  double computeMaxIntrinsicHeight(double width) {
    return _size.height;
  }

  @override
  bool get sizedByParent => true;

  @override
  void performResize() {
    size = constraints.constrain(_size);
  }

  @override
  void performLayout() { }

  @override
  bool hitTestSelf(Offset position) => true;
}

class FakeTickerProvider implements TickerProvider {
  @override
  Ticker createTicker(TickerCallback onTick, [ bool disableAnimations = false ]) {
    return FakeTicker();
  }
}

class FakeTicker implements Ticker {
  @override
  bool muted = false;

  @override
  void absorbTicker(Ticker originalTicker) { }

  @override
  String? get debugLabel => null;

  @override
  bool get isActive => throw UnimplementedError();

  @override
  bool get isTicking => throw UnimplementedError();

  @override
  bool get scheduled => throw UnimplementedError();

  @override
  bool get shouldScheduleTick => throw UnimplementedError();

  @override
  void dispose() { }

  @override
  void scheduleTick({ bool rescheduling = false }) { }

  @override
  TickerFuture start() {
    throw UnimplementedError();
  }

  @override
  void stop({ bool canceled = false }) { }

  @override
  void unscheduleTick() { }

  @override
  String toString({ bool debugIncludeStack = false }) => super.toString();

  @override
  DiagnosticsNode describeForError(String name) {
    return DiagnosticsProperty<Ticker>(name, this, style: DiagnosticsTreeStyle.errorProperty);
  }
}

class TestClipPaintingContext extends PaintingContext {
  TestClipPaintingContext() : super(ContainerLayer(), Rect.zero);

  @override
  ClipRectLayer? pushClipRect(
    bool needsCompositing,
    Offset offset,
    Rect clipRect,
    PaintingContextCallback painter, {
    Clip clipBehavior = Clip.hardEdge,
    ClipRectLayer? oldLayer,
  }) {
    this.clipBehavior = clipBehavior;
  }

  Clip clipBehavior = Clip.none;
}

void expectOverflowedErrors() {
  final FlutterErrorDetails errorDetails = renderer.takeFlutterErrorDetails()!;
  final bool overflowed = errorDetails.toString().contains('overflowed');
  if (!overflowed) {
    FlutterError.reportError(errorDetails);
  }
}

RenderConstrainedBox get box200x200 =>
    RenderConstrainedBox(additionalConstraints: const BoxConstraints.tightFor(height: 200.0, width: 200.0));