flutter_flutter/packages/flutter/test/rendering/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 '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 EnginePhase, fail;

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

class TestRenderingFlutterBinding extends BindingBase with ServicesBinding, GestureBinding, SchedulerBinding, PaintingBinding, SemanticsBinding, RendererBinding {
  /// 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].
  TestRenderingFlutterBinding({ this.onErrors });

  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.');
        }
      }
    }
  }
}

TestRenderingFlutterBinding _renderer;
TestRenderingFlutterBinding get renderer {
  _renderer ??= TestRenderingFlutterBinding();
  return _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({ 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;
}