Reduce motion: the source

since 0.7.0 or earlier Widgets and the rest
Open the live demo · Read the guide · View on GitHub
Regions the guide quotes: value (line 18), read (line 60), compare (line 84).
1/// What the player has already told the operating system, read as a default
2/// for a camera's own involuntary movement.
3///
4/// **`flutter3d_game`'s real `Accommodations` is not a dependency of this
5/// app.** It is nine lines wrapping `MediaQuery.maybeDisableAnimationsOf`;
6/// this page reimplements exactly that shape and calls the same real
7/// Flutter API, so the numbers below answer to this device's actual
8/// reduce-motion setting, not a stand-in for it.
9///
10/// Quoted by `accommodations.md` and shown whole in the Source tab.
11library;

13import 'package:flutter/widgets.dart';
14import 'package:flutter3d/flutter3d.dart';
15import 'package:flutter3d_showcase/src/demo/demo.dart';
16import 'package:vector_math/vector_math.dart';

18/// A default, never an override: a game reads this where the player has not
19/// said otherwise, and a slider they moved themselves still wins.
20final class _Accommodations {
const _Accommodations({this.reduceMotion = false});

factory _Accommodations.of(BuildContext context) => _Accommodations(
  reduceMotion: MediaQuery.maybeDisableAnimationsOf(context) ?? false,
);

final bool reduceMotion;

/// Nought when the player has asked for less movement: a camera that
/// shakes on every landing is exactly what the system setting is about.
double get cameraMotion => reduceMotion ? 0.0 : 1.0;

/// The same fallback for a full-screen flash, kept separate because a
/// flash is a photosensitivity question and a moving camera is a
/// vestibular one.
double get screenFlash => reduceMotion ? 0.0 : 1.0;
37}

39final class AccommodationsDemo extends ShowcaseDemo {
@override
Scene build(DemoContext context) {
  final material = Material(
    name: 'ball',
    baseColor: Vector4(0.8, 0.6, 0.4, 1.0),
  );
  final node = MeshNode(
    DeviceMesh.upload(context.device, SphereShape(segments: 16).build()),
    material,
  );
  return Scene()
    ..add(node)
    ..add(
      LightNode(name: 'sun', intensity: 3.0)
        ..setLocalForward(Vector3(-0.4, -1.0, -0.3)),
    );
}

@override
Widget? customBody(BuildContext buildContext, DemoContext context) {
  final accommodations = _Accommodations.of(buildContext);
  return Container(
    color: const Color(0xFF14161A),
    padding: const EdgeInsets.all(24),
    alignment: Alignment.topLeft,
    child: DefaultTextStyle(
      style: const TextStyle(color: Color(0xFFE8E8EC), fontSize: 16),
      child: Text(
        'this device asks for reduced motion: '
        '${accommodations.reduceMotion}\n'
        'a camera rig would default its own motion to '
        '${accommodations.cameraMotion}\n'
        'a full-screen flash would default to '
        '${accommodations.screenFlash}',
      ),
    ),
  );
}

@override
void verify(Scene scene, FrameResult frame) {
  if (frame.drawCalls < 1) {
    throw StateError('the ball was not drawn');
  }
  const off = _Accommodations();
  const on = _Accommodations(reduceMotion: true);
  if (off.cameraMotion != 1.0 || on.cameraMotion != 0.0) {
    throw StateError(
      'reduced motion should zero the camera motion '
      'default and nothing else should',
    );
  }
}
93}