sky/packages/sky/lib/rendering/toggleable.dart

// Copyright 2015 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:sky' as sky;

import 'package:sky/animation/animated_value.dart';
import 'package:sky/animation/animation_performance.dart';
import 'package:sky/animation/curves.dart';
import 'package:sky/rendering/box.dart';
import 'package:sky/rendering/object.dart';
import 'package:sky/rendering/proxy_box.dart';

typedef void ValueChanged(bool value);

const Duration _kToggleDuration = const Duration(milliseconds: 200);

// RenderToggleable is a base class for material style toggleable controls with
// toggle animations. It handles storing the current value, dispatching
// ValueChanged on a tap gesture and driving a changed animation. Subclasses are
// responsible for painting.
abstract class RenderToggleable extends RenderConstrainedBox {
  RenderToggleable({bool value, Size size, ValueChanged onChanged})
      : _value = value,
        _onChanged = onChanged,
        super(additionalConstraints: new BoxConstraints.tight(size)) {
    _performance = new AnimationPerformance()
      ..variable = _position
      ..duration = _kToggleDuration
      ..progress = _value ? 1.0 : 0.0
      ..addListener(markNeedsPaint);
  }

  EventDisposition handleEvent(sky.Event event, BoxHitTestEntry entry) {
    if (event is sky.GestureEvent && event.type == 'gesturetap') {
      _onChanged(!_value);
      return EventDisposition.consumed;
    }
    return EventDisposition.ignored;
  }

  bool _value;
  bool get value => _value;

  void set value(bool value) {
    if (value == _value) return;
    _value = value;
    performance.play(value ? Direction.forward : Direction.reverse);
  }

  ValueChanged _onChanged;
  ValueChanged get onChanged => _onChanged;

  void set onChanged(ValueChanged onChanged) {
    _onChanged = onChanged;
  }

  final AnimatedValue<double> _position =
      new AnimatedValue<double>(0.0, end: 1.0, curve: easeIn, reverseCurve: easeOut);
  AnimatedValue<double> get position => _position;

  AnimationPerformance _performance;
  AnimationPerformance get performance => _performance;
}