64 lines
1.9 KiB
Dart
64 lines
1.9 KiB
Dart
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// Auto dark/bright from the tablet's light sensor. The Redmi Pad SE has no separate one:
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// Xiaomi derives it from the front camera ("camera_light_Sensor") and offers it as
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// Android's ordinary light sensor, the one auto-brightness reads. No camera permission.
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import 'package:flutter/services.dart';
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/// Light levels in lux, about once a second, from MainActivity. Ends at once (an error,
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/// which [Themes.followLight] ignores) where there is no sensor or no Android side.
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Stream<double> lightLevels() =>
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const EventChannel('yukart/light')
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.receiveBroadcastStream()
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.map((e) => (e as num).toDouble());
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/// Dark or bright from light levels, with a gap and a hold so dusk, shade and
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/// passing lights do not flicker it.
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class LightSwitch {
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/// Dark at or below this.
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static const darkAt = 15.0;
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/// Bright at or above this; in between, whatever it was.
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static const brightAt = 60.0;
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/// How long a level must last before it switches.
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static const hold = Duration(seconds: 5);
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bool? _dark;
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DateTime? _since;
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bool? get isDark => _dark;
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/// A change is waiting out its hold.
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bool get pending => _since != null;
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/// The hold has passed with no reading against it (a sensor that reports only on
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/// change goes quiet): make the waiting change.
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void settle() {
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if (_since == null) return;
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_dark = !_dark!;
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_since = null;
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}
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/// Feed one reading; returns the verdict (null until a reading outside the gap).
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bool? feed(double lux, DateTime now) {
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final want = lux <= darkAt
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? true
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: lux >= brightAt
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? false
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: _dark;
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if (_dark == null) {
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// The first clear reading decides at once; one in the gap leaves it open.
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_dark = want;
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} else if (want == _dark) {
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_since = null;
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} else {
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_since ??= now;
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if (now.difference(_since!) >= hold) {
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_dark = want;
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_since = null;
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}
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}
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return _dark;
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}
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}
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