95 lines
2.8 KiB
Dart
95 lines
2.8 KiB
Dart
/*
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* Copyright (c) 2024-2026 Fabian Freund.
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*
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* This file is part of WebLibre
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* (see https://weblibre.eu).
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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import 'dart:async';
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import 'package:flutter/foundation.dart';
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/// A ValueNotifier that acts as a proxy for another ValueNotifier,
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/// sampling its values based on a given duration.
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class SampledValueNotifier<T> extends ValueNotifier<T> {
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/// The source ValueNotifier to sample from
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final ValueNotifier<T> _source;
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/// The duration to sample at
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final Duration _sampleDuration;
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/// Timer for sampling
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Timer? _timer;
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/// Whether a value has changed since the last sample
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bool _hasNewValue = false;
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/// Subscription to the source ValueNotifier
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late final VoidCallback _sourceListener;
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/// Creates a SampledValueNotifier that samples values from [source]
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/// at the specified [sampleDuration].
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SampledValueNotifier({
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required ValueNotifier<T> source,
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required Duration sampleDuration,
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}) : _source = source,
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_sampleDuration = sampleDuration,
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super(source.value) {
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// Set up listener for source changes
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_sourceListener = () {
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_hasNewValue = true;
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// Start timer if not already running
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if (_timer == null || !_timer!.isActive) {
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_startTimer();
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}
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};
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_source.addListener(_sourceListener);
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_startTimer();
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}
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/// Starts the sampling timer
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void _startTimer() {
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_timer?.cancel();
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_timer = Timer.periodic(_sampleDuration, _onSampleTime);
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}
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/// Called when it's time to sample
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void _onSampleTime(Timer timer) {
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if (_hasNewValue) {
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value = _source.value;
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_hasNewValue = false;
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}
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}
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@override
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void dispose() {
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_timer?.cancel();
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_source.removeListener(_sourceListener);
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super.dispose();
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}
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}
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extension ValueNotifierSampleExtension<T> on ValueNotifier<T> {
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/// Creates a new ValueNotifier that samples this ValueNotifier's values
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/// at the specified [duration].
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///
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/// The returned ValueNotifier must be disposed when no longer needed.
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ValueNotifier<T> sampleTime(Duration duration) {
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return SampledValueNotifier<T>(source: this, sampleDuration: duration);
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}
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}
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