Nikita Tsukanov
5 years ago
16 changed files with 421 additions and 117 deletions
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using System; |
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namespace Avalonia.Utilities; |
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/// <summary>
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/// Defines a listener to a event subscribed vis the <see cref="WeakEvent{TTarget, TEventArgs}"/>.
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/// </summary>
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/// <typeparam name="TEventArgs">The type of the event arguments.</typeparam>
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public interface IWeakEventSubscriber<in TEventArgs> where TEventArgs : EventArgs |
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{ |
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void OnEvent(object? sender, WeakEvent ev, TEventArgs e); |
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} |
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using System; |
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using System.Collections.Generic; |
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using System.Linq; |
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using System.Reflection; |
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using System.Runtime.CompilerServices; |
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namespace Avalonia.Utilities; |
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/// <summary>
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/// Manages subscriptions to events using weak listeners.
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/// </summary>
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public class WeakEvent<TSender, TEventArgs> : WeakEvent where TEventArgs : EventArgs where TSender : class |
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{ |
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private readonly Func<TSender, EventHandler<TEventArgs>, Action> _subscribe; |
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readonly ConditionalWeakTable<object, Subscription> _subscriptions = new(); |
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internal WeakEvent( |
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Action<TSender, EventHandler<TEventArgs>> subscribe, |
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Action<TSender, EventHandler<TEventArgs>> unsubscribe) |
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{ |
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_subscribe = (t, s) => |
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{ |
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subscribe(t, s); |
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return () => unsubscribe(t, s); |
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}; |
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} |
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internal WeakEvent(Func<TSender, EventHandler<TEventArgs>, Action> subscribe) |
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{ |
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_subscribe = subscribe; |
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} |
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public void Subscribe(TSender target, IWeakEventSubscriber<TEventArgs> subscriber) |
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{ |
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if (!_subscriptions.TryGetValue(target, out var subscription)) |
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_subscriptions.Add(target, subscription = new Subscription(this, target)); |
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subscription.Add(new WeakReference<IWeakEventSubscriber<TEventArgs>>(subscriber)); |
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} |
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public void Unsubscribe(TSender target, IWeakEventSubscriber<TEventArgs> subscriber) |
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{ |
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if (_subscriptions.TryGetValue(target, out var subscription)) |
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subscription.Remove(subscriber); |
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} |
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private class Subscription |
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{ |
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private readonly WeakEvent<TSender, TEventArgs> _ev; |
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private readonly TSender _target; |
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private WeakReference<IWeakEventSubscriber<TEventArgs>>?[] _data = |
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new WeakReference<IWeakEventSubscriber<TEventArgs>>[16]; |
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private int _count; |
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private readonly Action _unsubscribe; |
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public Subscription(WeakEvent<TSender, TEventArgs> ev, TSender target) |
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{ |
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_ev = ev; |
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_target = target; |
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_unsubscribe = ev._subscribe(target, OnEvent); |
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} |
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void Destroy() |
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{ |
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_unsubscribe(); |
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_ev._subscriptions.Remove(_target); |
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} |
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public void Add(WeakReference<IWeakEventSubscriber<TEventArgs>> s) |
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{ |
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if (_count == _data.Length) |
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{ |
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//Extend capacity
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var extendedData = new WeakReference<IWeakEventSubscriber<TEventArgs>>?[_data.Length * 2]; |
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Array.Copy(_data, extendedData, _data.Length); |
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_data = extendedData; |
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} |
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_data[_count] = s; |
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_count++; |
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} |
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public void Remove(IWeakEventSubscriber<TEventArgs> s) |
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{ |
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var removed = false; |
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for (int c = 0; c < _count; ++c) |
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{ |
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var reference = _data[c]; |
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if (reference != null && reference.TryGetTarget(out var instance) && instance == s) |
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{ |
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_data[c] = null; |
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removed = true; |
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} |
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} |
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if (removed) |
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{ |
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Compact(); |
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} |
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} |
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void Compact() |
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{ |
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int empty = -1; |
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for (var c = 0; c < _count; c++) |
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{ |
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var r = _data[c]; |
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//Mark current index as first empty
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if (r == null && empty == -1) |
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empty = c; |
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//If current element isn't null and we have an empty one
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if (r != null && empty != -1) |
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{ |
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_data[c] = null; |
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_data[empty] = r; |
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empty++; |
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} |
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} |
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if (empty != -1) |
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_count = empty; |
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if (_count == 0) |
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Destroy(); |
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} |
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void OnEvent(object? sender, TEventArgs eventArgs) |
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{ |
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var needCompact = false; |
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for (var c = 0; c < _count; c++) |
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{ |
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var r = _data[c]; |
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if (r?.TryGetTarget(out var sub) == true) |
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sub!.OnEvent(_target, _ev, eventArgs); |
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else |
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needCompact = true; |
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} |
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if (needCompact) |
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Compact(); |
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} |
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} |
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} |
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public class WeakEvent |
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{ |
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public static WeakEvent<TSender, TEventArgs> Register<TSender, TEventArgs>( |
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Action<TSender, EventHandler<TEventArgs>> subscribe, |
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Action<TSender, EventHandler<TEventArgs>> unsubscribe) where TSender : class where TEventArgs : EventArgs |
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{ |
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return new WeakEvent<TSender, TEventArgs>(subscribe, unsubscribe); |
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} |
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public static WeakEvent<TSender, TEventArgs> Register<TSender, TEventArgs>( |
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Func<TSender, EventHandler<TEventArgs>, Action> subscribe) where TSender : class where TEventArgs : EventArgs |
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{ |
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return new WeakEvent<TSender, TEventArgs>(subscribe); |
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} |
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public static WeakEvent<TSender, EventArgs> Register<TSender>( |
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Action<TSender, EventHandler> subscribe, |
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Action<TSender, EventHandler> unsubscribe) where TSender : class |
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{ |
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return Register<TSender, EventArgs>((s, h) => |
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{ |
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EventHandler handler = (_, e) => h(s, e); |
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subscribe(s, handler); |
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return () => unsubscribe(s, handler); |
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}); |
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} |
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} |
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@ -0,0 +1,40 @@ |
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using System; |
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using System.Collections.Specialized; |
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using System.ComponentModel; |
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using System.Windows.Input; |
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namespace Avalonia.Utilities; |
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public class WeakEvents |
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{ |
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/// <summary>
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/// Represents CollectionChanged event from <see cref="INotifyCollectionChanged"/>
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/// </summary>
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public static readonly WeakEvent<INotifyCollectionChanged, NotifyCollectionChangedEventArgs> |
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CollectionChanged = WeakEvent.Register<INotifyCollectionChanged, NotifyCollectionChangedEventArgs>( |
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(c, s) => |
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{ |
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NotifyCollectionChangedEventHandler handler = (_, e) => s(c, e); |
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c.CollectionChanged += handler; |
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return () => c.CollectionChanged -= handler; |
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}); |
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/// <summary>
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/// Represents PropertyChanged event from <see cref="INotifyPropertyChanged"/>
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/// </summary>
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public static readonly WeakEvent<INotifyPropertyChanged, PropertyChangedEventArgs> |
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PropertyChanged = WeakEvent.Register<INotifyPropertyChanged, PropertyChangedEventArgs>( |
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(s, h) => |
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{ |
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PropertyChangedEventHandler handler = (_, e) => h(s, e); |
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s.PropertyChanged += handler; |
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return () => s.PropertyChanged -= handler; |
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}); |
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/// <summary>
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/// Represents CanExecuteChanged event from <see cref="ICommand"/>
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/// </summary>
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public static readonly WeakEvent<ICommand, EventArgs> CommandCanExecuteChanged = |
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WeakEvent.Register<ICommand>((s, h) => s.CanExecuteChanged += h, |
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(s, h) => s.CanExecuteChanged -= h); |
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} |
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@ -0,0 +1,75 @@ |
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using System; |
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using System.Collections.Generic; |
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using System.Linq; |
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using System.Text; |
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using System.Threading.Tasks; |
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using Avalonia.Utilities; |
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using Xunit; |
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namespace Avalonia.Base.UnitTests |
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{ |
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public class WeakEventManagerTests |
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{ |
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class EventSource |
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{ |
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public event EventHandler<EventArgs> Event; |
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public void Fire() |
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{ |
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Event?.Invoke(this, new EventArgs()); |
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} |
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public static readonly WeakEvent<EventSource, EventArgs> WeakEvent = WeakEvent<EventSource, EventArgs>.Register( |
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(t, s) => t.Event += s, |
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(t, s) => t.Event -= s); |
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} |
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class Subscriber : IWeakEventSubscriber<EventArgs> |
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{ |
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private readonly Action _onEvent; |
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public Subscriber(Action onEvent) |
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{ |
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_onEvent = onEvent; |
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} |
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public void OnEvent(object sender, WeakEvent ev, EventArgs args) |
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{ |
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_onEvent?.Invoke(); |
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} |
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} |
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[Fact] |
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public void EventShouldBePassedToSubscriber() |
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{ |
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bool handled = false; |
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var subscriber = new Subscriber(() => handled = true); |
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var source = new EventSource(); |
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EventSource.WeakEvent.Subscribe(source, subscriber); |
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source.Fire(); |
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Assert.True(handled); |
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} |
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[Fact] |
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public void EventHandlerShouldNotBeKeptAlive() |
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{ |
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bool handled = false; |
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var source = new EventSource(); |
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AddSubscriber(source, () => handled = true); |
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for (int c = 0; c < 10; c++) |
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{ |
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GC.Collect(); |
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GC.Collect(3, GCCollectionMode.Forced, true); |
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} |
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source.Fire(); |
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Assert.False(handled); |
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} |
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private void AddSubscriber(EventSource source, Action func) |
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{ |
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EventSource.WeakEvent.Subscribe(source, new Subscriber(func)); |
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} |
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} |
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} |
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