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@ -2,37 +2,62 @@ |
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using System.Collections; |
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using System.Collections.Generic; |
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using System.Collections.Specialized; |
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using System.Linq; |
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using Avalonia.Controls.Utils; |
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namespace Avalonia.Controls.Selection |
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{ |
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public abstract class SelectionNodeBase<T> : ICollectionChangedListener |
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/// <summary>
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/// Base class for selection models.
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/// </summary>
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/// <typeparam name="T">The type of the element being selected.</typeparam>
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public abstract class SelectionNodeBase<T> |
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{ |
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private IEnumerable? _source; |
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private bool _rangesEnabled; |
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private List<IndexRange>? _ranges; |
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private int _collectionChanging; |
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/// <summary>
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/// Gets or sets the source collection.
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/// </summary>
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protected IEnumerable? Source |
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{ |
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get => _source; |
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set |
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{ |
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void OnPreChanged(object? sender, NotifyCollectionChangedEventArgs e) => OnSourceCollectionChangeStarted(); |
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void OnChanged(object? sender, NotifyCollectionChangedEventArgs e) => OnSourceCollectionChanged(e); |
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void OnPostChanged(object? sender, NotifyCollectionChangedEventArgs e) => OnSourceCollectionChangeFinished(); |
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if (_source != value) |
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{ |
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if (ItemsView?.Inner is INotifyCollectionChanged inccOld) |
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CollectionChangedEventManager.Instance.RemoveListener(inccOld, this); |
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if (ItemsView is not null) |
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{ |
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ItemsView.PreCollectionChanged -= OnPreChanged; |
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ItemsView.CollectionChanged -= OnChanged; |
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ItemsView.PostCollectionChanged -= OnPostChanged; |
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} |
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_source = value; |
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ItemsView = value is object ? ItemsSourceView.GetOrCreate<T>(value) : null; |
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if (ItemsView?.Inner is INotifyCollectionChanged inccNew) |
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CollectionChangedEventManager.Instance.AddListener(inccNew, this); |
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ItemsView = value is not null ? ItemsSourceView.GetOrCreate<T>(value) : null; |
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if (ItemsView is not null) |
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{ |
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ItemsView.PreCollectionChanged += OnPreChanged; |
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ItemsView.CollectionChanged += OnChanged; |
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ItemsView.PostCollectionChanged += OnPostChanged; |
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} |
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} |
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} |
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} |
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protected bool IsSourceCollectionChanging => _collectionChanging > 0; |
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/// <summary>
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/// Gets an <see cref="ItemsSourceView{T}"/> of the <see cref="Source"/>.
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/// </summary>
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protected internal ItemsSourceView<T>? ItemsView { get; set; } |
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/// <summary>
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/// Gets or sets a value indicating whether range selection is currently enabled for
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/// the selection node.
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/// </summary>
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protected bool RangesEnabled |
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{ |
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get => _rangesEnabled; |
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@ -50,8 +75,6 @@ namespace Avalonia.Controls.Selection |
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} |
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} |
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internal ItemsSourceView<T>? ItemsView { get; set; } |
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internal IReadOnlyList<IndexRange> Ranges |
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{ |
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get |
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@ -65,81 +88,170 @@ namespace Avalonia.Controls.Selection |
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} |
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} |
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void ICollectionChangedListener.PreChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e) |
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/// <summary>
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/// Called when the source collection starts changing.
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/// </summary>
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protected virtual void OnSourceCollectionChangeStarted() |
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{ |
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++_collectionChanging; |
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} |
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void ICollectionChangedListener.Changed(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e) |
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/// <summary>
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/// Called when the <see cref="Source"/> collection changes.
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/// </summary>
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/// <param name="e">The details of the collection change.</param>
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/// <remarks>
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/// The implementation in <see cref="SelectionNodeBase{T}"/> calls
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/// <see cref="OnItemsAdded(int, IList)"/> and <see cref="OnItemsRemoved(int, IList)"/>
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/// in order to calculate how the collection change affects the currently selected items.
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/// It then calls <see cref="OnIndexesChanged(int, int)"/> and
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/// <see cref="OnSelectionRemoved(int, int, IReadOnlyList{T})"/> if necessary, according
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/// to the <see cref="CollectionChangeState"/> returned by those methods.
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///
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/// Override this method and <see cref="OnSourceCollectionChangeFinished"/> to provide
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/// custom handling of source collection changes.
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/// </remarks>
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protected virtual void OnSourceCollectionChanged(NotifyCollectionChangedEventArgs e) |
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{ |
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OnSourceCollectionChanged(e); |
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} |
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var shiftDelta = 0; |
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var shiftIndex = -1; |
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List<T>? removed = null; |
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void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e) |
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{ |
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if (--_collectionChanging == 0) |
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if (!IsValidCollectionChange(e)) |
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{ |
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OnSourceCollectionChangeFinished(); |
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return; |
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} |
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} |
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protected abstract void OnSourceCollectionChangeFinished(); |
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private protected abstract void OnIndexesChanged(int shiftIndex, int shiftDelta); |
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private protected abstract void OnSourceReset(); |
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private protected abstract void OnSelectionChanged(IReadOnlyList<T> deselectedItems); |
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private protected int CommitSelect(IndexRange range) |
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{ |
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if (RangesEnabled) |
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switch (e.Action) |
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{ |
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_ranges ??= new List<IndexRange>(); |
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return IndexRange.Add(_ranges, range); |
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case NotifyCollectionChangedAction.Add: |
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{ |
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var change = OnItemsAdded(e.NewStartingIndex, e.NewItems!); |
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shiftIndex = change.ShiftIndex; |
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shiftDelta = change.ShiftDelta; |
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break; |
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} |
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case NotifyCollectionChangedAction.Remove: |
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{ |
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var change = OnItemsRemoved(e.OldStartingIndex, e.OldItems!); |
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shiftIndex = change.ShiftIndex; |
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shiftDelta = change.ShiftDelta; |
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removed = change.RemovedItems; |
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break; |
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} |
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case NotifyCollectionChangedAction.Replace: |
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case NotifyCollectionChangedAction.Move: |
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{ |
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var removeChange = OnItemsRemoved(e.OldStartingIndex, e.OldItems!); |
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var addChange = OnItemsAdded(e.NewStartingIndex, e.NewItems!); |
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shiftIndex = removeChange.ShiftIndex; |
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shiftDelta = removeChange.ShiftDelta + addChange.ShiftDelta; |
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removed = removeChange.RemovedItems; |
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} |
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break; |
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case NotifyCollectionChangedAction.Reset: |
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OnSourceReset(); |
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break; |
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} |
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return 0; |
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if (shiftDelta != 0) |
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OnIndexesChanged(shiftIndex, shiftDelta); |
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if (removed is not null) |
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OnSelectionRemoved(shiftIndex, -shiftDelta, removed); |
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} |
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private protected int CommitSelect(IReadOnlyList<IndexRange> ranges) |
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/// <summary>
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/// Called when the source collection has finished changing, and all CollectionChanged
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/// handlers have run.
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/// </summary>
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/// <remarks>
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/// Override this method to respond to the end of a collection change instead of acting at
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/// the end of <see cref="OnSourceCollectionChanged(NotifyCollectionChangedEventArgs)"/>
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/// in order to ensure that all UI subscribers to the source collection change event have
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/// had chance to run.
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/// </remarks>
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protected virtual void OnSourceCollectionChangeFinished() |
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{ |
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if (RangesEnabled) |
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{ |
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_ranges ??= new List<IndexRange>(); |
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return IndexRange.Add(_ranges, ranges); |
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} |
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} |
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return 0; |
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/// <summary>
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/// Called by <see cref="OnSourceCollectionChanged(NotifyCollectionChangedEventArgs)"/>,
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/// detailing the indexes changed by the collection changing.
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/// </summary>
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/// <param name="shiftIndex">The first index that was shifted.</param>
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/// <param name="shiftDelta">
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/// If positive, the number of items inserted, or if negative the number of items removed.
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/// </param>
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protected virtual void OnIndexesChanged(int shiftIndex, int shiftDelta) |
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{ |
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} |
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/// <summary>
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/// Called by <see cref="OnSourceCollectionChanged(NotifyCollectionChangedEventArgs)"/>,
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/// on collection reset.
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/// </summary>
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protected abstract void OnSourceReset(); |
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/// <summary>
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/// Called by <see cref="OnSourceCollectionChanged(NotifyCollectionChangedEventArgs)"/>,
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/// detailing the items removed by a collection change.
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/// </summary>
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protected virtual void OnSelectionRemoved(int index, int count, IReadOnlyList<T> deselectedItems) |
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{ |
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} |
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private protected int CommitDeselect(IndexRange range) |
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/// <summary>
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/// If <see cref="RangesEnabled"/>, adds the specified range to the selection.
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/// </summary>
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/// <param name="begin">The inclusive index of the start of the range to select.</param>
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/// <param name="end">The inclusive index of the end of the range to select.</param>
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/// <returns>The number of items selected.</returns>
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protected int CommitSelect(int begin, int end) |
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{ |
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if (RangesEnabled) |
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{ |
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_ranges ??= new List<IndexRange>(); |
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return IndexRange.Remove(_ranges, range); |
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return IndexRange.Add(_ranges, new IndexRange(begin, end)); |
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} |
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return 0; |
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} |
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private protected int CommitDeselect(IReadOnlyList<IndexRange> ranges) |
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/// <summary>
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/// If <see cref="RangesEnabled"/>, removes the specified range from the selection.
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/// </summary>
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/// <param name="begin">The inclusive index of the start of the range to deselect.</param>
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/// <param name="end">The inclusive index of the end of the range to deselect.</param>
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/// <returns>The number of items selected.</returns>
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protected int CommitDeselect(int begin, int end) |
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{ |
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if (RangesEnabled && _ranges is object) |
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if (RangesEnabled) |
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{ |
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return IndexRange.Remove(_ranges, ranges); |
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_ranges ??= new List<IndexRange>(); |
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return IndexRange.Remove(_ranges, new IndexRange(begin, end)); |
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} |
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return 0; |
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} |
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private protected virtual CollectionChangeState OnItemsAdded(int index, IList items) |
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/// <summary>
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/// Called by <see cref="OnSourceCollectionChanged(NotifyCollectionChangedEventArgs)"/>
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/// when items are added to the source collection.
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/// </summary>
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/// <returns>
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/// A <see cref="CollectionChangeState"/> struct containing the details of the adjusted
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/// selection.
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/// </returns>
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/// <remarks>
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/// The implementation in <see cref="SelectionNodeBase{T}"/> adjusts the selected ranges,
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/// assigning new indexes. Override this method to carry out additional computation when
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/// items are added.
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/// </remarks>
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protected virtual CollectionChangeState OnItemsAdded(int index, IList items) |
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{ |
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var count = items.Count; |
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var shifted = false; |
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if (_ranges is object) |
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if (_ranges is not null) |
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{ |
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List<IndexRange>? toAdd = null; |
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@ -150,7 +262,7 @@ namespace Avalonia.Controls.Selection |
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// The range is after the inserted items, need to shift the range right
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if (range.End >= index) |
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{ |
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int begin = range.Begin; |
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var begin = range.Begin; |
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// If the index left of newIndex is inside the range,
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// Split the range and remember the left piece to add later
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@ -167,7 +279,7 @@ namespace Avalonia.Controls.Selection |
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} |
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} |
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if (toAdd is object) |
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if (toAdd is not null) |
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{ |
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foreach (var range in toAdd) |
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{ |
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@ -183,14 +295,27 @@ namespace Avalonia.Controls.Selection |
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}; |
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} |
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/// <summary>
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/// Called by <see cref="OnSourceCollectionChanged(NotifyCollectionChangedEventArgs)"/>
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/// when items are removed from the source collection.
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/// </summary>
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/// <returns>
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/// A <see cref="CollectionChangeState"/> struct containing the details of the adjusted
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/// selection.
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/// </returns>
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/// <remarks>
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/// The implementation in <see cref="SelectionNodeBase{T}"/> adjusts the selected ranges,
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/// assigning new indexes. Override this method to carry out additional computation when
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/// items are removed.
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/// </remarks>
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private protected virtual CollectionChangeState OnItemsRemoved(int index, IList items) |
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{ |
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var count = items.Count; |
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var removedRange = new IndexRange(index, index + count - 1); |
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bool shifted = false; |
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var shifted = false; |
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List<T>? removed = null; |
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if (_ranges is object) |
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if (_ranges is not null) |
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{ |
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var deselected = new List<IndexRange>(); |
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@ -227,60 +352,6 @@ namespace Avalonia.Controls.Selection |
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}; |
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} |
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private protected virtual void OnSourceCollectionChanged(NotifyCollectionChangedEventArgs e) |
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{ |
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var shiftDelta = 0; |
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var shiftIndex = -1; |
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List<T>? removed = null; |
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if (!IsValidCollectionChange(e)) |
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{ |
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return; |
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} |
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switch (e.Action) |
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{ |
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case NotifyCollectionChangedAction.Add: |
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{ |
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var change = OnItemsAdded(e.NewStartingIndex, e.NewItems!); |
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shiftIndex = change.ShiftIndex; |
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shiftDelta = change.ShiftDelta; |
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break; |
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} |
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case NotifyCollectionChangedAction.Remove: |
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{ |
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var change = OnItemsRemoved(e.OldStartingIndex, e.OldItems!); |
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shiftIndex = change.ShiftIndex; |
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shiftDelta = change.ShiftDelta; |
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removed = change.RemovedItems; |
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break; |
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} |
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case NotifyCollectionChangedAction.Replace: |
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case NotifyCollectionChangedAction.Move: |
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{ |
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var removeChange = OnItemsRemoved(e.OldStartingIndex, e.OldItems!); |
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var addChange = OnItemsAdded(e.NewStartingIndex, e.NewItems!); |
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shiftIndex = removeChange.ShiftIndex; |
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shiftDelta = removeChange.ShiftDelta + addChange.ShiftDelta; |
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removed = removeChange.RemovedItems; |
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} |
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break; |
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case NotifyCollectionChangedAction.Reset: |
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OnSourceReset(); |
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break; |
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} |
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if (shiftDelta != 0) |
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{ |
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OnIndexesChanged(shiftIndex, shiftDelta); |
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} |
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if (removed is object) |
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{ |
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OnSelectionChanged(removed); |
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} |
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} |
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private protected virtual bool IsValidCollectionChange(NotifyCollectionChangedEventArgs e) |
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{ |
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// If the selection is modified in a CollectionChanged handler before the selection
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@ -309,11 +380,27 @@ namespace Avalonia.Controls.Selection |
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return true; |
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} |
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private protected struct CollectionChangeState |
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/// <summary>
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/// Details the results of a collection change on the current selection;
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/// </summary>
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protected class CollectionChangeState |
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{ |
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public int ShiftIndex; |
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public int ShiftDelta; |
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public List<T>? RemovedItems; |
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/// <summary>
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/// Gets or sets the first index that was shifted as a result of the collection
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/// changing.
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/// </summary>
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public int ShiftIndex { get; set; } |
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/// <summary>
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/// Gets or sets a value indicating how the indexes after <see cref="ShiftIndex"/>
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/// were shifted.
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/// </summary>
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public int ShiftDelta { get; set; } |
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/// <summary>
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/// Gets or sets the items removed by the collection change, if any.
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/// </summary>
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public List<T>? RemovedItems { get; set; } |
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} |
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} |
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} |
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Steven Kirk
3 years ago
GitHub