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