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| public class TestBehavior : Behavior<ListBox>
{
enum SelectionMode
{
None,
New,
Add,
Multi
}
ListBox? listBox;
Canvas? _canvas;
readonly Border _selectionRectangle = new()
{
BorderBrush = Brushes.Blue,
BorderThickness = new Thickness(1),
Background = new SolidColorBrush(Colors.LightBlue, 0.3),
IsHitTestVisible = false,
IsVisible = false
};
SelectionMode _mode = SelectionMode.None;
bool _isSelecting;
Point _startPoint;
HashSet<object> _initialSelection = new();
HashSet<object> newSelection = new();
protected override void OnAttached()
{
base.OnAttached();
if (AssociatedObject is not ListBox) throw new ArgumentException("AssociatedObject is null or is not Type of Listbox");
listBox = AssociatedObject;
listBox.PointerPressed += OnPointerPressedEvent;
listBox.PointerMoved += OnPointerMoved;
listBox.PointerReleased += OnPointerReleased;
var scrollViewer = listBox.FindAncestorOfType<ScrollViewer>();
if (scrollViewer != null)
{
scrollViewer.ScrollChanged += OnScrollChanged;
}
Grid? ct = listBox.Parent as Grid ?? throw new ArgumentException("AssociatedObject is not in a Grid");
_canvas = ct.Children[0] as Canvas ?? throw new ArgumentException("AssociatedObject has not a canvas");
_canvas.Children.Add(_selectionRectangle);
}
protected override void OnDetaching()
{
if (_canvas is not null) _canvas = null;
if (listBox is not null)
{
var scrollViewer = listBox.FindAncestorOfType<ScrollViewer>();
if (scrollViewer != null)
{
scrollViewer.ScrollChanged -= OnScrollChanged;
}
listBox.PointerPressed -= OnPointerPressedEvent;
listBox.PointerMoved -= OnPointerMoved;
listBox.PointerReleased -= OnPointerReleased;
}
base.OnDetaching();
}
void OnScrollChanged(object? sender, ScrollChangedEventArgs e)
{
if (_canvas is null || listBox is null) return;
var scrollViewer = sender as ScrollViewer;
if (scrollViewer is null) return;
var offsetY = scrollViewer.Offset.Y;
// Mise à jour de la position du rectangle de sélection
var currentTop = Canvas.GetTop(_selectionRectangle);
Canvas.SetTop(_selectionRectangle, _startPoint.Y - offsetY);
}
void OnPointerPressedEvent(object? sender, PointerPressedEventArgs e)
{
if (!e.GetCurrentPoint(listBox).Properties.IsLeftButtonPressed) return;
if (listBox is null || _canvas is null) return;
SetMode(e.KeyModifiers);
_startPoint = e.GetPosition(_canvas);
_selectionRectangle.Width = 0;
_selectionRectangle.Height = 0;
Canvas.SetLeft(_selectionRectangle, _startPoint.X);
Canvas.SetTop(_selectionRectangle, _startPoint.Y);
}
void OnPointerMoved(object? sender, PointerEventArgs e)
{
if (!_isSelecting || listBox is null || _canvas is null) return;
if (!e.GetCurrentPoint(listBox).Properties.IsLeftButtonPressed) return;
var pointerPosition = e.GetPosition(listBox);
_selectionRectangle.IsVisible = true;
var endPoint = e.GetPosition(_canvas);
double x = Math.Min(_startPoint.X, endPoint.X);
double y = Math.Min(_startPoint.Y, endPoint.Y);
double width = Math.Abs(endPoint.X - _startPoint.X);
double height = Math.Abs(endPoint.Y - _startPoint.Y);
Canvas.SetLeft(_selectionRectangle, x);
Canvas.SetTop(_selectionRectangle, y);
_selectionRectangle.Width = width;
_selectionRectangle.Height = height;
SelectItems(listBox, new Rect(x, y, width, height));
}
void OnPointerReleased(object? sender, PointerReleasedEventArgs e)
{
_isSelecting = false;
_selectionRectangle.IsVisible = false;
_initialSelection.Clear();
newSelection.Clear();
}
void SetMode(KeyModifiers key)
{
_isSelecting = true;
if (key.HasFlag(KeyModifiers.Control))
{
_mode = SelectionMode.Multi;
}
else if (key.HasFlag(KeyModifiers.Shift))
{
_mode = SelectionMode.Add;
}
else
{
_mode = SelectionMode.New;
listBox?.SelectedItems?.Clear();
}
}
private void SelectItems(ListBox listBox, Rect selectionBounds)
{
if (listBox is null || _canvas is null) return;
var scrollViewer = listBox.FindAncestorOfType<ScrollViewer>();
var scrollOffset = scrollViewer?.Offset.Y ?? 0;
foreach (var item in listBox.Items)
{
var container = listBox.ContainerFromItem(item) as Control;
if (container == null) continue;
var itemBounds = new Rect(container.TranslatePoint(new Point(0, 0), _canvas) ?? new Point(), container.Bounds.Size);
itemBounds = new Rect(itemBounds.X, itemBounds.Y - scrollOffset, itemBounds.Width, itemBounds.Height);
bool isInside = selectionBounds.Intersects(itemBounds);
switch (_mode)
{
case SelectionMode.New:
if (isInside)
{
if (!listBox.SelectedItems.Contains(item))
{
listBox.SelectedItems.Add(item);
}
}
else
{
if (listBox.SelectedItems.Contains(item))
{
listBox.SelectedItems.Remove(item);
}
}
break;
case SelectionMode.Add:
if (isInside && !listBox.SelectedItems.Contains(item))
{
listBox.SelectedItems.Add(item);
}
break;
case SelectionMode.Multi:
if (isInside)
{
if (listBox.SelectedItems.Contains(item))
{
listBox.SelectedItems.Remove(item);
}
else
{
listBox.SelectedItems.Add(item);
}
}
break;
}
}
}
} |
WPF/Avalonia : Selection par lasso
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