port from perforce

intromat/NodeNetwork/ViewModels/SelectionRectangleViewModel.cs

@@ -0,0 +1,79 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reactive.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows;
+using DynamicData;
+using ReactiveUI;
+
+namespace NodeNetwork.ViewModels
+{
+    /// <summary>
+    /// Viewmodel for the view that is used to select nodes by dragging a rectangle around them.
+    /// </summary>
+    public class SelectionRectangleViewModel : ReactiveObject
+    {
+        #region StartPoint
+        /// <summary>
+        /// The coordinates of the first corner of the rectangle (where the user clicked down).
+        /// </summary>
+        public Point StartPoint
+        {
+            get => _startPoint;
+            set => this.RaiseAndSetIfChanged(ref _startPoint, value);
+        }
+        private Point _startPoint;
+        #endregion
+
+        #region EndPoint
+        /// <summary>
+        /// The coordinates of the second corner of the rectangle.
+        /// </summary>
+        public Point EndPoint
+        {
+            get => _endPoint;
+            set => this.RaiseAndSetIfChanged(ref _endPoint, value);
+        }
+        private Point _endPoint;
+        #endregion
+
+        #region Rectangle
+        /// <summary>
+        /// The Rect object formed by StartPoint and EndPoint.
+        /// </summary>
+        public Rect Rectangle => _rectangle.Value;
+        private readonly ObservableAsPropertyHelper<Rect> _rectangle;
+        #endregion
+
+        #region IsVisible
+        /// <summary>
+        /// If true, the selection rectangle view is visible.
+        /// </summary>
+        public bool IsVisible
+        {
+            get => _isVisible;
+            set => this.RaiseAndSetIfChanged(ref _isVisible, value);
+        }
+        private bool _isVisible;
+        #endregion
+
+        #region IntersectingNodes
+        /// <summary>
+        /// List of nodes visually intersecting or contained in the rectangle.
+        /// This list is driven by the view.
+        /// </summary>
+        public ISourceList<NodeViewModel> IntersectingNodes { get; } = new SourceList<NodeViewModel>();
+        #endregion
+
+        public SelectionRectangleViewModel()
+        {
+            this.WhenAnyValue(vm => vm.StartPoint, vm => vm.EndPoint)
+                .Select(_ => new Rect(StartPoint, EndPoint))
+                .ToProperty(this, vm => vm.Rectangle, out _rectangle);
+			
+			IntersectingNodes.Connect().ActOnEveryObject(node => node.IsSelected = true, node => node.IsSelected = false);
+        }
+    }
+}