Merge pull request w-ahmad#344 from godlytalias/feature/drag_selection_rectangle

Feature/drag selection rectangle

Author: w-ahmad

samples/WinUI.TableView.SampleApp/Pages/SelectionPage.xaml

@@ -36,6 +36,10 @@
                                   OnContent="True"
                                   OffContent="False"
                                   IsOn="{Binding IsReadOnly, Mode=TwoWay, ElementName=tableView}" />
+                    <ToggleSwitch Header="ShowDragRectangle"
+                                  OnContent="True"
+                                  OffContent="False"
+                                  IsOn="{Binding ShowDragRectangle, Mode=TwoWay, ElementName=tableView}" />
                     <InfoBar IsOpen="True"
                              IsClosable="False"
                              Title="Selected Item">
@@ -79,7 +83,8 @@
     ItemsSource="{Binding Items}"
     SelectionMode="$(SelectionMode)"
     SelectionUnit="$(SelectionUnit)"
-    IsReadOnly="$(IsReadOnly)" /&gt;
+    IsReadOnly="$(IsReadOnly)"
+    ShowDragRectangle="$(ShowDragRectangle)" /&gt;
                 </x:String>
             </controls:SamplePresenter.Xaml>
             <controls:SamplePresenter.Substitutions>
@@ -89,6 +94,8 @@
                                            Value="{x:Bind tableView.SelectionUnit, Mode=OneWay}" />
                 <controls:CodeSubstitution Key="IsReadOnly"
                                            Value="{x:Bind tableView.IsReadOnly, Mode=OneWay}" />
+                <controls:CodeSubstitution Key="ShowDragRectangle"
+                                           Value="{x:Bind tableView.ShowDragRectangle, Mode=OneWay}" />
             </controls:SamplePresenter.Substitutions>
         </controls:SamplePresenter>
     </Grid>

src/TableView.Properties.cs

@@ -300,6 +300,11 @@ public bool CanPaste
         set => SetValue(CanPasteProperty, value);
     }
 
+    /// <summary>
+    /// Identifies the <see cref="ShowDragRectangle"/> dependency property.
+    /// </summary>
+    public static readonly DependencyProperty ShowDragRectangleProperty = DependencyProperty.Register(nameof(ShowDragRectangle), typeof(bool), typeof(TableView), new PropertyMetadata(true, OnShowDragRectangleChanged));
+
     /// <summary>
     /// Gets or sets a value indicating whether opening the column filter over header right-click is enabled.
     /// </summary>
@@ -365,6 +370,15 @@ public bool ShowFilterItemsCount
         set => SetValue(ShowFilterItemsCountProperty, value);
     }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether the drag selection rectangle is shown during cell drag selection.
+    /// </summary>
+    public bool ShowDragRectangle
+    {
+        get => (bool)GetValue(ShowDragRectangleProperty);
+        set => SetValue(ShowDragRectangleProperty, value);
+    }
+
     /// <summary>
     /// Gets or sets a value that indicates whether the TableView should force select the Row or Cell depending on the SelectionUnit
     /// </summary>
@@ -404,6 +418,16 @@ public bool ForceRowOrCellSelectionOnContextRequested
     /// </summary>
     internal bool IsEditing { get; private set; }
 
+    /// <summary>
+    /// Gets the canvas that hosts the drag selection rectangle.
+    /// </summary>
+    internal Canvas? DragRectangleCanvas { get; private set; }
+
+    /// <summary>
+    /// Gets a value indicating whether a drag selection is currently in progress.
+    /// </summary>
+    internal bool IsDragSelecting { get; private set; }
+
     /// <summary>
     /// Gets the visibility states of details pane for each item.
     /// </summary>
@@ -928,6 +952,23 @@ private static void OnIsReadOnlyChanged(DependencyObject d, DependencyPropertyCh
         }
     }
 
+    /// <summary>
+    /// Handles changes to the ShowDragRectangle property.
+    /// </summary>
+    private static void OnShowDragRectangleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        if (d is TableView tableView && e.NewValue is false)
+        {
+            // Hide the rectangle visual but don't stop drag selection or auto-scroll
+            if (tableView._dragRectangle is not null)
+            {
+                tableView._dragRectangle.Visibility = Visibility.Collapsed;
+            }
+
+            tableView._dragStartPoint = null;
+        }
+    }
+
     /// <summary>
     /// Handles changes to the CanFilterColumns property.
     /// </summary>