Added support for ctrl + click deselection in grid view. (#788)

Author: Dylan-Osborne

Files/UserControls/LayoutModes/PhotoAlbum.xaml

@@ -333,6 +333,7 @@
                         DataContext="{x:Bind}"
                         DataContextChanged="FileListGridItem_DataContextChanged"
                         EffectiveViewportChanged="Grid_EffectiveViewportChanged"
+                        PointerPressed="FileListGridItem_PointerPressed"
                         IsRightTapEnabled="True"
                         RightTapped="StackPanel_RightTapped"
                         Tag="ItemRoot"

Files/UserControls/LayoutModes/PhotoAlbum.xaml.cs

@@ -2,6 +2,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using Windows.Devices.Input;
 using Windows.System;
 using Windows.UI.Core;
 using Windows.UI.Xaml;
@@ -211,5 +212,27 @@ private void FileListGridItem_DataContextChanged(object sender, DataContextChang
         {
             InitializeDrag(sender as UIElement);
         }
+
+        private void FileListGridItem_PointerPressed(object sender, PointerRoutedEventArgs e)
+        {
+            if (e.KeyModifiers == VirtualKeyModifiers.Control)
+            {
+                var listedItem = (sender as Grid).DataContext as ListedItem;
+                if (FileList.SelectedItems.Contains(listedItem))
+                {
+                    FileList.SelectedItems.Remove(listedItem);
+                    // Prevent issues arising caused by the default handlers attempting to select the item that has just been deselected by ctrl + click
+                    e.Handled = true;
+                }
+            }
+            else if (e.GetCurrentPoint(sender as UIElement).Properties.IsLeftButtonPressed)
+            {
+                var listedItem = (sender as Grid).DataContext as ListedItem;
+
+                FileList.SelectedItems.Clear(); // Control not clicked, clear selected items
+                FileList.SelectedItems.Add(listedItem);
+                FileList.SelectedItem = listedItem;
+            }
+        }
     }
 }