Implement canceling edits in FZE, fix crashes related to canceling. (#1610)

* Implemented proper canceling for CanvasEditor

* Implemented proper canceling for GridEditor

* Possible fix for a crash in my implementation of canceling

* Fixed a crash in FZE/Grid editor

src/modules/fancyzones/editor/FancyZonesEditor/CanvasEditor.xaml.cs

@@ -55,6 +55,12 @@ namespace FancyZonesEditor
                 previewChildrenCount++;
             }
 
+            while (previewChildrenCount > _model.Zones.Count)
+            {
+                Preview.Children.RemoveAt(previewChildrenCount - 1);
+                previewChildrenCount--;
+            }
+
             for (int i = 0; i < previewChildrenCount; i++)
             {
                 Int32Rect rect = _model.Zones[i];

src/modules/fancyzones/editor/FancyZonesEditor/CanvasEditorWindow.xaml.cs

@@ -16,6 +16,7 @@ namespace FancyZonesEditor
         {
             InitializeComponent();
             _model = EditorOverlay.Current.DataContext as CanvasLayoutModel;
+            _stashedModel = (CanvasLayoutModel)_model.Clone();
         }
 
         private void OnAddZone(object sender, RoutedEventArgs e)
@@ -24,7 +25,14 @@ namespace FancyZonesEditor
             _offset += 100;
         }
 
+        protected new void OnCancel(object sender, RoutedEventArgs e)
+        {
+            base.OnCancel(sender, e);
+            _stashedModel.RestoreTo(_model);
+        }
+
         private int _offset = 100;
         private CanvasLayoutModel _model;
+        private CanvasLayoutModel _stashedModel;
     }
 }

src/modules/fancyzones/editor/FancyZonesEditor/GridEditor.xaml.cs

@@ -18,11 +18,16 @@ namespace FancyZonesEditor
     {
         public static readonly DependencyProperty ModelProperty = DependencyProperty.Register("Model", typeof(GridLayoutModel), typeof(GridEditor), new PropertyMetadata(null, OnGridDimensionsChanged));
 
+        private static int gridEditorUniqueIdCounter = 0;
+
+        private int gridEditorUniqueId;
+
         public GridEditor()
         {
             InitializeComponent();
             Loaded += GridEditor_Loaded;
             ((App)Application.Current).ZoneSettings.PropertyChanged += ZoneSettings_PropertyChanged;
+            gridEditorUniqueId = ++gridEditorUniqueIdCounter;
         }
 
         private void GridEditor_Loaded(object sender, RoutedEventArgs e)
@@ -73,7 +78,9 @@ namespace FancyZonesEditor
         private void ZoneSettings_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
         {
             Size actualSize = new Size(ActualWidth, ActualHeight);
-            if (actualSize.Width > 0)
+
+            // Only enter if this is the newest instance
+            if (actualSize.Width > 0 && gridEditorUniqueId == gridEditorUniqueIdCounter)
             {
                 ArrangeGridRects(actualSize);
             }
@@ -495,7 +502,8 @@ namespace FancyZonesEditor
 
         private void OnGridDimensionsChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
         {
-            if ((e.PropertyName == "Rows") || (e.PropertyName == "Columns"))
+            // Only enter if this is the newest instance
+            if (((e.PropertyName == "Rows") || (e.PropertyName == "Columns")) && gridEditorUniqueId == gridEditorUniqueIdCounter)
             {
                 OnGridDimensionsChanged();
             }

src/modules/fancyzones/editor/FancyZonesEditor/GridEditorWindow.xaml.cs

@@ -2,6 +2,9 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Windows;
+using FancyZonesEditor.Models;
+
 namespace FancyZonesEditor
 {
     /// <summary>
@@ -12,6 +15,16 @@ namespace FancyZonesEditor
         public GridEditorWindow()
         {
             InitializeComponent();
+            _stashedModel = (GridLayoutModel)(EditorOverlay.Current.DataContext as GridLayoutModel).Clone();
         }
+
+        protected new void OnCancel(object sender, RoutedEventArgs e)
+        {
+            base.OnCancel(sender, e);
+            GridLayoutModel model = EditorOverlay.Current.DataContext as GridLayoutModel;
+            _stashedModel.RestoreTo(model);
+        }
+
+        private GridLayoutModel _stashedModel;
     }
 }

src/modules/fancyzones/editor/FancyZonesEditor/Models/CanvasLayoutModel.cs

@@ -113,6 +113,15 @@ namespace FancyZonesEditor.Models
             return layout;
         }
 
+        public void RestoreTo(CanvasLayoutModel other)
+        {
+            other.Zones.Clear();
+            foreach (Int32Rect zone in Zones)
+            {
+                other.Zones.Add(zone);
+            }
+        }
+
         // PersistData
         // Implements the LayoutModel.PersistData abstract method
         protected override void PersistData()

src/modules/fancyzones/editor/FancyZonesEditor/Models/GridLayoutModel.cs

@@ -131,6 +131,12 @@ namespace FancyZonesEditor.Models
         public override LayoutModel Clone()
         {
             GridLayoutModel layout = new GridLayoutModel(Name);
+            RestoreTo(layout);
+            return layout;
+        }
+
+        public void RestoreTo(GridLayoutModel layout)
+        {
             int rows = Rows;
             int cols = Columns;
 
@@ -163,8 +169,6 @@ namespace FancyZonesEditor.Models
             }
 
             layout.ColumnPercents = colPercents;
-
-            return layout;
         }
 
         // PersistData