Merge branch 'master' into FixReadOnlyCaretVisibility

src/Avalonia.Controls/Grid.cs

@@ -194,6 +194,16 @@ namespace Avalonia.Controls
         /// </summary>
         private GridLayout.MeasureResult _rowMeasureCache;
 
+        /// <summary>
+        /// Gets the row layout as of the last measure.
+        /// </summary>
+        private GridLayout _rowLayoutCache;
+
+        /// <summary>
+        /// Gets the column layout as of the last measure.
+        /// </summary>
+        private GridLayout _columnLayoutCache;
+
         /// <summary>
         /// Measures the grid.
         /// </summary>
@@ -253,6 +263,9 @@ namespace Avalonia.Controls
             // Cache the measure result and return the desired size.
             _columnMeasureCache = columnResult;
             _rowMeasureCache = rowResult;
+            _rowLayoutCache = rowLayout;
+            _columnLayoutCache = columnLayout;
+
             return new Size(columnResult.DesiredLength, rowResult.DesiredLength);
 
             // Measure each child only once.
@@ -299,13 +312,11 @@ namespace Avalonia.Controls
             //       arrow back to any statements and re-run them without any side-effect.
 
             var (safeColumns, safeRows) = GetSafeColumnRows();
-            var columnLayout = new GridLayout(ColumnDefinitions);
-            var rowLayout = new GridLayout(RowDefinitions);
-
+            var columnLayout = _columnLayoutCache;
+            var rowLayout = _rowLayoutCache;
             // Calculate for arrange result.
             var columnResult = columnLayout.Arrange(finalSize.Width, _columnMeasureCache);
             var rowResult = rowLayout.Arrange(finalSize.Height, _rowMeasureCache);
-
             // Arrange the children.
             foreach (var child in Children.OfType<Control>())
             {
@@ -315,7 +326,6 @@ namespace Avalonia.Controls
                 var y = Enumerable.Range(0, row).Sum(r => rowResult.LengthList[r]);
                 var width = Enumerable.Range(column, columnSpan).Sum(c => columnResult.LengthList[c]);
                 var height = Enumerable.Range(row, rowSpan).Sum(r => rowResult.LengthList[r]);
-
                 child.Arrange(new Rect(x, y, width, height));
             }
 

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -360,7 +360,7 @@ namespace Avalonia.Controls.Primitives
                     {
                         if (!AlwaysSelected)
                         {
-                            SelectedIndex = -1;
+                            selectedIndex = SelectedIndex = -1;
                         }
                         else
                         {
@@ -368,6 +368,11 @@ namespace Avalonia.Controls.Primitives
                         }
                     }
 
+                    var items = Items?.Cast<object>();
+                    if (selectedIndex >= items.Count())
+                    {
+                        selectedIndex = SelectedIndex = items.Count() - 1;
+                    }
                     break;
 
                 case NotifyCollectionChangedAction.Reset:

tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs

@@ -149,6 +149,34 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.Equal(1, target.SelectedIndex);
         }
 
+        [Fact]
+        public void SelectedIndex_Item_Is_Updated_As_Items_Removed_When_Last_Item_Is_Selected()
+        {
+            var items = new ObservableCollection<string>
+            {
+               "Foo",
+               "Bar",
+               "FooBar"
+            };
+
+            var target = new SelectingItemsControl
+            {
+                Items = items,
+                Template = Template(),
+            };
+
+            target.ApplyTemplate();
+            target.SelectedItem = items[2];
+
+            Assert.Equal(items[2], target.SelectedItem);
+            Assert.Equal(2, target.SelectedIndex);
+
+            items.RemoveAt(0);
+
+            Assert.Equal(items[1], target.SelectedItem);
+            Assert.Equal(1, target.SelectedIndex);
+        }
+
         [Fact]
         public void Setting_SelectedItem_To_Not_Present_Item_Should_Clear_Selection()
         {