Make Grid row/column definitions styleable

samples/ControlCatalog/Pages/SplitViewPage.xaml

@@ -56,13 +56,7 @@
                       CompactPaneLength="{Binding Value, ElementName=CompactPaneLengthSlider}"
                       DisplayMode="{Binding CurrentDisplayMode}">
           <SplitView.Pane>
-            <Grid>
-              <Grid.RowDefinitions>
-                <RowDefinition Height="Auto" />
-                <RowDefinition Height="Auto" />
-                <RowDefinition Height="*" />
-                <RowDefinition Height="Auto" />
-              </Grid.RowDefinitions>
+            <Grid RowDefinitions="Auto,Auto,*,Auto">
               <TextBlock Text="PANE CONTENT" FontWeight="Bold" Name="PaneHeader" Margin="5,12,0,0" />
               <ComboBox Width="150" Grid.Row="1">
                 <ComboBoxItem Content="Item1"/>

src/Avalonia.Controls/ColumnDefinitions.cs

@@ -39,5 +39,13 @@ public override string ToString()
         /// <param name="s">The column definitions string.</param>
         /// <returns>The <see cref="ColumnDefinitions"/>.</returns>
         public static ColumnDefinitions Parse(string s) => new ColumnDefinitions(s);
+
+        public override void UpdateParentGrid()
+        {
+            if (Parent is null) return;
+            Parent.ColIsEmpty = this.Count == 0;
+            Parent.RowOrColumnDefChanged = true;
+            Parent.Invalidate();
+        }
     }
 }

src/Avalonia.Controls/DateTimePickers/DatePicker.cs

@@ -331,7 +331,11 @@ private void SetGrid()
             };
 
             columns.Sort((x, y) => x.Item2 - y.Item2);
-            _container.ColumnDefinitions.Clear();
+
+            if (_container.ColumnDefinitions is null)
+                _container.ColumnDefinitions = new ColumnDefinitions();
+            else
+                _container.ColumnDefinitions.Clear();
 
             var columnIndex = 0;
 

src/Avalonia.Controls/DateTimePickers/DatePickerPresenter.cs

@@ -18,63 +18,63 @@ public class DatePickerPresenter : PickerPresenterBase
         /// Defines the <see cref="Date"/> Property
         /// </summary>
         public static readonly DirectProperty<DatePickerPresenter, DateTimeOffset> DateProperty =
-            AvaloniaProperty.RegisterDirect<DatePickerPresenter, DateTimeOffset>(nameof(Date), 
+            AvaloniaProperty.RegisterDirect<DatePickerPresenter, DateTimeOffset>(nameof(Date),
                 x => x.Date, (x, v) => x.Date = v);
 
         /// <summary>
         /// Defines the <see cref="DayFormat"/> Property
         /// </summary>
         public static readonly DirectProperty<DatePickerPresenter, string> DayFormatProperty =
-            DatePicker.DayFormatProperty.AddOwner<DatePickerPresenter>(x => 
+            DatePicker.DayFormatProperty.AddOwner<DatePickerPresenter>(x =>
             x.DayFormat, (x, v) => x.DayFormat = v);
 
         /// <summary>
         /// Defines the <see cref="DayVisible"/> Property
         /// </summary>
         public static readonly DirectProperty<DatePickerPresenter, bool> DayVisibleProperty =
-            DatePicker.DayVisibleProperty.AddOwner<DatePickerPresenter>(x => 
+            DatePicker.DayVisibleProperty.AddOwner<DatePickerPresenter>(x =>
             x.DayVisible, (x, v) => x.DayVisible = v);
 
         /// <summary>
         /// Defines the <see cref="MaxYear"/> Property
         /// </summary>
         public static readonly DirectProperty<DatePickerPresenter, DateTimeOffset> MaxYearProperty =
-            DatePicker.MaxYearProperty.AddOwner<DatePickerPresenter>(x => 
+            DatePicker.MaxYearProperty.AddOwner<DatePickerPresenter>(x =>
             x.MaxYear, (x, v) => x.MaxYear = v);
 
         /// <summary>
         /// Defines the <see cref="MinYear"/> Property
         /// </summary>
         public static readonly DirectProperty<DatePickerPresenter, DateTimeOffset> MinYearProperty =
-            DatePicker.MinYearProperty.AddOwner<DatePickerPresenter>(x => 
+            DatePicker.MinYearProperty.AddOwner<DatePickerPresenter>(x =>
             x.MinYear, (x, v) => x.MinYear = v);
 
         /// <summary>
         /// Defines the <see cref="MonthFormat"/> Property
         /// </summary>
         public static readonly DirectProperty<DatePickerPresenter, string> MonthFormatProperty =
-            DatePicker.MonthFormatProperty.AddOwner<DatePickerPresenter>(x => 
+            DatePicker.MonthFormatProperty.AddOwner<DatePickerPresenter>(x =>
             x.MonthFormat, (x, v) => x.MonthFormat = v);
 
         /// <summary>
         /// Defines the <see cref="MonthVisible"/> Property
         /// </summary>
         public static readonly DirectProperty<DatePickerPresenter, bool> MonthVisibleProperty =
-            DatePicker.MonthVisibleProperty.AddOwner<DatePickerPresenter>(x => 
+            DatePicker.MonthVisibleProperty.AddOwner<DatePickerPresenter>(x =>
             x.MonthVisible, (x, v) => x.MonthVisible = v);
 
         /// <summary>
         /// Defines the <see cref="YearFormat"/> Property
         /// </summary>
         public static readonly DirectProperty<DatePickerPresenter, string> YearFormatProperty =
-            DatePicker.YearFormatProperty.AddOwner<DatePickerPresenter>(x => 
+            DatePicker.YearFormatProperty.AddOwner<DatePickerPresenter>(x =>
             x.YearFormat, (x, v) => x.YearFormat = v);
 
         /// <summary>
         /// Defines the <see cref="YearVisible"/> Property
         /// </summary>
         public static readonly DirectProperty<DatePickerPresenter, bool> YearVisibleProperty =
-            DatePicker.YearVisibleProperty.AddOwner<DatePickerPresenter>(x => 
+            DatePicker.YearVisibleProperty.AddOwner<DatePickerPresenter>(x =>
             x.YearVisible, (x, v) => x.YearVisible = v);
 
         // Template Items
@@ -360,13 +360,13 @@ private void InitPicker()
                 _monthSelector.SelectedValue = dt.Month;
                 _monthSelector.FormatDate = dt.Date;
             }
-               
+
             if (YearVisible)
             {
                 _yearSelector.SelectedValue = dt.Year;
                 _yearSelector.FormatDate = dt.Date;
             }
-                
+
             _suppressUpdateSelection = false;
 
             SetInitialFocus();
@@ -383,7 +383,11 @@ private void SetGrid()
             };
 
             columns.Sort((x, y) => x.Item2 - y.Item2);
-            _pickerContainer.ColumnDefinitions.Clear();
+
+            if (_pickerContainer.ColumnDefinitions is null)
+                _pickerContainer.ColumnDefinitions = new ColumnDefinitions();
+            else
+                _pickerContainer.ColumnDefinitions.Clear();
 
             var columnIndex = 0;
 

src/Avalonia.Controls/DefinitionList.cs

@@ -13,7 +13,6 @@ public DefinitionList()
             CollectionChanged += OnCollectionChanged;
         }
 
-        internal bool IsDirty = true;
         private Grid _parent;
 
         internal Grid Parent
@@ -35,6 +34,8 @@ private void SetParent(Grid value)
 
         internal void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
         {
+            UpdateParentGrid();
+
             foreach (var nI in this.Select((d, i) => (d, i)))
                 nI.d._parentIndex = nI.i;
 
@@ -49,9 +50,12 @@ internal void OnCollectionChanged(object sender, NotifyCollectionChangedEventArg
                             ?? Enumerable.Empty<DefinitionBase>())
             {
                 oD.OnExitParentTree();
-            }
+            }            
+        }
 
-            IsDirty = true;
+
+        public virtual void UpdateParentGrid()
+        {
         }
     }
 }