Updated the Default Theme Control Templates

samples/DataGridSample/MainWindow.xaml

@@ -55,7 +55,7 @@
             CellStyleClasses="gdp"/>
       
         </dg:DataGrid.Columns>
-    
+
       </dg:DataGrid>
     </TabItem>
 

src/Avalonia.DataGrid.Themes.Default/DefaultTheme.xaml

@@ -3,6 +3,7 @@
   xmlns:dg="clr-namespace:Avalonia.Controls;assembly=Avalonia.DataGrid"
   xmlns:prim="clr-namespace:Avalonia.Controls.Primitives;assembly=Avalonia.DataGrid">
 
+  <!--TODO: Validation and Focus-->
   <Style Selector="dg|DataGridCell">
     <Setter Property="Background" Value="Transparent"/>
     <Setter Property="HorizontalContentAlignment" Value="Stretch" />
@@ -101,6 +102,17 @@
                 VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
                 Margin="{TemplateBinding Padding}">
             <ContentPresenter Content="{TemplateBinding Content}"/>
+            
+            <Path Name="SortIcon"
+                  Grid.Column="1"
+                  Fill="#FF444444" 
+                  HorizontalAlignment="Left" 
+                  VerticalAlignment="Center" 
+                  Stretch="Uniform" 
+                  Width="8" 
+                  Margin="4,0,0,0" 
+                  Data="F1 M -5.215,6.099L 5.215,6.099L 0,0L -5.215,6.099 Z "/>
+          
           </Grid>
 
           <Rectangle Name="VerticalSeparator"
@@ -207,6 +219,27 @@
     <Setter Property="Opacity" Value="0.5"/>
   </Style>
   
+  <Style Selector="dg|DataGridColumnHeader /template/ Path#SortIcon">
+    <Setter Property="IsVisible" Value="False"/>
+    <Setter Property="RenderTransform">
+      <Setter.Value>
+        <ScaleTransform ScaleX="0.9" ScaleY="0.9" />
+      </Setter.Value>
+    </Setter>
+  </Style>
+  <Style Selector="dg|DataGridColumnHeader:sortascending /template/ Path#SortIcon">
+    <Setter Property="IsVisible" Value="True"/>
+  </Style>
+  <Style Selector="dg|DataGridColumnHeader:sortdescending /template/ Path#SortIcon">
+    <Setter Property="IsVisible" Value="True"/>
+    <Setter Property="RenderTransform">
+      <Setter.Value>
+        <ScaleTransform ScaleX="0.9" ScaleY="-0.9" />
+      </Setter.Value>
+    </Setter>
+  </Style>
+  
+  
   <!--FIX-->
   <Style Selector="dg|DataGridRow">
     <Setter Property="Template">
@@ -219,6 +252,7 @@
 
           <prim:DataGridRowHeader Grid.RowSpan="3" Name="PART_RowHeader" prim:DataGridFrozenGrid.IsFrozen="True" />
           <prim:DataGridCellsPresenter Grid.Column="1" Name="PART_CellsPresenter" prim:DataGridFrozenGrid.IsFrozen="True" />
+          <prim:DataGridDetailsPresenter Grid.Row="1" Grid.Column="1" Name="PART_DetailsPresenter"/>
           <Rectangle Grid.Row="2" Grid.Column="1" Name="PART_BottomGridLine" HorizontalAlignment="Stretch" Height="1" />
 
         </prim:DataGridFrozenGrid>
@@ -468,7 +502,7 @@
           
           <Rectangle Grid.Column="1" Grid.ColumnSpan="5" Fill="#FFFFFFFF" Height="1"/>
           <Rectangle Grid.Column="1" Grid.Row="1" Name="IndentSpacer" />
-          <ToggleButton Grid.Column="2" Grid.Row="1" Name="ExpanderButton" Height="15" Width="15" Margin="2,0,0,0"/>
+          <ToggleButton Grid.Column="2" Grid.Row="1" Name="ExpanderButton" Margin="2,0,0,0"/>
 
           <StackPanel Grid.Column="3" Grid.Row="1" Orientation="Horizontal" VerticalAlignment="Center" Margin="0,1,0,1">
             <TextBlock Name="PropertyNameElement" Margin="4,0,0,0" IsVisible="{TemplateBinding IsPropertyNameVisible}"/>
@@ -482,6 +516,23 @@
       </ControlTemplate>
     </Setter>
   </Style>
+  <Style Selector="dg|DataGridRowGroupHeader /template/ ToggleButton#ExpanderButton">
+    <Setter Property="Template">
+      <ControlTemplate>
+        <Border Grid.Column="0" Width="20" Height="20" Background="Transparent" HorizontalAlignment="Center" VerticalAlignment="Center">
+          <Path Fill="Black"
+                HorizontalAlignment="Center"
+                VerticalAlignment="Center"
+                Data="M 0 2 L 4 6 L 0 10 Z" />
+        </Border>
+      </ControlTemplate>
+    </Setter>
+  </Style>
+  <Style Selector="dg|DataGridRowGroupHeader /template/ ToggleButton#ExpanderButton:checked /template/ Path">
+    <Setter Property="RenderTransform">
+      <RotateTransform Angle="90" />
+    </Setter>
+  </Style>
   
   <!--
   

src/Avalonia.DataGrid/DataGridColumnHeader.cs

@@ -248,6 +248,22 @@ namespace Avalonia.Controls
                 }
             }
             */
+
+            CurrentSortingState = null;
+            if (OwningGrid != null
+                && OwningGrid.DataConnection != null
+                && OwningGrid.DataConnection.AllowSort)
+            {
+                var sort = OwningColumn.GetSortDescription();
+                if(sort != null)
+                {
+                    CurrentSortingState = sort.Descending ? ListSortDirection.Descending : ListSortDirection.Ascending;
+                }
+            }
+            PseudoClasses.Set(":sortascending", 
+                CurrentSortingState.HasValue && CurrentSortingState.Value == ListSortDirection.Ascending);
+            PseudoClasses.Set(":sortdescending", 
+                CurrentSortingState.HasValue && CurrentSortingState.Value == ListSortDirection.Descending);
         }
 
 

src/Avalonia.DataGrid/DataGridRow.cs

@@ -29,7 +29,7 @@ namespace Avalonia.Controls
 
         private const string DATAGRIDROW_elementBottomGridLine = "PART_BottomGridLine";
         private const string DATAGRIDROW_elementCells = "PART_CellsPresenter";
-        private const string DATAGRIDROW_elementDetails = "Part_DetailsPresenter";
+        private const string DATAGRIDROW_elementDetails = "PART_DetailsPresenter";
         internal const string DATAGRIDROW_elementRoot = "PART_Root";
         internal const string DATAGRIDROW_elementRowHeader = "PART_RowHeader";
 
@@ -1080,11 +1080,12 @@ namespace Avalonia.Controls
                 _previousDetailsHeight = newValue.Height;
                 if (newValue.Height != oldValue && newValue.Height != _detailsDesiredHeight)
                 {
-                    // Update the new desired height for RowDetails
-                    _detailsDesiredHeight = newValue.Height;
 
                     if (AreDetailsVisible && _appliedDetailsTemplate != null)
                     {
+                        // Update the new desired height for RowDetails
+                        _detailsDesiredHeight = newValue.Height;
+
                         //if (DetailsVisibleStoryboard != null)
                         //{
                         //    DetailsVisibleStoryboard.SkipToFill();
@@ -1097,6 +1098,10 @@ namespace Avalonia.Controls
                         // to do.  In certain scenarios, this could cause a layout cycle
                         OnRowDetailsChanged();
                     }
+                    //else if(_detailsContent != null)
+                    //{
+                    //    _detailsDesiredHeight = _detailsContent.DesiredSize.Height;
+                    //}
                 }
             }
             else