Added bottom drop border

PixiEditor/Views/MainWindow.xaml

@@ -15,8 +15,7 @@
         xmlns:avalonDockTheme="clr-namespace:PixiEditor.Styles.AvalonDock" d:DataContext="{d:DesignInstance Type=vm:ViewModelMain}"
         mc:Ignorable="d" WindowStyle="None" Initialized="MainWindow_Initialized"
         Title="PixiEditor" Name="mainWindow" Height="1000" Width="1600" Background="{StaticResource MainColor}"
-        WindowStartupLocation="CenterScreen" WindowState="Maximized"
-        AllowDrop="True" Drop="MainWindow_Drop">
+        WindowStartupLocation="CenterScreen" WindowState="Maximized">
     <WindowChrome.WindowChrome>
         <WindowChrome CaptionHeight="32"
                       ResizeBorderThickness="{x:Static SystemParameters.WindowResizeBorderThickness}" />
@@ -206,7 +205,7 @@
             </ItemsControl>
         </StackPanel>
         <Grid Grid.Column="1" Grid.Row="2" Background="#303030">
-            <Grid>
+            <Grid AllowDrop="True" Drop="MainWindow_Drop">
                 <DockingManager ActiveContent="{Binding BitmapManager.ActiveDocument, Mode=TwoWay}" 
                                            DocumentsSource="{Binding BitmapManager.Documents}">
                     <DockingManager.Theme>

PixiEditor/Views/UserControls/LayersManager.xaml

@@ -57,10 +57,11 @@
             </StackPanel>
         </DockPanel>
         <Separator Grid.Row="1" Margin="0,-12, 0, 0" BorderBrush="{StaticResource DarkerAccentColor}" BorderThickness="2" />
-        <TreeView TreeViewItem.PreviewMouseLeftButtonDown="TreeView_PreviewMouseLeftButtonDown"  Name="treeView" Grid.Row="2" Margin="0, -12, 0, 0" ItemsSource="{Binding LayerTreeRoot, ElementName=layersManager}"  SelectedItemChanged="TreeView_SelectedItemChanged">
+        <DockPanel LastChildFill="True" Grid.Row="2" Margin="0, -12, 0, 0">
+        <TreeView DockPanel.Dock="Top" TreeViewItem.PreviewMouseLeftButtonDown="TreeView_PreviewMouseLeftButtonDown" Name="treeView" ItemsSource="{Binding LayerTreeRoot, ElementName=layersManager}"  SelectedItemChanged="TreeView_SelectedItemChanged">
                 <TreeView.ItemsPanel>
                     <ItemsPanelTemplate>
-                        <ui:ReversedOrderStackPanel AllowDrop="True" Drop="ReversedOrderStackPanel_Drop"/>
+                        <ui:ReversedOrderStackPanel/>
                     </ItemsPanelTemplate>
                 </TreeView.ItemsPanel>
                 <TreeView.Resources>
@@ -81,5 +82,7 @@
                     </DataTemplate>
                 </TreeView.Resources>
             </TreeView>
+        <Border Name="dropBorder" DragEnter="Grid_DragEnter" DragLeave="Grid_DragLeave" AllowDrop="True" Drop="Grid_Drop" Background="Transparent" BorderThickness="0, 5, 0, 0"></Border>
+        </DockPanel>
     </Grid>
 </UserControl>

PixiEditor/Views/UserControls/LayersManager.xaml.cs

@@ -2,6 +2,7 @@
 using System.Collections.ObjectModel;
 using System.Windows;
 using System.Windows.Controls;
+using System.Windows.Media;
 using PixiEditor.Models.Controllers;
 using PixiEditor.Models.Layers;
 using PixiEditor.Models.Undo;
@@ -187,9 +188,47 @@ namespace PixiEditor.Views.UserControls
             }
         }
 
-        private void ReversedOrderStackPanel_Drop(object sender, DragEventArgs e)
+        private void Grid_Drop(object sender, DragEventArgs e)
         {
-            
+            dropBorder.BorderBrush = Brushes.Transparent;
+
+            if (e.Data.GetDataPresent(LayerGroupControl.LayerContainerDataName))
+            {
+                HandleLayerDrop(e.Data);
+            }
+
+            if (e.Data.GetDataPresent(LayerGroupControl.LayerGroupControlDataName))
+            {
+                HandleGroupControlDrop(e.Data);
+            }
+        }
+
+        private void HandleLayerDrop(IDataObject data)
+        {
+            var doc = LayerCommandsViewModel.Owner.BitmapManager.ActiveDocument;
+            if (doc.Layers.Count == 0) return;
+
+            var layerContainer = (LayerStructureItemContainer)data.GetData(LayerGroupControl.LayerContainerDataName);
+            var refLayer = doc.Layers[0].LayerGuid;
+            doc.MoveLayerInStructure(layerContainer.Layer.LayerGuid, refLayer);
+            doc.LayerStructure.AssignParent(layerContainer.Layer.LayerGuid, null);
+        }
+
+        private void HandleGroupControlDrop(IDataObject data)
+        {
+            var doc = LayerCommandsViewModel.Owner.BitmapManager.ActiveDocument;
+            var groupContainer = (LayerGroupControl)data.GetData(LayerGroupControl.LayerGroupControlDataName);
+            doc.LayerStructure.MoveGroup(groupContainer.GroupGuid, 0);
+        }
+
+        private void Grid_DragEnter(object sender, DragEventArgs e)
+        {
+            ((Border)sender).BorderBrush = LayerItem.HighlightColor;
+        }
+
+        private void Grid_DragLeave(object sender, DragEventArgs e)
+        {
+            ((Border)sender).BorderBrush = Brushes.Transparent;
         }
     }
 }