Improved Drag+Drop & Dark Mode testing

- Drag+Drop now shows a black line where the item is going to be dropped as an additional visual cue to make it more intuitive
- Avalonia's dark default style is lacking two things:
-- Highlights on ListBoxItem are too bright (easy fix)
-- The window decoration remains white (could be disabled and replaced with custom title bar)

BFR/MainWindow.xaml

@@ -126,6 +126,18 @@
       <Setter Property="Margin" Value="4,-5,4,4"/>
     </Style>
 
+    <!-- Drag + Drop -->
+    <Style Selector="ListBoxItem.BlackBottom">
+      <Setter Property="BorderThickness" Value="0,0,0,2"/>
+      <Setter Property="BorderBrush" Value="Black"/>
+      <Setter Property="Margin" Value="0,0,0,-2"/>
+    </Style>
+    <Style Selector="ListBoxItem.BlackTop">
+      <Setter Property="BorderThickness" Value="0,2,0,0"/>
+      <Setter Property="BorderBrush" Value="Black"/>
+      <Setter Property="Margin" Value="0,-2,0,0"/>
+    </Style>
+    
     <!-- Expander Fix -->
     <Style Selector="Expander /template/ ToggleButton#PART_toggle /template/ Border">
       <Setter Property="Background" Value="Transparent"/>
@@ -160,7 +172,7 @@
                 </Grid>
               </Button.Content>
             </Button>
-            <Grid Grid.Column="3" Background="Transparent" Cursor="SizeAll" IsVisible="{Binding $parent.IsPointerOver}" ToolTip.Tip="Click and drag to move this operation." PointerPressed="StartMoveOperation" PointerReleased="EndMoveOperation">
+            <Grid Grid.Column="3" Background="Transparent" Cursor="SizeAll" IsVisible="{Binding $parent.IsPointerOver}" ToolTip.Tip="Click and drag to move this operation." PointerPressed="StartMoveOperation" PointerReleased="EndMoveOperation" PointerMoved="MoveOperation">
               <Path Data="M0,0 L12,0 M0,4 L12,4 M0,8 L12,8" Height="8" VerticalAlignment="Center" Margin="4" Stroke="Black" StrokeThickness="2"/>
             </Grid>
             <ContentPresenter Grid.ColumnSpan="4" Grid.Row="1" Content="{TemplateBinding Content}"  IsVisible="{Binding #OperationExpander.IsExpanded}"/>

BFR/MainWindow.xaml.cs

@@ -15,6 +15,7 @@ using Avalonia.LogicalTree;
 using BFR.Helpers;
 using BFR.DataModels;
 using BFR.Operations;
+using Avalonia.Markup.Xaml.Styling;
 
 namespace BFR
 {
@@ -95,22 +96,40 @@ namespace BFR
             Preview();
         }
 
+        private void ClearDropStyling()
+        {
+            foreach (ListBoxItem item in OperationsListBox.GetLogicalChildren())
+                item.Classes.RemoveAll(new[] { "BlackTop", "BlackBottom" });
+        }
+
         public void StartMoveOperation(object sender, PointerPressedEventArgs e) => 
             DragItem = OperationsListBox.GetLogicalChildren().Cast<ListBoxItem>().Single(x => x.IsPointerOver);
 
+        public void MoveOperation(object sender, PointerEventArgs e)
+        {
+            if (DragItem == null) return;
+
+            var hoveredItem = (ListBoxItem)OperationsListBox.GetLogicalChildren().FirstOrDefault(x => this.GetVisualsAt(e.GetPosition(this)).Contains(((IVisual)x).GetVisualChildren().First()));
+            var dragItemIndex = OperationsListBox.GetLogicalChildren().ToList().IndexOf(DragItem);
+            var hoveredItemIndex = OperationsListBox.GetLogicalChildren().ToList().IndexOf(hoveredItem);
+
+            ClearDropStyling();
+            if (hoveredItem != DragItem) hoveredItem?.Classes.Add(dragItemIndex > hoveredItemIndex ? "BlackTop" : "BlackBottom");
+        }
+
         public void EndMoveOperation(object sender, PointerReleasedEventArgs e)
         {
             var hoveredItem = (ListBoxItem)OperationsListBox.GetLogicalChildren().FirstOrDefault(x => this.GetVisualsAt(e.GetPosition(this)).Contains(((IVisual)x).GetVisualChildren().First()));
-            if (DragItem == null ||
+            if (DragItem != null && hoveredItem != null && DragItem != hoveredItem)
-                hoveredItem == null ||
+            {
-                DragItem == hoveredItem)
-                return;
                 Operations.Move(
                     OperationsListBox.GetLogicalChildren().ToList().IndexOf(DragItem),
                     OperationsListBox.GetLogicalChildren().ToList().IndexOf(hoveredItem));
-            DragItem = null;
                 Preview();
             }
+            ClearDropStyling();
+            DragItem = null;
+        }
 
         public void Commit()
         {
@@ -141,6 +160,12 @@ namespace BFR
             OpenDirectory(Environment.OSVersion.Platform == PlatformID.Win32NT ? @"C:/Users/" : @"/home/");
             HandleEvents = true;
             OperationsListBox = this.Find<ListBox>("OperationsListBox");
+
+            /*var dark = new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
+            {
+                Source = new Uri("resm:Avalonia.Themes.Default.Accents.BaseDark.xaml?assembly=Avalonia.Themes.Default")
+            };
+            Styles[0] = dark;/**/
         }
     }
 }