Auto show popup after Next Change or Previous Change command

GitDiffMargin/View/EditorDiffMarginControl.xaml

@@ -118,8 +118,9 @@
             <Popup AllowsTransparency="True"
                    HorizontalOffset="8"
                    IsOpen="{Binding ShowPopup, Mode=TwoWay}"
-                   Placement="MousePoint"
+                   Placement="Custom"
                    PlacementTarget="{Binding ElementName=diffControl}"
+                   CustomPopupPlacementCallback="HandleCustomPopupPlacement"
                    StaysOpen="False">
               <Border Background="Transparent">
                 <StackPanel Orientation="Vertical">

GitDiffMargin/View/EditorDiffMarginControl.xaml.cs

@@ -1,5 +1,8 @@
 namespace GitDiffMargin.View
 {
+    using System.Windows;
+    using System.Windows.Controls.Primitives;
+
     /// <summary>
     ///   Interaction logic for EditorDiffMarginControl.xaml
     /// </summary>
@@ -9,5 +12,14 @@ public EditorDiffMarginControl()
         {
             InitializeComponent();
         }
+
+        private CustomPopupPlacement[] HandleCustomPopupPlacement(Size popupSize, Size targetSize, Point offset)
+        {
+            // TODO: Change vertical placement to be relative to mouse position IFF the mouse is vertically within the
+            // target diff glyph.
+            CustomPopupPlacement verticalPlacement = new CustomPopupPlacement(offset, PopupPrimaryAxis.Vertical);
+            CustomPopupPlacement horizontalPlacement = new CustomPopupPlacement(offset, PopupPrimaryAxis.Horizontal);
+            return new[] { verticalPlacement, horizontalPlacement };
+        }
     }
 }

GitDiffMargin/ViewModel/EditorDiffMarginViewModel.cs

@@ -64,6 +64,7 @@ private void MoveToChange(DiffViewModel currentDiffViewModel, int indexModifier)
             MarginCore.MoveToChange(diffViewModel.LineNumber);    
 
             ((EditorDiffViewModel)currentDiffViewModel).ShowPopup = false;
+            ((EditorDiffViewModel)diffViewModel).ShowPopUpCommand.Execute(this);
         }
 
         protected override void HandleHunksChanged(object sender, HunksChangedEventArgs e)