增加拖放效果绘制的补偿逻辑

DeedyDesigner/Deedy.Activity/ActionViewer.cs

@@ -774,11 +774,12 @@ namespace Deedy.Activity
                 else
                 {
                     this._DropPlacement = DropPlacement.Rejected;
-                    this.RemoveDragAdorner();
+                    this.UpdateDragAdorner(this._DropPlacement);
                 }
             }
             else
             {
+                this._DropPlacement = DropPlacement.UnDragged;
                 this.RefreshViewerState();
                 this.RemoveDragAdorner();
             }

DeedyDesigner/Deedy.Activity/Helpers/VisualHelper.cs

@@ -50,6 +50,7 @@ namespace Deedy.Activity.Helpers
                             dc.DrawRectangle(brush, pen, new(0, 0, size.Width, 4));
                         else if (parentLayoutDirection == LayoutDirection.Stacked)
                             dc.DrawGeometry(brush, pen, res.DropIcon_BringForward);
+                        else break;
                     }
                     break;
                 case DropPlacement.BehindMe:
@@ -60,6 +61,7 @@ namespace Deedy.Activity.Helpers
                             dc.DrawRectangle(brush, pen, new(size.Height - 4, 0, size.Width, 4));
                         else if (parentLayoutDirection == LayoutDirection.Stacked)
                             dc.DrawGeometry(brush, pen, res.DropIcon_SendBackward);
+                        else break;
                     }
                     break;
                 case DropPlacement.WithinMe: