Bug 573243 - Perform bulk selection instead of individually selection

Fixed append logic to bulk append selection

Change-Id: Ib92cece023514c7f7d73fef3efee2233649cfabb
diff --git a/plugins/org.eclipse.graphiti.ui/src/org/eclipse/graphiti/ui/internal/editor/GraphitiScrollingGraphicalViewer.java b/plugins/org.eclipse.graphiti.ui/src/org/eclipse/graphiti/ui/internal/editor/GraphitiScrollingGraphicalViewer.java
index 05b1772..fba9e7f 100644
--- a/plugins/org.eclipse.graphiti.ui/src/org/eclipse/graphiti/ui/internal/editor/GraphitiScrollingGraphicalViewer.java
+++ b/plugins/org.eclipse.graphiti.ui/src/org/eclipse/graphiti/ui/internal/editor/GraphitiScrollingGraphicalViewer.java
@@ -140,12 +140,20 @@
 		if (model instanceof PictogramElement) {
 			PictogramElement[] pes = tbp.getSelections((PictogramElement) model);
 			if (pes != null) {
+				List<Object> parts = new ArrayList<>();
 				for (PictogramElement pe : pes) {
 					EditPart editPart = (EditPart) getEditPartRegistry().get(pe);
 					if (editPart != null) {
-						super.appendSelection(editPart);
+						parts.add(editPart);
 					}
 				}
+				List<Object> selections = new ArrayList<>();
+				ISelection oldSelection = super.getSelection();
+				if (oldSelection instanceof IStructuredSelection) {
+					selections.addAll(((IStructuredSelection) oldSelection).toList());
+				}
+				selections.addAll(parts);
+				super.setSelection(new StructuredSelection(selections));
 			}
 		}
 	}