Do not modify selection if right-click is on a selected item [patch 1111174]

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@31613 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/treectlg.cpp

@@ -3176,8 +3176,14 @@ void wxGenericTreeCtrl::OnMouse( wxMouseEvent &event )
         if (item == NULL) return;  /* we hit the blank area */
 
         if ( event.RightDown() )
+        {
+            // If the item is already selected, do not update the selection.
+            // Multi-selections should not be cleared if a selected item is clicked.
+            if (!IsSelected(item))
             {
                 DoSelectItem(item, true, false);
+            }
+
             wxTreeEvent nevent(wxEVT_COMMAND_TREE_ITEM_RIGHT_CLICK, GetId());
             nevent.m_item = item;
             nevent.m_pointDrag = CalcScrolledPosition(pt);