DEBUG_TRACE (DEBUG::MackieControl, string_compose ("removing surface %1 strip %2 from down select buttons\n", surface, strip));
if (x != _down_select_buttons.end()) {
_down_select_buttons.erase (x);
DEBUG_TRACE (DEBUG::MackieControl, string_compose ("removing surface %1 strip %2 from down select buttons\n", surface, strip));
if (x != _down_select_buttons.end()) {
_down_select_buttons.erase (x);