gain_display.signal_activate().connect (sigc::mem_fun (*this, &GainMeter::gain_activated));
gain_display.signal_focus_in_event().connect (sigc::mem_fun (*this, &GainMeter::gain_focused), false);
gain_display.signal_focus_out_event().connect (sigc::mem_fun (*this, &GainMeter::gain_focused), false);
gain_display.signal_activate().connect (sigc::mem_fun (*this, &GainMeter::gain_activated));
gain_display.signal_focus_in_event().connect (sigc::mem_fun (*this, &GainMeter::gain_focused), false);
gain_display.signal_focus_out_event().connect (sigc::mem_fun (*this, &GainMeter::gain_focused), false);