adjust logic for slaved faders, not necessarily correctly.

More info in the code comments.

diff --git a/gtk2_ardour/gain_meter.cc b/gtk2_ardour/gain_meter.cc
index 483fa61bd55a7b1991a76223e232b5120e702e75..d6ca97b425bb8015d1a1c4d3dc209c8bc11c9db0 100644 (file)
--- a/gtk2_ardour/gain_meter.cc
+++ b/gtk2_ardour/gain_meter.cc
@@ -523,19 +523,57 @@ GainMeterBase::show_gain ()
 void
 GainMeterBase::fader_moved ()
 {
-       gain_t value;
-       const gain_t master_gain = _control->get_master_gain ();
+       if (!ignore_toggle) {
 
-       /* convert from adjustment range (0..1) to gain coefficient */
+               gain_t value;
+               const gain_t master_gain = _control->get_master_gain ();
 
-       if (_data_type == DataType::AUDIO) {
-               value = slider_position_to_gain_with_max (gain_adjustment.get_value(), Config->get_max_gain()) / master_gain;
-       } else {
-               value = gain_adjustment.get_value();
-       }
+               /* convert from adjustment range (0..1) to gain coefficient */
 
-       if (!ignore_toggle) {
-               if (_route && _route->amp() == _amp) {
+               if (_data_type == DataType::AUDIO) {
+
+                       if (_control->slaved ()) {
+
+                               /* fader has been moved. The initial position of the fader
+                                  reflects any master gain (see ::gain_changed() below). So
+                                  when we reset the actual gain value, we have to remove the
+                                  influence of the master gain (if any).
+
+                                  but ... the fader is non-linear. a given number of dB will have a
+                                  relatively small effect on fader position far from the 0dB
+                                  position, and a larger effect near to it.
+
+                                  so... we take the current gain value, and compute where the
+                                  fader was BEFORE it was moved. Then we compute how the
+                                  position delta that the master gain caused.
+
+                                  once we have that value, we subtract it from the current
+                                  fader position, which gives us the current fader position as
+                                  if there was no master.
+                               */
+
+                               const gain_t current_value = _control->get_value (); /* current value */
+                               const float position_delta_caused_by_master = gain_to_slider_position_with_max (current_value * master_gain, Config->get_max_gain()) -
+                                       gain_to_slider_position_with_max (current_value, Config->get_max_gain());
+
+                               /* this is "where would the fader be now if the master
+                                  wan't changing things?"
+                               */
+
+                               const float adjusted_position = min (gain_adjustment.get_upper(), max (gain_adjustment.get_lower(), gain_adjustment.get_value() - position_delta_caused_by_master));
+
+                               value = slider_position_to_gain_with_max (adjusted_position, Config->get_max_gain());
+
+                       } else {
+
+                               value = slider_position_to_gain_with_max (gain_adjustment.get_value(), Config->get_max_gain());
+                       }
+
+               } else {
+                       value = gain_adjustment.get_value();
+               }
+
+               if (_route && _control == _route->gain_control()) {
                        _route->set_gain (value, Controllable::UseGroup);
                } else {
                        _control->set_value (value, Controllable::NoGroup);
@@ -548,21 +586,23 @@ GainMeterBase::fader_moved ()
 void
 GainMeterBase::effective_gain_display ()
 {
-       gain_t value = GAIN_COEFF_ZERO;
-       const gain_t master_gain = _control->get_master_gain ();
+       gain_t fader_position = 0;
 
        switch (_data_type) {
        case DataType::AUDIO:
-               value = gain_to_slider_position_with_max (_control->get_value() * master_gain, Config->get_max_gain());
+               /* the position of the fader should reflect any master gain,
+                * not just the control's own inherent value
+                */
+               fader_position = gain_to_slider_position_with_max (_control->get_value() * _control->get_master_gain(), Config->get_max_gain());
                break;
        case DataType::MIDI:
-               value = _control->get_value ();
+               fader_position = _control->get_value ();
                break;
        }
 
-       if (gain_adjustment.get_value() != value) {
+       if (gain_adjustment.get_value() != fader_position) {
                ignore_toggle = true;
-               gain_adjustment.set_value (value);
+               gain_adjustment.set_value (fader_position);
                ignore_toggle = false;
        }
 }