Generic-MIDI ctrl: tweak pitch-bend message behavior

Add support for smoothing, ignore message when controllers are
not in sync to avoid discontinuous jumps.

This is mainly useful for Mackie-like devices that use pitch-bend
messages for faders.

see also https://discourse.ardour.org/t/feature-lazy-sliders/100961

diff --git a/libs/surfaces/generic_midi/midicontrollable.cc b/libs/surfaces/generic_midi/midicontrollable.cc
index b06a39d7a206985c1fd720f0a902663ab01d1aef..a7ea3dc36ba5bcaae1109417430144dd24811067 100644 (file)
--- a/libs/surfaces/generic_midi/midicontrollable.cc
+++ b/libs/surfaces/generic_midi/midicontrollable.cc
@@ -472,8 +472,25 @@ MIDIControllable::midi_sense_pitchbend (Parser &, pitchbend_t pb)
        _surface->maybe_start_touch (_controllable);
 
        if (!_controllable->is_toggle()) {
-               _controllable->set_value (midi_to_control (pb), Controllable::UseGroup);
+
+               float new_value = pb;
+               float max_value = max (last_controllable_value, new_value);
+               float min_value = min (last_controllable_value, new_value);
+               float range = max_value - min_value;
+               float threshold = 128.f * _surface->threshold ();
+
+               bool const in_sync = (
+                               range < threshold &&
+                               _controllable->get_value() <= midi_to_control (max_value) &&
+                               _controllable->get_value() >= midi_to_control (min_value)
+                               );
+
+               if (in_sync || _surface->motorised ()) {
+                       _controllable->set_value (midi_to_control (pb), Controllable::UseGroup);
+               }
+
                DEBUG_TRACE (DEBUG::GenericMidi, string_compose ("MIDI pitchbend %1 value %2  %3\n", (int) control_channel, (float) midi_to_control (pb), current_uri() ));
+               last_controllable_value = new_value;
        } else {
                if (pb > 8065.0f) {
                        _controllable->set_value (1, Controllable::UseGroup);