+void
+GainControl::inc_gain (gain_t factor)
+{
+ /* To be used ONLY when doing group-relative gain adjustment, from
+ * ControlGroup::set_group_values().
+ */
+
+ const float desired_gain = user_double();
+
+ if (fabsf (desired_gain) < GAIN_COEFF_SMALL) {
+ // really?! what's the idea here?
+ actually_set_value (0.000001f + (0.000001f * factor), Controllable::ForGroup);
+ } else {
+ actually_set_value (desired_gain + (desired_gain * factor), Controllable::ForGroup);
+ }
+}
+
+void
+GainControl::recompute_masters_ratios (double val)
+{
+ /* Master WRITE lock must be held */
+
+ /* V' is the new gain value for this
+
+ Mv(n) is the return value of ::get_value() for the n-th master
+ Mr(n) is the return value of ::ratio() for the n-th master record
+
+ the slave should return V' on the next call to ::get_value().
+
+ but the value is determined by the masters, so we know:
+
+ V' = (Mv(1) * Mr(1)) * (Mv(2) * Mr(2)) * ... * (Mv(n) * Mr(n))
+
+ hence:
+
+ Mr(1) * Mr(2) * ... * (Mr(n) = V' / (Mv(1) * Mv(2) * ... * Mv(n))
+
+ if we make all ratios equal (i.e. each master contributes the same
+ fraction of its own gain level to make the final slave gain), then we
+ have:
+
+ pow (Mr(n), n) = V' / (Mv(1) * Mv(2) * ... * Mv(n))
+
+ which gives
+
+ Mr(n) = pow ((V' / (Mv(1) * Mv(2) * ... * Mv(n))), 1/n)
+
+ Mr(n) is the new ratio number for the slaves
+ */
+
+
+ const double nmasters = _masters.size();
+ double masters_total_gain_coefficient = 1.0;
+
+ for (Masters::iterator mr = _masters.begin(); mr != _masters.end(); ++mr) {
+ masters_total_gain_coefficient *= mr->second.master()->get_value();
+ }
+
+ const double new_universal_ratio = pow ((val / masters_total_gain_coefficient), (1.0/nmasters));
+
+ for (Masters::iterator mr = _masters.begin(); mr != _masters.end(); ++mr) {
+ mr->second.reset_ratio (new_universal_ratio);
+ }
+}
+
+XMLNode&
+GainControl::get_state ()
+{
+ XMLNode& node (AutomationControl::get_state());
+
+#if 0
+ /* store VCA master IDs */
+
+ string str;
+
+ {
+ Glib::Threads::RWLock::ReaderLock lm (master_lock);
+ for (Masters::const_iterator mr = _masters.begin(); mr != _masters.end(); ++mr) {
+ if (!str.empty()) {
+ str += ',';
+ }
+ str += PBD::to_string (mr->first, std::dec);
+ }
+ }
+
+ if (!str.empty()) {
+ node.add_property (X_("masters"), str);
+ }
+#endif
+
+ return node;
+}
+
+int
+GainControl::set_state (XMLNode const& node, int version)
+{
+ return AutomationControl::set_state (node, version);
+}
+