do not update LV2 output port displays unless the value has changed

diff --git a/gtk2_ardour/lv2_plugin_ui.cc b/gtk2_ardour/lv2_plugin_ui.cc
index 153f4efdd93bf37c34c60708502dc23d0d7b356b..9634a05d0a6da72d41fc3a03bdb786e29f4051ad 100644 (file)
--- a/gtk2_ardour/lv2_plugin_ui.cc
+++ b/gtk2_ardour/lv2_plugin_ui.cc
@@ -189,8 +189,14 @@ LV2PluginUI::output_update()
        uint32_t nports = _output_ports.size();
        for (uint32_t i = 0; i < nports; ++i) {
                uint32_t index = _output_ports[i];
-               float val = _lv2->get_parameter(index);
-               suil_instance_port_event ((SuilInstance*)_inst, index, 4, 0, &val);
+               float val = _lv2->get_parameter (index);
+
+               if (val != _values[index]) {
+                       /* Send to GUI */
+                       suil_instance_port_event ((SuilInstance*)_inst, index, 4, 0, &val);
+                       /* Cache current value */
+                       _values[index] = val;
+               }
        }
 
        /* Input ports marked for update because the control value changed
@@ -368,10 +374,16 @@ LV2PluginUI::lv2ui_instantiate(const std::string& title)
 
        _values = new float[num_ports];
        _controllables.resize(num_ports);
+
        for (uint32_t i = 0; i < num_ports; ++i) {
                bool     ok;
                uint32_t port = _lv2->nth_parameter(i, ok);
                if (ok) {
+                       /* Cache initial value of the parameter, regardless of
+                          whether it is input or output
+                       */
+
+                       _values[port]        = _lv2->get_parameter(port);
                        _controllables[port] = boost::dynamic_pointer_cast<ARDOUR::AutomationControl> (
                                insert->control(Evoral::Parameter(PluginAutomation, 0, port)));
 
@@ -379,9 +391,10 @@ LV2PluginUI::lv2ui_instantiate(const std::string& title)
                                if (_controllables[port]) {
                                        _controllables[port]->Changed.connect (control_connections, invalidator (*this), boost::bind (&LV2PluginUI::control_changed, this, port), gui_context());
                                }
-                               /* queue for first update ("push") to GUI */
-                               _updates.insert (port);
                        }
+
+                       /* queue for first update ("push") to GUI */
+                       _updates.insert (port);
                }
        }