tweak mixer VCA button appearance and prepare for live updates to VCA state

gtk2_ardour/mixer_strip.cc

@@ -83,8 +83,6 @@ using namespace ArdourMeter;
 MixerStrip* MixerStrip::_entered_mixer_strip;
 PBD::Signal1<void,MixerStrip*> MixerStrip::CatchDeletion;
 
-static const uint32_t n_vca_buttons = 4;
-
 MixerStrip::MixerStrip (Mixer_UI& mx, Session* sess, bool in_mixer)
 	: AxisView(sess)
 	, RouteUI (sess)
@@ -649,6 +647,7 @@ MixerStrip::set_route (boost::shared_ptr<Route> rt)
 
 	update_mute_display ();
 	update_solo_display ();
+	update_vca_display ();
 	name_changed ();
 	comment_changed ();
 	route_group_changed ();

gtk2_ardour/route_ui.cc

@@ -27,13 +27,16 @@
 #include <gtkmm2ext/gtk_ui.h>
 #include <gtkmm2ext/utils.h>
 
-#include "ardour/route_group.h"
-#include "ardour/dB.h"
 #include "pbd/memento_command.h"
 #include "pbd/stacktrace.h"
 #include "pbd/controllable.h"
 #include "pbd/enumwriter.h"
 
+#include "ardour/dB.h"
+#include "ardour/route_group.h"
+#include "ardour/vca.h"
+#include "ardour/vca_manager.h"
+
 #include "ardour_ui.h"
 #include "editor.h"
 #include "route_ui.h"
@@ -1273,6 +1276,35 @@ RouteUI::update_mute_display ()
         mute_button->set_active_state (mute_active_state (_session, _route));
 }
 
+void
+RouteUI::update_vca_display ()
+{
+	if (!vca_button) {
+		return;
+	}
+
+	VCAList vcas (_session->vca_manager().vcas());
+	string label;
+
+	for (VCAList::iterator v = vcas.begin(); v != vcas.end(); ++v) {
+		if (_route->slaved_to (*v)) {
+			if (!label.empty()) {
+				label += ' ';
+			}
+			label += PBD::to_string ((*v)->number(), std::dec);
+		}
+	}
+
+	if (label.empty()) {
+		label = _("-vca-");
+		vca_button->set_active_state (Gtkmm2ext::Off);
+	} else {
+		vca_button->set_active_state (Gtkmm2ext::ExplicitActive);
+	}
+
+	vca_button->set_text (label);
+}
+
 void
 RouteUI::route_rec_enable_changed ()
 {

gtk2_ardour/route_ui.h

@@ -242,6 +242,8 @@ class RouteUI : public virtual AxisView
 
 	void update_solo_display ();
 
+	void update_vca_display ();
+
 	virtual void map_frozen ();
 
 	void adjust_latency ();