add Plugin LatencyChanged() signal and max latency report

3 files changed, 41 insertions, 0 deletions

diff --git a/libs/ardour/ardour/lv2_plugin.h b/libs/ardour/ardour/lv2_plugin.h
index c93c159a78..f1907e80ae 100644
--- a/libs/ardour/ardour/lv2_plugin.h
+++ b/libs/ardour/ardour/lv2_plugin.h
@@ -71,6 +71,7 @@ class LIBARDOUR_API LV2Plugin : public ARDOUR::Plugin, public ARDOUR::Workee
 	uint32_t    num_ports () const;
 	uint32_t    parameter_count () const;
 	float       default_value (uint32_t port);
+	framecnt_t  max_latency () const;
 	framecnt_t  signal_latency () const;
 	void        set_parameter (uint32_t port, float val);
 	float       get_parameter (uint32_t port) const;
@@ -190,6 +191,8 @@ class LIBARDOUR_API LV2Plugin : public ARDOUR::Plugin, public ARDOUR::Workee
 	URIMap&       _uri_map;
 	bool          _no_sample_accurate_ctrl;
 	bool          _can_write_automation;
+	framecnt_t    _max_latency;
+	framecnt_t    _current_latency;
 
 	friend const void* lv2plugin_get_port_value(const char* port_symbol,
 	                                            void*       user_data,
diff --git a/libs/ardour/ardour/plugin.h b/libs/ardour/ardour/plugin.h
index e219ec5bdd..087f5968bd 100644
--- a/libs/ardour/ardour/plugin.h
+++ b/libs/ardour/ardour/plugin.h
@@ -199,6 +199,26 @@ class LIBARDOUR_API Plugin : public PBD::StatefulDestructible, public Latent
 		return 0;
 	}
 
+	/** Emitted when a Latency Changes
+	 *
+	 * (this cannot be part of ARDOUR::Latent because
+	 * signals cannot be copy-constructed).
+	 */
+	PBD::Signal2<void,framecnt_t, framecnt_t> LatencyChanged;
+
+	/* overload Latent::set_user_latency w/signal emission */
+	virtual void set_user_latency (framecnt_t val) {
+		bool changed = val != _user_latency;
+		framecnt_t old = effective_latency ();
+		_user_latency = val;
+		if (changed) {
+			LatencyChanged (old, effective_latency ()); /* EMIT SIGNAL */
+		}
+	}
+
+	/** the max possible latency a plugin will have */
+	virtual framecnt_t max_latency () const { return 0; } // TODO = 0, require implementation
+
 	/** Emitted when a preset is added or removed, respectively */
 	PBD::Signal0<void> PresetAdded;
 	PBD::Signal0<void> PresetRemoved;
diff --git a/libs/ardour/lv2_plugin.cc b/libs/ardour/lv2_plugin.cc
index 46582a5fcf..e13328b97b 100644
--- a/libs/ardour/lv2_plugin.cc
+++ b/libs/ardour/lv2_plugin.cc
@@ -365,6 +365,8 @@ LV2Plugin::init(const void* c_plugin, framecnt_t rate)
 	_was_activated          = false;
 	_has_state_interface    = false;
 	_can_write_automation   = false;
+	_max_latency            = 0;
+	_current_latency        = 0;
 	_impl->block_length     = _session.get_block_size();
 
 	_instance_access_feature.URI = "http://lv2plug.in/ns/ext/instance-access";
@@ -673,6 +675,9 @@ LV2Plugin::init(const void* c_plugin, framecnt_t rate)
 			lilv_instance_connect_port(_impl->instance, i, &_control_data[i]);
 
 			if (latent && i == latency_index) {
+				LilvNode *max;
+				lilv_port_get_range(_impl->plugin, port, NULL, NULL, &max);
+				_max_latency = max ? lilv_node_as_float(max) : .02 * _sample_rate;
 				_latency_control_port  = &_control_data[i];
 				*_latency_control_port = 0;
 			}
@@ -2009,6 +2014,12 @@ LV2Plugin::describe_parameter(Evoral::Parameter which)
 }
 
 framecnt_t
+LV2Plugin::max_latency () const
+{
+	return _max_latency;
+}
+
+framecnt_t
 LV2Plugin::signal_latency() const
 {
 	if (_latency_control_port) {
@@ -2546,6 +2557,13 @@ LV2Plugin::connect_and_run(BufferSet& bufs,
 	_next_cycle_speed = _session.transport_speed();
 	_next_cycle_start = _session.transport_frame() + (nframes * _next_cycle_speed);
 
+	if (_latency_control_port) {
+		framecnt_t new_latency = signal_latency ();
+		if (_current_latency != new_latency) {
+			LatencyChanged (_current_latency, new_latency); /* EMIT SIGNAL */
+		}
+		_current_latency = new_latency;
+	}
 	return 0;
 }