Add proper API to expose plugin tailtime

This is in preparation to display current tail time,
and allow a user to override it.

This is similar to existing processor latency API.

libs/ardour/ardour/plugin.h

@@ -40,6 +40,7 @@
 #include "ardour/midi_ring_buffer.h"
 #include "ardour/midi_state_tracker.h"
 #include "ardour/parameter_descriptor.h"
+#include "ardour/tailtime.h"
 #include "ardour/types.h"
 #include "ardour/variant.h"
 
@@ -74,7 +75,7 @@ typedef std::set<uint32_t>            PluginOutputConfiguration;
  *
  * Plugins are not used directly in Ardour but always wrapped by a PluginInsert.
  */
-class LIBARDOUR_API Plugin : public PBD::StatefulDestructible, public HasLatency
+class LIBARDOUR_API Plugin : public PBD::StatefulDestructible, public HasLatency, public HasTailTime
 {
 public:
 	Plugin (ARDOUR::AudioEngine&, ARDOUR::Session&);
@@ -172,12 +173,14 @@ public:
 		return plugin_latency ();
 	}
 
+	samplecnt_t signal_tailtime () const
+	{
+		return plugin_tailtime ();
+	}
+
 	/** the max possible latency a plugin will have */
 	virtual samplecnt_t max_latency () const { return 0; }
 
-	samplecnt_t effective_tail() const;
-	PBD::Signal0<void> TailChanged;
-
 	virtual int  set_block_size (pframes_t nframes) = 0;
 	virtual bool requires_fixed_sized_buffers () const { return false; }
 	virtual bool inplace_broken () const { return false; }
@@ -429,7 +432,7 @@ private:
 	/** tail duration in samples. e.g. for reverb or delay plugins.
 	 *
 	 * The default when unknown is 2 sec */
-	virtual samplecnt_t plugin_tail () const;
+	virtual samplecnt_t plugin_tailtime () const;
 
 
 	/** Fill _presets with our presets */

libs/ardour/ardour/region_fx_plugin.h

@@ -43,7 +43,7 @@ namespace ARDOUR
 {
 class ReadOnlyControl;
 
-class LIBARDOUR_API RegionFxPlugin : public SessionObject, public PlugInsertBase, public Latent, public Temporal::TimeDomainProvider
+class LIBARDOUR_API RegionFxPlugin : public SessionObject, public PlugInsertBase, public Latent, public TailTime, public Temporal::TimeDomainProvider
 {
 public:
 	RegionFxPlugin (Session&, Temporal::TimeDomain const, std::shared_ptr<Plugin> = std::shared_ptr<Plugin> ());
@@ -61,6 +61,8 @@ public:
 
 	/* Latent */
 	samplecnt_t signal_latency () const;
+	/* TailTime */
+	samplecnt_t signal_tailtime () const;
 
 	/* PlugInsertBase */
 	uint32_t get_count () const
@@ -153,10 +155,6 @@ public:
 		return _required_buffers;
 	}
 
-	/* wrapped Plugin API */
-	PBD::Signal0<void> TailChanged;
-	samplecnt_t effective_tail () const;
-
 private:
 	/* disallow copy construction */
 	RegionFxPlugin (RegionFxPlugin const&);
@@ -178,7 +176,8 @@ private:
 	/** details of the match currently being used */
 	Match _match;
 
-	uint32_t _plugin_signal_latency;
+	samplecnt_t _plugin_signal_latency;
+	samplecnt_t _plugin_signal_tailtime;
 
 	typedef std::vector<std::shared_ptr<Plugin>> Plugins;
 	Plugins                                      _plugins;

libs/ardour/ardour/tailtime.h

@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2024 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef __ardour_tailtime_h__
+#define __ardour_tailtime_h__
+
+#include "pbd/signals.h"
+
+#include "ardour/libardour_visibility.h"
+#include "ardour/types.h"
+
+namespace ARDOUR {
+
+class LIBARDOUR_API HasTailTime {
+public:
+	virtual ~HasTailTime () {}
+	virtual samplecnt_t signal_tailtime () const = 0;
+};
+
+class LIBARDOUR_API TailTime : public HasTailTime {
+public:
+	TailTime ();
+	TailTime (TailTime const&);
+	virtual ~TailTime() {}
+
+	samplecnt_t effective_tailtime () const;
+
+	samplecnt_t user_latency () const {
+		if (_use_user_tailtime) {
+			return _user_tailtime;
+		} else {
+			return 0;
+		}
+	}
+
+	void unset_user_tailtime ();
+	void set_user_tailtime (samplecnt_t val);
+
+	PBD::Signal0<void> TailTimeChanged;
+
+protected:
+	int  set_state (const XMLNode& node, int version);
+	void add_state (XMLNode*) const;
+
+private:
+	samplecnt_t _use_user_tailtime;
+	samplecnt_t _user_tailtime;
+};
+
+} /* namespace */
+
+
+#endif /* __ardour_tailtime_h__*/
+

libs/ardour/ardour/vst3_plugin.h

@@ -182,7 +182,7 @@ public:
 
 	/* API for Ardour -- Setup/Processing */
 	uint32_t plugin_latency ();
-	uint32_t plugin_tail ();
+	uint32_t plugin_tailtime ();
 	bool     set_block_size (int32_t);
 	bool     activate ();
 	bool     deactivate ();
@@ -444,7 +444,7 @@ public:
 
 private:
 	samplecnt_t plugin_latency () const;
-	samplecnt_t plugin_tail () const;
+	samplecnt_t plugin_tailtime () const;
 	void        init ();
 	void        find_presets ();
 	void        forward_resize_view (int w, int h);

libs/ardour/audioregion.cc

@@ -2488,7 +2488,7 @@ AudioRegion::_add_plugin (std::shared_ptr<RegionFxPlugin> rfx, std::shared_ptr<R
 	}
 
 	rfx->LatencyChanged.connect_same_thread (*this, boost::bind (&AudioRegion::fx_latency_changed, this, false));
-	rfx->TailChanged.connect_same_thread (*this, boost::bind (&AudioRegion::fx_tail_changed, this, false));
+	rfx->TailTimeChanged.connect_same_thread (*this, boost::bind (&AudioRegion::fx_tail_changed, this, false));
 	rfx->set_block_size (_session.get_block_size ());
 
 	if (from_set_state) {
@@ -2576,7 +2576,7 @@ AudioRegion::fx_tail_changed (bool no_emit)
 {
 	uint32_t t = 0;
 	for (auto const& rfx : _plugins) {
-		t = max<uint32_t> (t, rfx->effective_tail ());
+		t = max<uint32_t> (t, rfx->effective_tailtime ());
 	}
 	if (t == _fx_tail) {
 		return;

libs/ardour/plugin.cc

@@ -318,14 +318,7 @@ Plugin::input_streams () const
 }
 
 samplecnt_t
-Plugin::effective_tail () const
-{
-	/* consider adding a user-override per plugin; compare to HasLatency, Latent */
-	return max<samplecnt_t> (0, min<samplecnt_t> (plugin_tail (), Config->get_max_tail_samples ()));
-}
-
-samplecnt_t
-Plugin::plugin_tail () const
+Plugin::plugin_tailtime () const
 {
 	return _session.sample_rate () * Config->get_tail_duration_sec ();
 }

libs/ardour/region.cc

@@ -2475,7 +2475,7 @@ Region::fx_tail_changed (bool)
 {
 	uint32_t t = 0;
 	for (auto const& rfx : _plugins) {
-		t = max<uint32_t> (t, rfx->plugin()->effective_tail ());
+		t = max<uint32_t> (t, rfx->effective_tailtime ());
 	}
 	if (t == _fx_tail) {
 		return;

libs/ardour/region_fx_plugin.cc

@@ -250,6 +250,7 @@ RegionFxPlugin::get_state () const
 	XMLNode* node = new XMLNode (/*state_node_name*/ "RegionFXPlugin");
 
 	Latent::add_state (node);
+	TailTime::add_state (node);
 
 	node->set_property ("type", _plugins[0]->state_node_name ());
 	node->set_property ("unique-id", _plugins[0]->unique_id ());
@@ -383,6 +384,10 @@ RegionFxPlugin::set_state (const XMLNode& node, int version)
 			ac->Changed (false, Controllable::NoGroup); /* EMIT SIGNAL */
 		}
 	}
+
+	Latent::set_state (node, version);
+	TailTime::set_state (node, version);
+
 	return 0;
 }
 
@@ -422,7 +427,6 @@ RegionFxPlugin::add_plugin (std::shared_ptr<Plugin> plugin)
 		plugin->ParameterChangedExternally.connect_same_thread (*this, boost::bind (&RegionFxPlugin::parameter_changed_externally, this, _1, _2));
 		plugin->StartTouch.connect_same_thread (*this, boost::bind (&RegionFxPlugin::start_touch, this, _1));
 		plugin->EndTouch.connect_same_thread (*this, boost::bind (&RegionFxPlugin::end_touch, this, _1));
-		plugin->TailChanged.connect_same_thread (*this, [this](){ TailChanged (); });
 	}
 
 	plugin->set_insert (this, _plugins.size ());
@@ -503,12 +507,12 @@ RegionFxPlugin::signal_latency () const
 }
 
 ARDOUR::samplecnt_t
-RegionFxPlugin::effective_tail () const
+RegionFxPlugin::signal_tailtime () const
 {
 	if (_plugins.empty ()) {
 		return 0;
 	}
-	return _plugins.front ()->effective_tail ();
+	return _plugins.front ()->signal_tailtime ();
 }
 
 PlugInsertBase::UIElements
@@ -1440,6 +1444,11 @@ RegionFxPlugin::connect_and_run (BufferSet& bufs, samplepos_t start, samplepos_t
 		_plugin_signal_latency= l;
 		LatencyChanged (); /* EMIT SIGNAL */
 	}
+	const samplecnt_t t = effective_latency ();
+	if (_plugin_signal_tailtime != l) {
+		_plugin_signal_tailtime = t;
+		TailTimeChanged (); /* EMIT SIGNAL */
+	}
 	return true;
 }
 

libs/ardour/tailtime.cc

@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2024 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "pbd/xml++.h"
+
+#include "ardour/tailtime.h"
+#include "ardour/rc_configuration.h"
+
+using namespace ARDOUR;
+
+TailTime::TailTime ()
+	: HasTailTime ()
+	, _use_user_tailtime (false)
+	, _user_tailtime (0)
+{}
+
+TailTime::TailTime (TailTime const& other)
+	: HasTailTime ()
+	, _use_user_tailtime (other._use_user_tailtime)
+	, _user_tailtime (other._user_tailtime)
+{}
+
+samplecnt_t
+TailTime::effective_tailtime () const
+{
+	if (_use_user_tailtime) {
+		return _user_tailtime;
+	} else {
+		return std::max<samplecnt_t> (0, std::min<samplecnt_t> (signal_tailtime (), Config->get_max_tail_samples ()));
+	}
+}
+
+void
+TailTime::set_user_tailtime (samplecnt_t val)
+{
+	if (_use_user_tailtime && _user_tailtime == val) {
+		return;
+	}
+	_use_user_tailtime = true;
+	_user_tailtime = val;
+	TailTimeChanged (); /* EMIT SIGNAL */
+}
+
+void
+TailTime::unset_user_tailtime ()
+{
+	if (!_use_user_tailtime) {
+		return;
+	}
+	_use_user_tailtime = false;
+	_user_tailtime = 0;
+	TailTimeChanged (); /* EMIT SIGNAL */
+}
+
+
+
+int
+TailTime::set_state (const XMLNode& node, int version)
+{
+	node.get_property ("user-tailtime", _user_tailtime);
+	if (!node.get_property ("use-user-tailtime", _use_user_tailtime)) {
+		_use_user_tailtime = _user_tailtime > 0;
+	}
+	return 0;
+}
+
+void
+TailTime::add_state (XMLNode* node) const
+{
+	node->set_property ("user-tailtime", _user_tailtime);
+	node->set_property ("use-user-tailtime", _use_user_tailtime);
+}

libs/ardour/vst3_plugin.cc

@@ -678,9 +678,9 @@ VST3Plugin::set_block_size (pframes_t n_samples)
 }
 
 samplecnt_t
-VST3Plugin::plugin_tail () const
+VST3Plugin::plugin_tailtime () const
 {
-	return _plug->plugin_tail ();
+	return _plug->plugin_tailtime ();
 }
 
 samplecnt_t
@@ -1816,7 +1816,7 @@ VST3PI::plugin_latency ()
 }
 
 uint32_t
-VST3PI::plugin_tail ()
+VST3PI::plugin_tailtime ()
 {
 	if (!_plugin_tail) { // XXX this is currently never reset
 		_plugin_tail = _processor->getTailSamples ();

libs/ardour/wscript

@@ -256,6 +256,7 @@ libardour_sources = [
         'system_exec.cc',
         'revision.cc',
         'rt_midibuffer.cc',
+        'tailtime.cc',
         'template_utils.cc',
         'tempo_map_importer.cc',
         'thawlist.cc',