LV2 extension to override strict-i/o per plugin

This allows mono to stereo plugins to override the default
routing and forces both outputs to be connected.

libs/ardour/ardour/lv2_extensions.h

@@ -180,6 +180,29 @@ typedef struct _LV2_License_Interface {
    @}
 */
 
+
+/**
+   @defgroup plugin port/routing control
+
+   This is a "feature" to simplify per port meta-data of
+   http://lv2plug.in/ns/ext/port-groups/port-groups.html#source
+
+   Plugins using this feature provide a strong hint that the host
+   should always connect all audio output-ports.
+
+   This allows mono->stereo plugins to override strict_io rules.
+
+   @{
+*/
+
+#define LV2_ROUTING_URI "http://harrisonconsoles.com/lv2/routing"
+#define LV2_ROUTING_PREFIX LV2_ROUTING_URI "#"
+#define LV2_ROUTING__connectAllOutputs LV2_ROUTING_PREFIX "connectAllOutputs"
+
+/**
+   @}
+*/
+
 /**
    @defgroup midnam MIDI Naming
 

libs/ardour/ardour/lv2_plugin.h

@@ -113,6 +113,7 @@ class LIBARDOUR_API LV2Plugin : public ARDOUR::Plugin, public ARDOUR::Workee
 
 	int set_block_size (pframes_t);
 	bool requires_fixed_sized_buffers () const;
+	bool connect_all_audio_outputs () const;
 
 	int connect_and_run (BufferSet& bufs,
 	                     samplepos_t start, samplepos_t end, double speed,
@@ -201,6 +202,7 @@ class LIBARDOUR_API LV2Plugin : public ARDOUR::Plugin, public ARDOUR::Workee
 	uint32_t      _patch_port_out_index;
 	URIMap&       _uri_map;
 	bool          _no_sample_accurate_ctrl;
+	bool          _connect_all_audio_outputs;
 	bool          _can_write_automation;
 	samplecnt_t   _max_latency;
 	samplecnt_t   _current_latency;

libs/ardour/ardour/plugin.h

@@ -113,8 +113,10 @@ class LIBARDOUR_API Plugin : public PBD::StatefulDestructible, public HasLatency
 	virtual void flush () { deactivate(); activate(); }
 
 	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; }
+	virtual bool connect_all_audio_outputs () const { return false; }
 
 	virtual int connect_and_run (BufferSet& bufs,
 			samplepos_t start, samplepos_t end, double speed,

libs/ardour/lv2_plugin.cc

@@ -202,6 +202,7 @@ public:
 #endif
 #ifdef LV2_EXTENDED
 	LilvNode* lv2_noSampleAccurateCtrl;
+	LilvNode* routing_connectAllOutputs; // lv2:optionalFeature
 	LilvNode* auto_can_write_automatation; // lv2:optionalFeature
 	LilvNode* auto_automation_control; // atom:supports
 	LilvNode* auto_automation_controlled; // lv2:portProperty
@@ -369,6 +370,7 @@ LV2Plugin::LV2Plugin (AudioEngine& engine,
 	, _patch_port_out_index((uint32_t)-1)
 	, _uri_map(URIMap::instance())
 	, _no_sample_accurate_ctrl (false)
+	, _connect_all_audio_outputs (false)
 {
 	init(c_plugin, rate);
 	latency_compute_run();
@@ -387,6 +389,7 @@ LV2Plugin::LV2Plugin (const LV2Plugin& other)
 	, _patch_port_out_index((uint32_t)-1)
 	, _uri_map(URIMap::instance())
 	, _no_sample_accurate_ctrl (false)
+	, _connect_all_audio_outputs (false)
 {
 	init(other._impl->plugin, other._sample_rate);
 
@@ -628,6 +631,9 @@ LV2Plugin::init(const void* c_plugin, samplecnt_t rate)
 		/* deprecated 2016-Sep-18 in favor of bufz_coarseBlockLength */
 		_no_sample_accurate_ctrl = true;
 	}
+	if (lilv_nodes_contains (optional_features, _world.routing_connectAllOutputs)) {
+		_connect_all_audio_outputs = true;
+	}
 	if (lilv_nodes_contains (optional_features, _world.auto_can_write_automatation)) {
 		_can_write_automation = true;
 	}
@@ -908,6 +914,12 @@ LV2Plugin::requires_fixed_sized_buffers () const
 	return _no_sample_accurate_ctrl;
 }
 
+bool
+LV2Plugin::connect_all_audio_outputs () const
+{
+	return _connect_all_audio_outputs;
+}
+
 LV2Plugin::~LV2Plugin ()
 {
 	DEBUG_TRACE(DEBUG::LV2, string_compose("%1 destroy\n", name()));
@@ -3252,6 +3264,7 @@ LV2World::LV2World()
 	opts_requiredOptions = lilv_new_uri(world, LV2_OPTIONS__requiredOption);
 #ifdef LV2_EXTENDED
 	lv2_noSampleAccurateCtrl    = lilv_new_uri(world, "http://ardour.org/lv2/ext#noSampleAccurateControls"); // deprecated 2016-09-18
+	routing_connectAllOutputs   = lilv_new_uri(world, LV2_ROUTING__connectAllOutputs);
 	auto_can_write_automatation = lilv_new_uri(world, LV2_AUTOMATE_URI__can_write);
 	auto_automation_control     = lilv_new_uri(world, LV2_AUTOMATE_URI__control);
 	auto_automation_controlled  = lilv_new_uri(world, LV2_AUTOMATE_URI__controlled);
@@ -3275,6 +3288,7 @@ LV2World::~LV2World()
 	lilv_node_free(bufz_powerOf2BlockLength);
 #ifdef LV2_EXTENDED
 	lilv_node_free(lv2_noSampleAccurateCtrl);
+	lilv_node_free(routing_connectAllOutputs);
 	lilv_node_free(auto_can_write_automatation);
 	lilv_node_free(auto_automation_control);
 	lilv_node_free(auto_automation_controlled);

libs/ardour/plugin_insert.cc

@@ -112,8 +112,14 @@ PluginInsert::~PluginInsert ()
 void
 PluginInsert::set_strict_io (bool b)
 {
+	if (_plugins.front()->connect_all_audio_outputs ()) {
+		/* Ignore route setting, allow plugin to add/remove ports */
+		b = false;
+	}
+
 	bool changed = _strict_io != b;
 	_strict_io = b;
+
 	if (changed) {
 		PluginConfigChanged (); /* EMIT SIGNAL */
 	}