allow LV2 plugins to query current block-size.

This is akin to VST2's audioMasterGetBlockSize.
It returns the current nominal block size (think jack-buffersize).

It's not the only block size that may be used when calling run(), it's
just the normal one. The actual block sizes used may be larger or smaller
and may vary between successive calls of run().

This change became neccesary after 53e969e9. Some plugins expected 
maxBlockLength to be the /current/ buffer-size and not all-time maxiumum.
Those plugins can now use nominalBlockLength.

2 files changed, 46 insertions, 11 deletions

diff --git a/libs/ardour/ardour/lv2_plugin.h b/libs/ardour/ardour/lv2_plugin.h
index 0a83ffe63a..12e079f29c 100644
--- a/libs/ardour/ardour/lv2_plugin.h
+++ b/libs/ardour/ardour/lv2_plugin.h
@@ -96,7 +96,7 @@ class LIBARDOUR_API LV2Plugin : public ARDOUR::Plugin, public ARDOUR::Workee
 	void deactivate ();
 	void cleanup ();
 
-	int set_block_size (pframes_t /*nframes*/) { return 0; }
+	int set_block_size (pframes_t);
 
 	int connect_and_run (BufferSet& bufs,
 	                     ChanMapping in, ChanMapping out,
diff --git a/libs/ardour/lv2_plugin.cc b/libs/ardour/lv2_plugin.cc
index 62a22bb4dc..13241f2a8b 100644
--- a/libs/ardour/lv2_plugin.cc
+++ b/libs/ardour/lv2_plugin.cc
@@ -158,6 +158,7 @@ public:
 #ifdef HAVE_LV2_1_2_0
 	LilvNode* bufz_powerOf2BlockLength;
 	LilvNode* bufz_fixedBlockLength;
+	LilvNode* bufz_nominalBlockLength;
 #endif
 
 private:
@@ -238,7 +239,9 @@ log_printf(LV2_Log_Handle handle,
 struct LV2Plugin::Impl {
 	Impl() : plugin(0), ui(0), ui_type(0), name(0), author(0), instance(0)
 	       , work_iface(0)
+	       , opts_iface(0)
 	       , state(0)
+	       , block_length(0)
 	{}
 
 	/** Find the LV2 input port with the given designation.
@@ -246,16 +249,18 @@ struct LV2Plugin::Impl {
 	 */
 	const LilvPort* designated_input (const char* uri, void** bufptrs[], void** bufptr);
 
-	const LilvPlugin*           plugin;
-	const LilvUI*               ui;
-	const LilvNode*             ui_type;
-	LilvNode*                   name;
-	LilvNode*                   author;
-	LilvInstance*               instance;
-	const LV2_Worker_Interface* work_iface;
-	LilvState*                  state;
-	LV2_Atom_Forge              forge;
-	LV2_Atom_Forge              ui_forge;
+	const LilvPlugin*            plugin;
+	const LilvUI*                ui;
+	const LilvNode*              ui_type;
+	LilvNode*                    name;
+	LilvNode*                    author;
+	LilvInstance*                instance;
+	const LV2_Worker_Interface*  work_iface;
+	const LV2_Options_Interface* opts_iface;
+	LilvState*                   state;
+	LV2_Atom_Forge               forge;
+	LV2_Atom_Forge               ui_forge;
+	int32_t                      block_length;
 };
 
 LV2Plugin::LV2Plugin (AudioEngine& engine,
@@ -317,6 +322,7 @@ LV2Plugin::init(const void* c_plugin, framecnt_t rate)
 	_state_version          = 0;
 	_was_activated          = false;
 	_has_state_interface    = false;
+	_impl->block_length     = _session.get_block_size();
 
 	_instance_access_feature.URI = "http://lv2plug.in/ns/ext/instance-access";
 	_data_access_feature.URI     = "http://lv2plug.in/ns/ext/data-access";
@@ -374,6 +380,8 @@ LV2Plugin::init(const void* c_plugin, framecnt_t rate)
 		  sizeof(int32_t), atom_Int, &_max_block_length },
 		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id(LV2_BUF_SIZE__sequenceSize),
 		  sizeof(int32_t), atom_Int, &_seq_size },
+		{ LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id("http://lv2plug.in/ns/ext/buf-size#nominalBlockLength"),
+		  sizeof(int32_t), atom_Int, &_impl->block_length },
 		{ LV2_OPTIONS_INSTANCE, 0, 0, 0, 0, NULL }
 	};
 
@@ -427,6 +435,14 @@ LV2Plugin::init(const void* c_plugin, framecnt_t rate)
 	}
 	lilv_node_free(worker_iface_uri);
 
+
+	LilvNode* options_iface_uri = lilv_new_uri(_world.world, LV2_OPTIONS__interface);
+	if (lilv_plugin_has_extension_data(plugin, options_iface_uri)) {
+		_impl->opts_iface = (const LV2_Options_Interface*)extension_data(
+			LV2_OPTIONS__interface);
+	}
+	lilv_node_free(options_iface_uri);
+
 	if (lilv_plugin_has_feature(plugin, _world.lv2_inPlaceBroken)) {
 		error << string_compose(
 		    _("LV2: \"%1\" cannot be used, since it cannot do inplace processing."),
@@ -636,6 +652,23 @@ LV2Plugin::init(const void* c_plugin, framecnt_t rate)
 	latency_compute_run();
 }
 
+int
+LV2Plugin::set_block_size (pframes_t nframes)
+{
+#ifdef HAVE_LV2_1_2_0
+	if (_impl->opts_iface) {
+		LV2_URID atom_Int = _uri_map.uri_to_id(LV2_ATOM__Int);
+		_impl->block_length = nframes;
+		LV2_Options_Option block_size_option = {
+			LV2_OPTIONS_INSTANCE, 0, _uri_map.uri_to_id ("http://lv2plug.in/ns/ext/buf-size#nominalBlockLength"),
+			sizeof(int32_t), atom_Int, (void*)&_impl->block_length
+		};
+		_impl->opts_iface->set (_impl->instance->lv2_handle, &block_size_option);
+	}
+#endif
+	return 0;
+}
+
 LV2Plugin::~LV2Plugin ()
 {
 	DEBUG_TRACE(DEBUG::LV2, string_compose("%1 destroy\n", name()));
@@ -2395,6 +2428,7 @@ LV2World::LV2World()
 #ifdef HAVE_LV2_1_2_0
 	bufz_powerOf2BlockLength = lilv_new_uri(world, LV2_BUF_SIZE__powerOf2BlockLength);
 	bufz_fixedBlockLength    = lilv_new_uri(world, LV2_BUF_SIZE__fixedBlockLength);
+	bufz_nominalBlockLength  = lilv_new_uri(world, "http://lv2plug.in/ns/ext/buf-size#nominalBlockLength");
 #endif
 
 }
@@ -2402,6 +2436,7 @@ LV2World::LV2World()
 LV2World::~LV2World()
 {
 #ifdef HAVE_LV2_1_2_0
+	lilv_node_free(bufz_nominalBlockLength);
 	lilv_node_free(bufz_fixedBlockLength);
 	lilv_node_free(bufz_powerOf2BlockLength);
 #endif