Clarified lv2.h header for HostFeatures parameter, associated changes to SLV2.

git-svn-id: http://svn.drobilla.net/lad/slv2@195 a436a847-0d15-0410-975c-d299462d15a1

4 files changed, 22 insertions, 7 deletions

diff --git a/examples/hosts/jack_host.c b/examples/hosts/jack_host.c
index a29fb13..655c939 100644
--- a/examples/hosts/jack_host.c
+++ b/examples/hosts/jack_host.c
@@ -28,7 +28,7 @@ struct JackHost {
 	jack_client_t* jack_client; /**< Jack client */
 	SLV2Plugin*    plugin;      /**< Plugin "class" (actually just a few strings) */
 	SLV2Instance*  instance;    /**< Plugin "instance" (loaded shared lib) */
-	size_t         num_ports;   /**< Size of the two following arrays: */
+	uint32_t       num_ports;   /**< Size of the two following arrays: */
 	jack_port_t**  jack_ports;  /**< For audio ports, otherwise NULL */
 	float*         controls;    /**< For control ports, otherwise 0.0f */
 };
@@ -97,10 +97,10 @@ main(int argc, char** argv)
 	
 	/* Create ports */
 	host.num_ports  = slv2_plugin_get_num_ports(host.plugin);
-	host.jack_ports = calloc(host.num_ports, sizeof(jack_port_t*));
-	host.controls   = calloc(host.num_ports, sizeof(float*));
+	host.jack_ports = calloc((size_t)host.num_ports, sizeof(jack_port_t*));
+	host.controls   = calloc((size_t)host.num_ports, sizeof(float*));
 	
-	for (size_t i=0; i < host.num_ports; ++i)
+	for (uint32_t i=0; i < host.num_ports; ++i)
 		create_port(&host, i);
 	
 	/* Activate plugin and JACK */
@@ -198,7 +198,7 @@ jack_process_cb(jack_nframes_t nframes, void* data)
 	struct JackHost* host = (struct JackHost*)data;
 
 	/* Connect plugin ports directly to JACK buffers */
-	for (size_t i=0; i < host->num_ports; ++i)
+	for (uint32_t i=0; i < host->num_ports; ++i)
 		if (host->jack_ports[i] != NULL)
 			slv2_instance_connect_port(host->instance, i,
 				jack_port_get_buffer(host->jack_ports[i], nframes));
diff --git a/slv2/lv2.h b/slv2/lv2.h
index b3d97bf..7e3b14e 100644
--- a/slv2/lv2.h
+++ b/slv2/lv2.h
@@ -146,13 +146,15 @@ typedef struct _LV2_Descriptor {
    * found. This function must return NULL if instantiation fails.
    *
    * BundlePath is a string of the path to the plugin's .lv2 bundle
-   * directory, it MUST not include the trailing /.
+   * directory, it MUST NOT include the trailing /.
    *
    * HostFeatures is a NULL terminated array of the URIs of the LV2
    * features that the host supports. Plugins may refuse to instantiate
    * if required features are not found here (however hosts SHOULD NOT use
    * this as a discovery mechanism, instead reading the data file before
-   * attempting to instantiate the plugin).
+   * attempting to instantiate the plugin).  This array must always exist;
+   * if a host has no features, it MUST pass a single element array
+   * containing NULL (to simplify plugins).
    *
    * Note that instance initialisation should generally occur in
    * activate() rather than here.  If a host calls instantiate, it MUST
diff --git a/slv2/plugininstance.h b/slv2/plugininstance.h
index aba3f95..553bb74 100644
--- a/slv2/plugininstance.h
+++ b/slv2/plugininstance.h
@@ -54,6 +54,10 @@ typedef const struct _Instance SLV2Instance;
  * \a plugin is not modified or directly referenced by the returned object
  * (instances store only a copy of the plugin's URI).
  * 
+ * \a host_features NULL-terminated array of features the host supports.
+ * NULL may be passed if the host supports no additional features (unlike
+ * the LV2 specification - SLV2 takes care of it).
+ *
  * \return NULL if instantiation failed.
  */
 SLV2Instance*
diff --git a/src/plugininstance.c b/src/plugininstance.c
index 1566c7d..9db7d26 100644
--- a/src/plugininstance.c
+++ b/src/plugininstance.c
@@ -35,6 +35,12 @@ slv2_plugin_instantiate(const SLV2Plugin*        plugin,
 {
 	struct _Instance* result = NULL;
 	
+	bool local_host_features = (host_features == NULL);
+	if (local_host_features) {
+		host_features = malloc(sizeof(LV2_Host_Feature));
+		host_features[0] = NULL;
+	}
+	
 	const char* const lib_path = slv2_plugin_get_library_path(plugin);
 	if (!lib_path)
 		return NULL;
@@ -90,6 +96,9 @@ slv2_plugin_instantiate(const SLV2Plugin*        plugin,
 	for (uint32_t i=0; i < slv2_plugin_get_num_ports(plugin); ++i)
 		result->descriptor->connect_port(result->lv2_handle, i, NULL);
 	
+	if (local_host_features)
+		free(host_features);
+
 	return result;
 }