provider: Add API to query supported protocols

These are the protocols that the provider plugin may support. The origins
must be queried independently whether or not they support any given protocol.

Example: A SIP origin/account may or may not support the "tel" protocol.

src/calls-provider.c

@@ -72,6 +72,12 @@ calls_provider_real_get_origins (CallsProvider *self)
   return NULL;
 }
 
+static const char * const *
+calls_provider_real_get_protocols (CallsProvider *self)
+{
+  g_assert_not_reached ();
+}
+
 
 static void
 calls_provider_get_property (GObject    *object,
@@ -101,6 +107,7 @@ calls_provider_class_init (CallsProviderClass *klass)
   klass->get_name = calls_provider_real_get_name;
   klass->get_status = calls_provider_real_get_status;
   klass->get_origins = calls_provider_real_get_origins;
+  klass->get_protocols = calls_provider_real_get_protocols;
 
   props[PROP_STATUS] =
     g_param_spec_string ("status",
@@ -223,3 +230,17 @@ calls_provider_unload_plugin (const char *name)
   else
     g_warning ("Can't unload plugin: No plugin with name %s found", name);
 }
+
+/**
+ * calls_provider_get_protocols:
+ * @self: A #CallsProvider
+ *
+ * Returns: (transfer none): A null-terminated array of strings
+ */
+const char * const *
+calls_provider_get_protocols (CallsProvider *self)
+{
+  g_return_val_if_fail (CALLS_IS_PROVIDER (self), NULL);
+
+  return CALLS_PROVIDER_GET_CLASS (self)->get_protocols (self);
+}

src/calls-provider.h

@@ -47,6 +47,7 @@ struct _CallsProviderClass
   const char         *(*get_name)                       (CallsProvider *self);
   const char         *(*get_status)                     (CallsProvider *self);
   GListModel         *(*get_origins)                    (CallsProvider *self);
+  const char * const *(*get_protocols)                  (CallsProvider *self);
 };
 
 const char           *calls_provider_get_name           (CallsProvider *self);
@@ -54,6 +55,7 @@ const char           *calls_provider_get_status         (CallsProvider *self);
 GListModel           *calls_provider_get_origins        (CallsProvider *self);
 CallsProvider        *calls_provider_load_plugin        (const char    *name);
 void                  calls_provider_unload_plugin      (const char    *name);
+const char * const   *calls_provider_get_protocols       (CallsProvider *self);
 
 
 G_END_DECLS