Adding self registering keys to lua-factory

For the past few weeks I’ve been hacking away at GNOME Games and Grilo. Here’s what I’ve done so far.

May 14th - June 3rd

My first task was to fetch metadata using thegamesdb and use it to get developer and publisher of a game to GNOME Games. For this, I had to add the appropriate system keys to Grilo, the only problem being the keys in question were too app-specific to be added as system keys and there was no provision of self registering keys in lua based sources.

The struggle

The solution was pretty simple, I began implementing self registering keys to Grilo for lua sources to use all the while fixing any bugs I encountered on the way.

Bastien Nocera, gave me a very bright idea to register new keys while setting their value to GRL_DATA itself. I completed this by implementing two function in Grilo.

• grl_data_set_for_id ()
• grl_data_add_for_id ()

How do they work?

void grl_data_set_for_id (GrlData *data, const gchar *key_name, const GValue *value);

The key_name to be registered, value to be set and data object are first passed as parameter to the function.

  registry = grl_registry_get_default ();
  key_id = grl_registry_lookup_metadata_key (registry, key_name);

The key_name is then looked up in the registry for any matching GrlKeyID.

  if (key_id != GRL_METADATA_KEY_INVALID) {
    grl_data_set (data, key_id, value);
  }

If found, the data is set normally using grl_data_set ().

else {
    switch (G_VALUE_TYPE (value)) {
    case G_TYPE_INT:
      spec = g_param_spec_int (key_name,
                               key_name,
                               key_name,
                               0, G_MAXINT,
                               0,
                               G_PARAM_STATIC_STRINGS | G_PARAM_READWRITE);

      key_id = grl_registry_register_metadata_key (registry, spec, GRL_METADATA_KEY_INVALID, NULL);
      grl_data_set (data, key_id, value);
      break;

    case G_TYPE_INT64:
      spec = g_param_spec_int64 (key_name,
                                 key_name,
                                 key_name,
                                 -1, G_MAXINT64,
                                 -1,
                                 G_PARAM_STATIC_STRINGS | G_PARAM_READWRITE);

      key_id = grl_registry_register_metadata_key (registry, spec, GRL_METADATA_KEY_INVALID, NULL);
      grl_data_set (data, key_id, value);
      break;

    case G_TYPE_STRING:
      spec = g_param_spec_string (key_name,
                                  key_name,
                                  key_name,
                                  NULL,
                                  G_PARAM_STATIC_STRINGS | G_PARAM_READWRITE);

      key_id = grl_registry_register_metadata_key (registry, spec, GRL_METADATA_KEY_INVALID, NULL);
      grl_data_set (data, key_id, value);
      break;

    case G_TYPE_BOOLEAN:
      spec = g_param_spec_boolean (key_name,
                                   key_name,
                                   key_name,
                                   FALSE,
                                   G_PARAM_STATIC_STRINGS | G_PARAM_READWRITE);

      key_id = grl_registry_register_metadata_key (registry, spec, GRL_METADATA_KEY_INVALID, NULL);
      grl_data_set (data, key_id, value);
      break;

    case G_TYPE_FLOAT:
      spec = g_param_spec_float (key_name,
                                 key_name,
                                 key_name,
                                 0, G_MAXFLOAT,
                                 0,
                                 G_PARAM_STATIC_STRINGS | G_PARAM_READWRITE);

      key_id = grl_registry_register_metadata_key (registry, spec, GRL_METADATA_KEY_INVALID, NULL);
      grl_data_set (data, key_id, value);
      break;

    default:
      if (type == G_TYPE_DATE_TIME) {
        spec = g_param_spec_boxed (key_name,
                                   key_name,
                                   key_name,
                                   G_TYPE_DATE_TIME,
                                   G_PARAM_STATIC_STRINGS | G_PARAM_READWRITE);

        key_id = grl_registry_register_metadata_key (registry, spec, GRL_METADATA_KEY_INVALID, NULL);
        grl_data_set (data, key_id, value);
      }
    }
  }
}

If not found, the appropriate g_param_spec is defined for that particular G_TYPE, the key is then registered using grl_registry_regsiter_metadata_key () and value is set using grl_data_set (). This function sets the first value associated with key_name in data. If key_name already has a first value, old value is replaced by the new one.

void grl_data_set_for_id (GrlData *data, const gchar *key_name, const GValue *value);

This function also works similarly to the same as above one, with only a few minor differences. The value associated with key_name to data is appended instead of set. This key_name is used to create a new GParamSpec instance, which is further used to create and register a key using grl_registry_register_metadata_key(). The value is added using grl_data_add* instead of grl_data_set ().

After implementing these, I was just a step away from allowing lua sources to have self registering keys. The only work left was to modify lua plugins to use the above functions when metadata is added to GrlMedia.

Now, adding self registering keys was as easy as typing

    if game.Developer then
      media.developer = game.Developer.xml
    end

Lastly, I added a test case to grilo-plugins to verify these changes. With this, allowing self registering keys to Grilo was over.

Adding Developer & Publisher to Games

GNOME Games currently has a very basic UI. I added Developer & Publisher to Game object which will further be used for segregating games into different views, such as a Developer view allowing users to select games from a particular developer and similarly a Publisher view. I’ve already started working on this and will be posting more on this soon.

I hope to see you all at GUADEC this year. Cheers!