C and dbus dictionaries with glib - c

Question

I'm currently building a program which needs to interface with the d-bus. I'm using the glib dbus library. I have a method that returns a dbus dictionary type, like this:
array [
dict entry(
string "Metadata"
variant array [
dict entry(
string "mpris:artUrl"
variant string "http://open.spotify.com/thumb/05e9ad92c22953e6c778536613605b67faa5a095"
)
dict entry(
string "mpris:length"
variant uint64 238000000
)
My question is, how on earth do I get this in my C program? I've tried the usual `dbus_g_proxy_connect_signal´ with a registered marshaller without much luck!
Edit: I've added some sample code (Which is not working, but does compile)
#include <string.h>
#include <glib.h>
#include <dbus/dbus.h>
#include <dbus/dbus-glib.h>
#define DBUS_SERVICE "com.spotify.qt"
#define DBUS_PATH "/"
#define DBUS_INTERFACE "org.freedesktop.MediaPlayer2"
#define DBUS_TYPE_G_STRING_VALUE_HASHTABLE (dbus_g_type_get_map ("GHashTable", G_TYPE_STRING, G_TYPE_VALUE))
//Global bus connection
DBusGConnection *bus;
DBusGProxy *proxy;
//Main gloop
GMainLoop *loop = NULL;
//Callback function.
static void callbackfunc(DBusGProxy *player_proxy, GHashTable *table){
GValue *value;
/* fetch values from hash table */
value = (GValue *) g_hash_table_lookup(table, "artist");
if (value != NULL && G_VALUE_HOLDS_STRING(value)) {
g_print("\nArtist: %s\n",g_value_get_string(value));
}
value = (GValue *) g_hash_table_lookup(table, "album");
if (value != NULL && G_VALUE_HOLDS_STRING(value)) {
g_print("\nAlbum: %s\n",g_value_get_string(value));
}
value = (GValue *) g_hash_table_lookup(table, "title");
if (value != NULL && G_VALUE_HOLDS_STRING(value)) {
g_print("\nTitle: %s\n",g_value_get_string(value));
}
}
int main (int argc, char **argv){
GError *error = NULL;
g_type_init ();
/* Get (on) the bus :p */
bus = dbus_g_bus_get (DBUS_BUS_SESSION, &error);
if (bus == NULL) {
g_printerr("Failed to open connection to bus: %s", error->message);
g_error_free(error);
return -1;
}
/* Create a proxy object for the bus driver */
proxy = dbus_g_proxy_new_for_name (bus,
DBUS_SERVICE,
DBUS_PATH,
DBUS_INTERFACE);
if (!proxy) {
g_printerr("Couldn't connect: %s", error->message);
g_error_free(error);
return -1;
}
/* Create the main loop instance */
loop = g_main_loop_new (NULL, FALSE);
dbus_g_proxy_add_signal(proxy, "GetMetadata",
DBUS_TYPE_G_STRING_VALUE_HASHTABLE, G_TYPE_INVALID);
dbus_g_proxy_connect_signal(proxy, "GetMetadata",
G_CALLBACK(callbackfunc), NULL, NULL);
g_print("Going into main function\n");
/* Main loop */
g_main_loop_run (loop);
return 0;
}

Answer 1

I'm going to port my code to use GIO rather than glib-dbus, I did how ever manage to get it working with glib-dbus using this:
if (dbus_g_proxy_call(p_proxy_md, "GetMetadata", NULL, G_TYPE_INVALID, DBUS_TYPE_G_STRING_VALUE_HASHTABLE, &table, G_TYPE_INVALID)) {
value = (GValue *) g_hash_table_lookup(table, "xesam:title");
sprintf(currentTrack.trackname,"%s",g_value_get_string(value));
value = (GValue *) g_hash_table_lookup(table, "xesam:album");
sprintf(currentTrack.album,"%s",g_value_get_string(value));
tmp = g_hash_table_lookup(table, "xesam:artist");
if (tmp != NULL)
{
GStrv strv = g_value_get_boxed(g_hash_table_lookup(table, "xesam:artist"));
sprintf(currentTrack.artist,"%s",*strv);
}
}
sprintf(notifybody,"By %s on %s",currentTrack.artist,currentTrack.album);
music_noti = notify_notification_new(currentTrack.trackname,notifybody, NULL);
notify_notification_set_timeout(music_noti,1500);
notify_notification_set_icon_from_pixbuf(music_noti, notifyicon);
notify_notification_show(music_noti, NULL);
notify_uninit();
}

Answer 2

Without using GLIB or any external library, the best way I've found is outlined in this post.
It requires knowing the structure of the datatype ahead of time, which is a bit annoying. However, you can use dbus-monitor to see what DBUS is sending first. Then you have to make an iterator for each level of the array. See the DBUS message documentation for how to use the iterators.