Port swaybar tray files to 0.15 and fix compiling

include/swaybar/tray/dbus.h

@@ -5,6 +5,37 @@
 #include <dbus/dbus.h>
 extern DBusConnection *conn;
 
+enum property_status {
+	PROP_EXISTS, /* Will give iter */
+	PROP_ERROR, /* Will not give iter */
+	PROP_BAD_DATA, /* Will not give iter */
+	PROP_WRONG_SIG, /* Will give iter, please be careful */
+};
+
+/**
+ * Checks the signature of the given iter against `sig`. Prefer to
+ * `dbus_message_iter_get_signature` as this one frees the intermediate string.
+ */
+bool dbus_message_iter_check_signature(DBusMessageIter *iter, const char *sig);
+
+/**
+ * Fetches the property and calls `callback` with a message iter pointing it.
+ * Performs error handling and signature checking.
+ *
+ * Returns: true if message is successfully sent and false otherwise. If there
+ * is an error getting a property, `callback` will still be run, but with
+ * `status` set to the error.
+ *
+ * NOTE: `expected_signature` must remain valid until the message reply is
+ * received, please only use 'static signatures.
+ */
+bool dbus_get_prop_async(const char *destination,
+		const char *path,
+		const char *iface,
+		const char *prop,
+		const char *expected_signature,
+		void(*callback)(DBusMessageIter *iter, void *data, enum property_status status),
+		void *data);
 /**
  * Should be called in main loop to dispatch events
  */