Add `dbus_get_prop_async` utility

This drastically reduces the amount of boilerplate needed to get a
property from a bus object.

1 files changed, 89 insertions, 1 deletions

diff --git a/swaybar/tray/dbus.c b/swaybar/tray/dbus.c
index 46a1c807..4439fb83 100644
--- a/swaybar/tray/dbus.c
+++ b/swaybar/tray/dbus.c
@@ -136,7 +136,58 @@ static void dispatch_status(DBusConnection *connection, DBusDispatchStatus new_s
         }
 }
 
-/* Public functions below */
+struct async_prop_data {
+        char const *sig;
+        void(*callback)(DBusMessageIter *, void *);
+        void *usr_data;
+};
+
+static void get_prop_callback(DBusPendingCall *pending, void *_data) {
+        struct async_prop_data *data = _data;
+
+        DBusMessage *reply = dbus_pending_call_steal_reply(pending);
+
+        if (!reply) {
+                sway_log(L_INFO, "Got no icon name reply from item");
+                goto bail;
+        }
+
+        if (dbus_message_get_type(reply) == DBUS_MESSAGE_TYPE_ERROR) {
+                char *msg;
+
+                dbus_message_get_args(reply, NULL,
+                                DBUS_TYPE_STRING, &msg,
+                                DBUS_TYPE_INVALID);
+
+                sway_log(L_INFO, "Failure to get property: %s", msg);
+                goto bail;
+        }
+
+        DBusMessageIter iter;
+        DBusMessageIter variant;
+
+        dbus_message_iter_init(reply, &iter);
+        if (dbus_message_iter_get_arg_type(&iter) != DBUS_TYPE_VARIANT) {
+                sway_log(L_ERROR, "Property relpy type incorrect");
+                goto bail;
+        }
+        dbus_message_iter_recurse(&iter, &variant);
+
+        if (!dbus_message_iter_check_signature(&variant, data->sig)) {
+                sway_log(L_INFO, "Property returned has incorrect signatue.");
+                goto bail;
+        }
+
+        data->callback(&variant, data->usr_data);
+
+bail:
+        if (reply) {
+                dbus_message_unref(reply);
+        }
+        dbus_pending_call_unref(pending);
+}
+
+/* Public functions below -- see header for docs*/
 
 bool dbus_message_iter_check_signature(DBusMessageIter *iter, const char *sig) {
         char *msg_sig = dbus_message_iter_get_signature(iter);
@@ -145,6 +196,43 @@ bool dbus_message_iter_check_signature(DBusMessageIter *iter, const char *sig) {
         return (result == 0);
 }
 
+bool dbus_get_prop_async(const char *destination,
+                const char *path, const char *iface,
+                const char *prop, const char *expected_signature,
+                void(*callback)(DBusMessageIter *, void *), void *usr_data) {
+        struct async_prop_data *data = malloc(sizeof(struct async_prop_data));
+        if (!data) {
+                return false;
+        }
+        DBusPendingCall *pending;
+        DBusMessage *message = dbus_message_new_method_call(
+                        destination, path,
+                        "org.freedesktop.DBus.Properties",
+                        "Get");
+
+        dbus_message_append_args(message,
+                        DBUS_TYPE_STRING, &iface,
+                        DBUS_TYPE_STRING, &prop,
+                        DBUS_TYPE_INVALID);
+
+        bool status =
+                dbus_connection_send_with_reply(conn, message, &pending, -1);
+
+        dbus_message_unref(message);
+
+        if (!(pending || status)) {
+                sway_log(L_ERROR, "Could not get property");
+                return false;
+        }
+
+        data->sig = expected_signature;
+        data->callback = callback;
+        data->usr_data = usr_data;
+        dbus_pending_call_set_notify(pending, get_prop_callback, data, free);
+
+        return true;
+}
+
 void dispatch_dbus() {
         if (!should_dispatch || !conn) {
                 return;