Add `dbus_get_prop_async` utility

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

4 files changed, 137 insertions, 293 deletions

diff --git a/include/swaybar/tray/dbus.h b/include/swaybar/tray/dbus.h
index 51754464..125ce96f 100644
--- a/include/swaybar/tray/dbus.h
+++ b/include/swaybar/tray/dbus.h
@@ -12,6 +12,23 @@ extern DBusConnection *conn;
 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 (will not necessarily arrive)
+ * and false otherwise
+ *
+ * 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),
+                void *data);
+/**
  * Should be called in main loop to dispatch events
  */
 void dispatch_dbus();
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;
diff --git a/swaybar/tray/sni.c b/swaybar/tray/sni.c
index 401a0091..200422da 100644
--- a/swaybar/tray/sni.c
+++ b/swaybar/tray/sni.c
@@ -14,6 +14,9 @@
 #include "client/cairo.h"
 #include "log.h"
 
+static const char *KDE_IFACE = "org.kde.StatusNotifierItem";
+static const char *FD_IFACE = "org.freedesktop.StatusNotifierItem";
+
 // Not sure what this is but cairo needs it.
 static const cairo_user_data_key_t cairo_user_data_key;
 
@@ -38,57 +41,19 @@ void sni_icon_ref_free(struct sni_icon_ref *sni_ref) {
 }
 
 /* Gets the pixmap of an icon */
-static void reply_icon(DBusPendingCall *pending, void *_data) {
+static void reply_icon(DBusMessageIter *iter /* a(iiay) */, void *_data) {
         struct StatusNotifierItem *item = _data;
 
-        DBusMessage *reply = dbus_pending_call_steal_reply(pending);
-
-        if (!reply) {
-                sway_log(L_ERROR, "Did not get reply");
-                goto bail;
-        }
-
-        int message_type = dbus_message_get_type(reply);
-
-        if (message_type == DBUS_MESSAGE_TYPE_ERROR) {
-                char *msg;
-
-                dbus_message_get_args(reply, NULL,
-                                DBUS_TYPE_STRING, &msg,
-                                DBUS_TYPE_INVALID);
-
-                sway_log(L_ERROR, "Message is error: %s", msg);
-                goto bail;
-        }
-
-        DBusMessageIter iter;
-        DBusMessageIter variant; /* v[a(iiay)] */
-        DBusMessageIter array; /* a(iiay) */
         DBusMessageIter d_struct; /* (iiay) */
         DBusMessageIter icon; /* ay */
 
-        dbus_message_iter_init(reply, &iter);
-
-        // Each if here checks the types above before recursing
-        if (dbus_message_iter_get_arg_type(&iter) != DBUS_TYPE_VARIANT) {
-                sway_log(L_ERROR, "Icon relpy type incorrect");
-                goto bail;
-        }
-        dbus_message_iter_recurse(&iter, &variant);
-
-        if (dbus_message_iter_check_signature(&variant, "a(iiay)")) {
-                sway_log(L_ERROR, "Icon relpy type incorrect");
-                goto bail;
-        }
-
-        if (dbus_message_iter_get_element_count(&variant) == 0) {
+        if (dbus_message_iter_get_element_count(iter) == 0) {
                 // Can't recurse if there are no items
                 sway_log(L_INFO, "Item has no icon");
-                goto bail;
+                return;
         }
-        dbus_message_iter_recurse(&variant, &array);
 
-        dbus_message_iter_recurse(&array, &d_struct);
+        dbus_message_iter_recurse(iter, &d_struct);
 
         int width;
         dbus_message_iter_get_basic(&d_struct, &width);
@@ -102,13 +67,13 @@ static void reply_icon(DBusPendingCall *pending, void *_data) {
 
         if (!len) {
                 sway_log(L_ERROR, "No icon data");
-                goto bail;
+                return;
         }
 
         // Also implies len % 4 == 0, useful below
         if (len != width * height * 4) {
                 sway_log(L_ERROR, "Incorrect array size passed");
-                goto bail;
+                return;
         }
 
         dbus_message_iter_recurse(&d_struct, &icon);
@@ -117,7 +82,7 @@ static void reply_icon(DBusPendingCall *pending, void *_data) {
         // FIXME support a variable stride
         // (works on my machine though for all tested widths)
         if (!sway_assert(stride == width * 4, "Stride must be equal to byte length")) {
-                goto bail;
+                return;
         }
 
         // Data is by reference, no need to free
@@ -127,7 +92,7 @@ static void reply_icon(DBusPendingCall *pending, void *_data) {
         uint8_t *image_data = malloc(stride * height);
         if (!image_data) {
                 sway_log(L_ERROR, "Could not allocate memory for icon");
-                goto bail;
+                return;
         }
 
         // Transform from network byte order to host byte order
@@ -155,97 +120,22 @@ static void reply_icon(DBusPendingCall *pending, void *_data) {
                 item->dirty = true;
                 dirty = true;
 
-                dbus_message_unref(reply);
-                dbus_pending_call_unref(pending);
                 return;
         } else {
                 sway_log(L_ERROR, "Could not create image surface");
                 free(image_data);
         }
 
-bail:
-        if (reply) {
-                dbus_message_unref(reply);
-        }
-        dbus_pending_call_unref(pending);
         sway_log(L_ERROR, "Could not get icon from item");
         return;
 }
-static void send_icon_msg(struct StatusNotifierItem *item) {
-        DBusPendingCall *pending;
-        DBusMessage *message = dbus_message_new_method_call(
-                        item->name,
-                        item->object_path,
-                        "org.freedesktop.DBus.Properties",
-                        "Get");
-        const char *iface;
-        if (item->kde_special_snowflake) {
-                iface = "org.kde.StatusNotifierItem";
-        } else {
-                iface = "org.freedesktop.StatusNotifierItem";
-        }
-        const char *prop = "IconPixmap";
-
-        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 item icon");
-                return;
-        }
-
-        dbus_pending_call_set_notify(pending, reply_icon, item, NULL);
-}
 
 /* Get an icon by its name */
-static void reply_icon_name(DBusPendingCall *pending, void *_data) {
+static void reply_icon_name(DBusMessageIter *iter, void *_data) {
         struct StatusNotifierItem *item = _data;
 
-        DBusMessage *reply = dbus_pending_call_steal_reply(pending);
-
-        if (!reply) {
-                sway_log(L_INFO, "Got no icon name reply from item");
-                goto bail;
-        }
-
-        int message_type = dbus_message_get_type(reply);
-
-        if (message_type == DBUS_MESSAGE_TYPE_ERROR) {
-                char *msg;
-
-                dbus_message_get_args(reply, NULL,
-                                DBUS_TYPE_STRING, &msg,
-                                DBUS_TYPE_INVALID);
-
-                sway_log(L_INFO, "Could not get icon name: %s", msg);
-                goto bail;
-        }
-
-        DBusMessageIter iter; /* v[s] */
-        DBusMessageIter variant; /* s */
-
-        dbus_message_iter_init(reply, &iter);
-        if (dbus_message_iter_get_arg_type(&iter) != DBUS_TYPE_VARIANT) {
-                sway_log(L_ERROR, "Icon name relpy type incorrect");
-                goto bail;
-        }
-        dbus_message_iter_recurse(&iter, &variant);
-
-
-        if (dbus_message_iter_get_arg_type(&variant) != DBUS_TYPE_STRING) {
-                sway_log(L_ERROR, "Icon name relpy type incorrect");
-                goto bail;
-        }
-
         char *icon_name;
-        dbus_message_iter_get_basic(&variant, &icon_name);
+        dbus_message_iter_get_basic(iter, &icon_name);
 
         cairo_surface_t *image = find_icon(icon_name, 256);
 
@@ -259,55 +149,19 @@ static void reply_icon_name(DBusPendingCall *pending, void *_data) {
                 item->dirty = true;
                 dirty = true;
 
-                dbus_message_unref(reply);
-                dbus_pending_call_unref(pending);
                 return;
         }
 
-bail:
-        if (reply) {
-                dbus_message_unref(reply);
-        }
-        dbus_pending_call_unref(pending);
         // Now try the pixmap
-        send_icon_msg(item);
-        return;
-}
-static void send_icon_name_msg(struct StatusNotifierItem *item) {
-        DBusPendingCall *pending;
-        DBusMessage *message = dbus_message_new_method_call(
-                        item->name,
-                        item->object_path,
-                        "org.freedesktop.DBus.Properties",
-                        "Get");
-        const char *iface;
-        if (item->kde_special_snowflake) {
-                iface = "org.kde.StatusNotifierItem";
-        } else {
-                iface = "org.freedesktop.StatusNotifierItem";
-        }
-        const char *prop = "IconName";
-
-        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 item icon name");
-                return;
-        }
-
-        dbus_pending_call_set_notify(pending, reply_icon_name, item, NULL);
+        dbus_get_prop_async(item->name, item->object_path,
+                (item->kde_special_snowflake ? KDE_IFACE : FD_IFACE),
+                "IconPixmap", "a(iiay)", reply_icon, item);
 }
 
 void get_icon(struct StatusNotifierItem *item) {
-        send_icon_name_msg(item);
+        dbus_get_prop_async(item->name, item->object_path,
+                (item->kde_special_snowflake ? KDE_IFACE : FD_IFACE),
+                "IconName", "s", reply_icon_name, item);
 }
 
 void sni_activate(struct StatusNotifierItem *item, uint32_t x, uint32_t y) {
diff --git a/swaybar/tray/tray.c b/swaybar/tray/tray.c
index f1ecb429..89e7c3e2 100644
--- a/swaybar/tray/tray.c
+++ b/swaybar/tray/tray.c
@@ -38,47 +38,13 @@ static void register_host(char *name) {
         dbus_message_unref(message);
 }
 
-static void get_items_reply(DBusPendingCall *pending, void *_data) {
-        DBusMessage *reply = dbus_pending_call_steal_reply(pending);
-
-        if (!reply) {
-                sway_log(L_ERROR, "Got no items reply from sni watcher");
-                goto bail;
-        }
-
-        int message_type = dbus_message_get_type(reply);
-
-        if (message_type == DBUS_MESSAGE_TYPE_ERROR) {
-                char *msg;
-
-                dbus_message_get_args(reply, NULL,
-                                DBUS_TYPE_STRING, &msg,
-                                DBUS_TYPE_INVALID);
-
-                sway_log(L_ERROR, "Message is error: %s", msg);
-                goto bail;
-        }
-
-        DBusMessageIter iter;
-        DBusMessageIter variant;
+static void get_items_reply(DBusMessageIter *iter, void *_data) {
         DBusMessageIter array;
 
-        dbus_message_iter_init(reply, &iter);
-        if (dbus_message_iter_get_arg_type(&iter) != DBUS_TYPE_VARIANT) {
-                sway_log(L_ERROR, "Replyed with wrong type, not v(as)");
-                goto bail;
-        }
-        dbus_message_iter_recurse(&iter, &variant);
-        if (dbus_message_iter_get_arg_type(&variant) != DBUS_TYPE_ARRAY ||
-                        dbus_message_iter_get_element_type(&variant) != DBUS_TYPE_STRING) {
-                sway_log(L_ERROR, "Replyed with wrong type, not v(as)");
-                goto bail;
-        }
-
         // O(n) function, could be faster dynamically reading values
-        int len = dbus_message_iter_get_element_count(&variant);
+        int len = dbus_message_iter_get_element_count(iter);
 
-        dbus_message_iter_recurse(&variant, &array);
+        dbus_message_iter_recurse(iter, &array);
         for (int i = 0; i < len; i++) {
                 const char *name;
                 dbus_message_iter_get_basic(&array, &name);
@@ -93,52 +59,14 @@ static void get_items_reply(DBusPendingCall *pending, void *_data) {
                         }
                 }
         }
-
-bail:
-        dbus_message_unref(reply);
-        dbus_pending_call_unref(pending);
-        return;
 }
-static void get_obj_items_reply(DBusPendingCall *pending, void *_data) {
-        DBusMessage *reply = dbus_pending_call_steal_reply(pending);
-
-        if (!reply) {
-                sway_log(L_ERROR, "Got no object path items reply from sni watcher");
-                goto bail;
-        }
-
-        int message_type = dbus_message_get_type(reply);
-
-        if (message_type == DBUS_MESSAGE_TYPE_ERROR) {
-                char *msg;
-
-                dbus_message_get_args(reply, NULL,
-                                DBUS_TYPE_STRING, &msg,
-                                DBUS_TYPE_INVALID);
-
-                sway_log(L_ERROR, "Message is error: %s", msg);
-                goto bail;
-        }
-
-        DBusMessageIter iter;
-        DBusMessageIter variant;
+static void get_obj_items_reply(DBusMessageIter *iter, void *_data) {
         DBusMessageIter array;
         DBusMessageIter dstruct;
 
-        dbus_message_iter_init(reply, &iter);
-        if (dbus_message_iter_get_arg_type(&iter) != DBUS_TYPE_VARIANT) {
-                sway_log(L_ERROR, "Replyed with wrong type, not v(a(os))");
-                goto bail;
-        }
-        dbus_message_iter_recurse(&iter, &variant);
-        if (dbus_message_iter_check_signature(&iter, "a(os)")) {
-                sway_log(L_ERROR, "Replyed with wrong type not a(os)");
-                goto bail;
-        }
-
-        int len = dbus_message_iter_get_element_count(&variant);
+        int len = dbus_message_iter_get_element_count(iter);
 
-        dbus_message_iter_recurse(&variant, &array);
+        dbus_message_iter_recurse(iter, &array);
         for (int i = 0; i < len; i++) {
                 const char *object_path;
                 const char *unique_name;
@@ -164,10 +92,6 @@ static void get_obj_items_reply(DBusPendingCall *pending, void *_data) {
                         }
                 }
         }
-
-bail:
-        dbus_message_unref(reply);
-        dbus_pending_call_unref(pending);
 }
 
 static void get_items() {
@@ -176,52 +100,13 @@ static void get_items() {
         list_free(tray->items);
         tray->items = create_list();
 
-        DBusPendingCall *pending;
-        DBusMessage *message = dbus_message_new_method_call(
-                        "org.freedesktop.StatusNotifierWatcher",
-                        "/StatusNotifierWatcher",
-                        "org.freedesktop.DBus.Properties",
-                        "Get");
-
-        const char *iface = "org.freedesktop.StatusNotifierWatcher";
-        const char *prop = "RegisteredStatusNotifierItems";
-        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 items");
-                return;
-        }
-
-        dbus_pending_call_set_notify(pending, get_items_reply, NULL, NULL);
+        dbus_get_prop_async("org.freedesktop.StatusNotifierWatcher",
+                "/StatusNotifierWatcher","org.freedesktop.StatusNotifierWatcher",
+                "RegisteredStatusNotifierItems", "as", get_items_reply, NULL);
 
-        message = dbus_message_new_method_call(
-                        "org.freedesktop.StatusNotifierWatcher",
-                        "/StatusNotifierWatcher",
-                        "org.freedesktop.DBus.Properties",
-                        "Get");
-
-        iface = "org.swaywm.LessSuckyStatusNotifierWatcher";
-        prop = "RegisteredObjectPathItems";
-        dbus_message_append_args(message,
-                        DBUS_TYPE_STRING, &iface,
-                        DBUS_TYPE_STRING, &prop,
-                        DBUS_TYPE_INVALID);
-
-        status = dbus_connection_send_with_reply(conn, message, &pending, -1);
-        dbus_message_unref(message);
-
-        if (!(pending || status)) {
-                sway_log(L_ERROR, "Could not get items");
-                return;
-        }
-        dbus_pending_call_set_notify(pending, get_obj_items_reply, NULL, NULL);
+        dbus_get_prop_async("org.freedesktop.StatusNotifierWatcher",
+                "/StatusNotifierWatcher","org.swaywm.LessSuckyStatusNotifierWatcher",
+                "RegisteredObjectPathItems", "a(os)", get_obj_items_reply, NULL);
 }
 
 static DBusHandlerResult signal_handler(DBusConnection *connection,