Implement a command to travel the focusstack. This can be used like a jumpback.

However, it is a bit more flexible obviously. You can specify the
offset of the window you want to go to, to implement workflows like
the following:
 * Jump to mutt
 * Jump to irssi
 * Jump back ("focus 2" would be the command)

src/handlers.c

@@ -837,7 +837,7 @@ int handle_windowclass_change(void *data, xcb_connection_t *conn, uint8_t state,
                 LOG("prop == NULL\n");
                 return 1;
         }
-        Client *client = table_get(byChild, window);
+        Client *client = table_get(&by_child, window);
         if (client == NULL)
                 return 1;
         char *new_class;