Having trouble figuring out calling conventions

xdosearch.p6

   use NativeCall;

   class Xdo is export {
       has Pointer $.id is rw;

       submethod BUILD {
           sub xdo_new(Str) returns Pointer is native('xdo') { * }
           self.id = xdo_new('');
       }

       method version() {
           sub xdo_version() returns Str is encoded('utf8') is native('xdo') { * }
           xdo_version()
       }


       #`[
       Search for windows.

              search: the search query.
       * @param windowlist_ret the list of matching windows to return
       * @param nwindows_ret the number of windows (length of windowlist_ret)
       * @see xdo_search_t

       see https://github.com/jordansissel/xdotool/blob/master/xdo.h#L168
       for details of xdo_search_t structure


       */
      int xdo_search_windows(const xdo_t *xdo, const xdo_search_t *search,
                            Window **windowlist_ret, unsigned int *nwindows_ret);
       ]
       # search bitmask bits
       #define SEARCH_TITLE       (1UL << 0) DEPRECATED - Use SEARCH_NAME
       #define SEARCH_CLASS       (1UL << 1)
       #define SEARCH_NAME        (1UL << 2)
       #define SEARCH_PID         (1UL << 3)
       #define SEARCH_ONLYVISIBLE (1UL << 4)
       #define SEARCH_SCREEN      (1UL << 5)
       #define SEARCH_CLASSNAME   (1UL << 6)
       #define SEARCH_DESKTOP     (1UL << 7)

        class Query is repr('CStruct') {
            has str   $.title;            # regex pattern to test against a window title
            has str   $.winclass;         # regex pattern to test against a window class
            has str   $.winclassname;     # regex pattern to test against a window class
            has str   $.winname;          # regex pattern to test against a window name
            has int   $.pid;              # window pid (From window atom _NET_WM_PID)
            has long  $.max_depth = 1;    # depth of search. 1 means only toplevel windows
            has int   $.only_visible = 1; # boolean; set true to search only visible windows
            has int   $.screen;           # what screen to search, if any. If none given, search all

            # Should the tests be 'and' (0) or 'or' (1)? If 'and', any failure will skip the
            # window. If 'or', any success will keep the window in search results.
            has int   $.require = 0;

            # bitmask of things you are searching for, such as SEARCH_NAME, etc.
            # @see SEARCH_NAME, SEARCH_CLASS, SEARCH_PID, SEARCH_CLASSNAME, etc

            has long $.searchmask = 2;

            # What desktop to search, if any. If none given, search all screens. */
            has long $.desktop;

            # How many results to return? If 0, return all. */
            has uint32 $.limit = 0;
        }

        # Hard code a bunch of stuff for right now until I figure out the
        # correct calling conventions.
        method search-windows (str $string) {
            my $query = Query.new(:winname($string), :searchmask(2));
            #dd $query;
            my Pointer $ids;
            sub xdo_search_windows(Pointer, Query, Pointer, int32 ) returns int32 is native('xdo') { * };
            my int32 $n;
            say xdo_search_windows(self.id, $query, $ids, $n);
            $ids
       }
}

my $xdo = Xdo.new;
say 'libxdo version: ', $xdo.version, ' - loaded ok.';

say $xdo.search-windows('Firefox');

I'm trying to get the same results as the command line tool: E.G.

xdotool search --onlyvisible --maxdepth 1 --name "Firefox"