In epiphany, I wanted to limit the number of matches drawn, since the completion can't be told to call match_func ONLY until N matches are found, I wrapped my match_func with a count, so after N return values that were 'TRUE' i will return FALSE before anything happens, like this:

static gboolean
match_func_wrapper (GtkEntryCompletion *completion,
                const char *key,
                GtkTreeIter *iter,
                gpointer data)
{
        gboolean ret = FALSE;
        EphyLocationEntryPrivate *priv = ((EphyLocationEntry *) data)->priv;

        if (priv->matches_count > MAX_MATCHES)
                return FALSE;

        ret = priv->match_func(completion, key, iter, data);

        if (ret)
                priv->matches_count++;

        return ret;
}

Yes yes, matches_count begins as 0 and etc etc, this is just the real life snippet i wanted to show, I'm attaching a python testcase that shows the bug.

The bug: after adding this "early return", the completion popup held only 1 result no matter there were more matches. Only in the second loop of match_func it would show all the MAX_MATCHES matches. Like this:

User types: 'e':
| e                |
-------------------
  |http://e.com    |
  -----------------

User deletes 'e', types 'e' again:
| e                |
-------------------
  |http://e.com    |
  |http://e2.com   |
  |http://e3.com   |
  |http://e4.com   |
  |http://e5.com   |
  -----------------

See attached python test. Try writing 't' (that is supposed to show all the matches up to the set limit) and you'll see just 1 match, now delete and try again and you'll see N-1 matches, the last return True is being ignored.