The messages set with drupal_set_message() are saved in $_SESSION['messages'][$type] as an array of strings ($type can be "status", "warning", or "error"). The message you see, is set in poll_vote(), which is the form submission handler used for processing a vote, used from poll_view_voting(), the form builder for the vote form.
In order to remove the show string you should:
- Implement hook_form_FORM_ID_alter() to add a form submission handler that is executed after
poll_vote().
- Implement the form submission handler to remove the string added from
poll_vote().
Code similar to the following one should work.
function mymodule_form_poll_view_voting_alter(&$form, &$form_state) {
$form['vote']['#submit'][] = 'mymodule_poll_view_submit';
}
function mymodule_poll_view_submit($form, &$form_state) {
if (isset($_SESSION['messages']['status']) && is_array($_SESSION['messages']['status'])) {
$messages = array_flip($_SESSION['messages']['status']);
unset($messages[t('Your vote was recorded.')]);
$_SESSION['messages']['status'] = $messages;
}
}