public function save_hints($formdata, $withparts = false) {
        global $DB;
        $context = $formdata->context;

        $oldhints = $DB->get_records('question_hints',
                array('questionid' => $formdata->id), 'id ASC');


        $numhints = $this->count_hints_on_form($formdata, $withparts);

        for ($i = 0; $i < $numhints; $i += 1) {
            if (html_is_blank($formdata->hint[$i]['text'])) {
                $formdata->hint[$i]['text'] = '';
            }

            if ($withparts) {
                $clearwrong = !empty($formdata->hintclearwrong[$i]);
                $shownumcorrect = !empty($formdata->hintshownumcorrect[$i]);
            }

            if ($this->is_hint_empty($formdata, $i, $withparts)) {
                continue;
            }

            // Update an existing hint if possible.
            $hint = array_shift($oldhints);
            if (!$hint) {
                $hint = new stdClass();
                $hint->questionid = $formdata->id;
                $hint->hint = '';
                $hint->id = $DB->insert_record('question_hints', $hint);
            }

            $hint->hint = $this->import_or_save_files($formdata->hint[$i],
                    $context, 'question', 'hint', $hint->id);
            $hint->hintformat = $formdata->hint[$i]['format'];
            if ($withparts) {
                $hint->clearwrong = $clearwrong;
                $hint->shownumcorrect = $shownumcorrect;
            }
            $hint->options = $this->save_hint_options($formdata, $i, $withparts);
            $DB->update_record('question_hints', $hint);
        }

        // Delete any remaining old hints.
        $fs = get_file_storage();
        foreach ($oldhints as $oldhint) {
            $fs->delete_area_files($context->id, 'question', 'hint', $oldhint->id);
            $DB->delete_records('question_hints', array('id' => $oldhint->id));
        }
    }

    /**
     * Count number of hints on the form.
     * Overload if you use custom hint controls.
     */
    protected function count_hints_on_form($formdata, $withparts) {
        if (!empty($formdata->hint)) {
            $numhints = max(array_keys($formdata->hint)) + 1;
        } else {
            $numhints = 0;
        }

        if ($withparts) {
            if (!empty($formdata->hintclearwrong)) {
                $numclears = max(array_keys($formdata->hintclearwrong)) + 1;
            } else {
                $numclears = 0;
            }
            if (!empty($formdata->hintshownumcorrect)) {
                $numshows = max(array_keys($formdata->hintshownumcorrect)) + 1;
            } else {
                $numshows = 0;
            }
            $numhints = max($numhints, $numclears, $numshows);
        }
        return $numhints;
    }

    /**
     * Determine if the hint with specified number is not empty and should be saved.
     * Overload if you use custom hint controls.
     */
    protected function is_hint_empty($formdata, $number, $withparts) {
        if ($withparts) {
            return empty($formdata->hint[$number]['text']) && empty($formdata->hintclearwrong[$number]) &&
                    empty($formdata->hintshownumcorrect[$number]);
        } else {
            return  empty($formdata->hint[$number]['text']);
        }
    }

    /**
     * Save additional question type data into the hint optional field.
     * Overload if you use custom hint information.
     */
    protected function save_hint_options($formdata, $number, $withparts) {
        return null;//By default, options field is unused.
    }