Sorting by "Display value" does not work for non-Latin characters

Hi Eugene,

Your explanation was very good - thanks for your time helping me figuring out how to do it, I appreciate it.

For documentation, I add here my code.

Here is the hook overriding where I map my callback function and the implementation of the callback function.

/**
 * Implements hook_facetapi_sort_info_alter().
 */
function facetapicustom_facetapi_sort_info_alter(array &$sort_info) {
	$sort_info['display']['callback'] = 'facetapicustom_sort_display';
}

// Copied and changed from module facetapi/plugins/facetapi/widget.inc
function facetapicustom_sort_display(array $a, array $b) {
	$a_display = (isset($a['#markup'])) ? $a['#markup'] : '';
	$b_display = (isset($b['#markup'])) ? $b['#markup'] : '';

	if ($a_display == $b_display) {
		return 0;
	}

	 $a_display = lib_string_remove_diacritics($a_display);
	 $b_display = lib_string_remove_diacritics($b_display);

	return strcasecmp($a_display, $b_display);
}

Here is a simple helper function that I have put in my custom library:

function lib_string_remove_diacritics($string) {
    return str_ireplace(
    	array('Ā', 'Ī', 'ṇ', 'Ṛ', 'Ś', 'ṣ', 'Ṭ'), 
    	array('A', 'I', 'N', 'R', 'S', 'S', 'T'), 
    	$string);
}

I would note that I did try to convert to different encoding but it was getting complicated, so a simple replacing of characters was easier.

Thanks again.