This plugin is not supported in the WS Api

[extorn]

Firstly, I've made this work by copying and pasting the pwg.categories methods verbartim into my plugin (PiwigoClientExt), then tweaking as below. I had to do this because unfortunately I couldn't see a way of accessing the details about the call (more than just source method name) from within the get_extended_desc method. This code will be released shortly if that will make the proposed fix clearer.

To support this, I propose the following alterations:
To the Piwigo Project
All calls to 'render_category_description' must have parameters changed to allow an array, allowing indication as to whether this item is the subject of the call or just a sub category within the subject (if a category id is provided to categories.getList, then that categoryId would be the subject. If none provided, then none will be the subject).

$render_params = array('isSubject' => $row['id'] == $params['cat_id'], 
                               'text' => $row['name']);

example call

trigger_change(
                    'render_category_name',
                    $row['name'],
                    'ws_categories_getList')
                );

To this project

function get_extended_desc($param1, $params)
{
    if (is_array($params)) {
        // This has been called by our code (It's a string if it hasn't)
        $extDescType = 'subcatify_category_description';
        if($params['isSubject']) {
            $extDescType = 'main_page_category_description';
        }
        return trigger_change(
            'render_category_description',
            $params['text'],
            $extDescType
            );
        //This category                 : main_page_category_description
        //Sub category summary version  : subcatify_category_description
    }
    // NOTE: $param1 is the caller method in the new code (because we pass the other data in the params object),
    //            but the raw description text in the Piwigo Team Code.
    return $param1;
}