The variables for that trigger are as follows.
Code:
$_PLUGINS->trigger( 'gj_onBeforeDisplayCategory', array( &$return, &$rows, &$category, &$counters, $user ) );
var1 is the return output (typically used to add extra HTML to the page), var2 is the groups in the category, var3 is the category object it self, var4 is used to add to the counter output in the canvas header, var5 is the current user object viewing the category (not exactly needed anymore). So if you want to condition against the category id you'd use [var3_id].
That trigger is listed on our triggers documentation page below. Use your browsers built in search functionality to search for a trigger, which shows the variables available to it.
www.joomlapolis.com/documentation/18358-using-cb-triggers
krileon
