GlideSPUserCriteria appears to be a way to use and check user criteria
for service portal records. This is dependent on the "Service Portal
User Criteria Support" plugin being activated, and the property,
"glide.service_portal.user_criteria_enabled".

isEnabled #

Returns true or false based on the value of
glide.service_portal.user_criteria_enabled. If the propery is "true"
than it retuns true, else it returns false.

userCanSeeInstance #

This expects a sys_id of a sp_instance record and then uses the user
critera records to determine visiblity.

userCanSeePage #

This expects a sys_id of a sp_page record and then uses the user
critera records to determine visiblity.

userCanSeeSearchSource #

This expects a sys_id of a sp_search_source record and then uses the
user critera records to determine visiblity.

This is the only function I could find in a OOB instance in the "Search
Page" widget server script near line 50.

var userCriteria = new GlideSPUserCriteria();
if (userCriteria.isEnabled()) {
if (!userCriteria.userCanSeeSearchSource(gr.getUniqueValue()))
return;
} else {
//...
}

userCanSeeWidget #

This expects a sys_id of a sp_widget record and then uses the user
critera records to determine visiblity.

Further Reading #