1. A method for determining a total dimension of items in a computer-based user interface control, the method comprising: determining one or more item dimensions comprising: determining respective dimensions of one or more realized items; determining respective dimensions of one or more previously realized items; and determining a viewport offset dimension value for one or more viewport offset items; determining one or more amounts of at least some of the items comprising: determining an amount of realized items; determining an amount of previously realized items; and determining an amount of viewport offset items; determining an estimated dimension value for at least some of the items, comprising combining one or more of the item dimensions with one or more of the amounts of at least some of the items, determining the estimated dimension value comprising at least one of: determining an average dimension value for at least some of the items; determining a modal dimension value for at least some of the items; and determining a median dimension value for at least some of the items; and generating a total dimension value comprising combining the estimated dimension value with a total number of items, at least some of the method implemented at least in part via a processing unit.