1. A method for determining a total dimension of items in a computer-based user interface control, the method comprising: determining one or more known item dimensions comprising one or more of: determining a dimension of one or more realized items; determining a dimension of previously realized items; and determining a viewport offset dimension value; determining one or more values for amounts of known items comprising one or more of: 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 known items, comprising combining one or more known item dimensions with one or more values for amounts of known items; and: generating a total dimension value comprising combining the estimated dimension value with a total number of items.