toNumberAdvanced = function( numeric, fallback ) {
            if ( typeof numeric !== "string" ) {
                return toNumber( numeric, fallback );
            }
            var ratio = numeric.match( /^([+-]*[\d\.]+)([wh])$/ );
            if ( ratio == null ) {
                return toNumber( numeric, fallback );
            } else {
                var value = parseFloat( ratio[ 1 ] );
                var config = window.impress.getConfig();
                var multiplier = ratio[ 2 ] === "w" ? config.width : config.height;
                return value * multiplier;
            }
        }
Extends toNumber() to correctly compute also relative-to-screen-size values 5w and 5h.

Returns the computed value in pixels with w/h postfix removed.