private ContentToken evaluateFunction(final CSSFunctionValue function,
final LayoutProcess process,
final LayoutElement element)
{
final StyleValueFunction styleFunction =
FunctionFactory.getInstance().getStyleFunction(function.getFunctionName());
try
{
final CSSValue value = styleFunction.evaluate(process, element, function);
if (value instanceof CSSResourceValue)
{
final CSSResourceValue refValue = (CSSResourceValue) value;
return new ResourceContentToken(refValue.getValue());
}