+ If @a value is non-empty, it will be shown in the text entry part of
+ the control and if it has numeric value, the initial numeric value of
+ the control, as returned by GetValue() will also be determined by it
+ instead of by @a initial. Hence, it only makes sense to specify @a
+ initial if @a value is an empty string or is not convertible to a
+ number, otherwise @a initial is simply ignored and the number specified
+ by @a value is used.
+