This attribute tells strgclass that this gadget is a plain string gadget.
The attribute points to a string which the object copies into the string
gadget's current string value buffer.

When a strgclass gadget's internal STRINGA_LongVal or STRINGA_TextVal
value changes (usually because the user manipulated the gadget), it sends
itself an OM_NOTIFY message.  The OM_NOTIFY message will contain two
attribute/value pairs, GA_ID and either STRINGA_LongVal or STRINGA_TextVal
(depending on what kind of strgclass gadget it is).  Strgclass gadgets
only send a final OM_NOTIFY message (one's with the OPUF_INTERIM flag of
the opUpdate.opu_Flags field cleared).