If the application has specified the gact_relverify activation flag, it
will be sent an idcmp_gadgetup message when the gadget is properly
deactivated.  This happens when Return or Enter is pressed, when tabbing
to the next string gadget (where supported), and when a custom string
editing hook returns sga_end.

The gadget may become inactive without the application receiving an
idcmp_gadgetup message.  this will happen if the user performs some other
operation with the mouse or if another window is activated.  The gadget
may still contain updated, valid information even though the
IDCMP_GADGETUP message was not received.