how to get mode value of a customcontrol

when use
customcontrol c1，mode=1
igor sends a kcce_mode event to the call-back function.
the wmcustomcontrolaction struct has a member named mode, I think the mode value (here should be 1)would be found here. but that is not true: the mode seems always to be 0
It is said in the manual that mode is for general purpose, no further infomation.

does anyone know how to get mode value? or whether i have a misunderstanding?