Change multi sort action

kazumit

Hi All,

About multi columns sorting,
My customer want to change multi columns sort action because
they feel 'Shift + Click' action is little confuse to end user and
they want to change to three step action asc, desc and off.

I checked source code and found '_fnSortListener' may handle multi sorting but I have no idea to customize,
please give me some advice to customize sort action.

Regards,
Takano