remind me:
5 windows, left/mid/right/status/notice
1 thread to get time and flush status bar every 60 sec
mainly 2 abstraction
WIDGET <- menu/form
menu_t <- menu attributes
only 1 interact()
widget->direct widget->enter, kinda OO like vfs
wgetch/menu_driver/form_driver/item_userptr/field_userptr, lib func
wgetch -> interact -> direct/enter -> driver/userptr
stack to store bill items for the sake of unsubscription
every decode() updates acc/stocks fields in db
sure() just updates table bill according to all TOTALs