KEYPRESS_CB
Action generated when a key is pressed or released. If the key is pressed and held several calls will occur. It is called after the common callback K_ANY.
Callback
int function(Ihandle *self, int c, int press); [in C] elem:keypress_cb(c, press: number) -> (ret: number) [in Lua]self: identifier of the element.
c: identifier of typed key. Please refer to the Keyboard Codes table for a list of possible values.
press: 1 is the user pressed the key or 0 otherwise.This function may return IUP_CLOSE.