menu_driver is the workhorse of the menus subsystem.
It checks to determine whether
the character c is a menu request or data.
If c is a request, the menu driver executes the request
and reports the result.
If c is data (a printable ASCII character), it enters the data
into the pattern buffer and tries to find a matching item.
If no match is found, the menu driver deletes
the character from the pattern buffer
and returns E_NO_MATCH.
If the character is not
recognized, the menu driver assumes it is an application-defined
command and returns E_UNKNOWN_COMMAND.
Menu driver requests:
Move left to an item.
Move right to an item.
Move up to an item.
Move down to an item.
Scroll up a line.
Scroll down a line.
Scroll up a page.
Scroll down a page.
Move to the first item.
Move to the last item.
Move to the next item.
Move to the previous item.
Select/de-select an item.
Clear the menu pattern buffer.
Delete the previous character from pattern buffer.
Move the next matching item.
Move to the previous matching item.
menu_driver returns one of the following:
The routine returned successfully.
An incorrect argument was passed to the routine.
The routine was called from an initialization or termination function.
The menu has not been posted.
An unknown request was passed to the menu driver.
The character failed to match.
The item cannot be selected.
The menu driver could not process the request.
Application defined commands should be defined relative to (greater than)
MAX_COMMAND, the maximum value of a request listed above.
The header file menu.h automatically includes the header files
eti.h and ocurses.h.