5.5.3.3 The menu driver

Procedure: menu-driver menu c

Once a menu has been posted (displayed), you should funnel input events to it through menu-driver. This routine has three major input cases:

• The input is a form navigation request. Navigation request codes are constants defined in the table below, which are distinct from the key and character codes returned by wgetch.
• The input is a printable character. Printable characters (which must be positive, less than 256) are checked according to the program’s locale settings.
• The input is the KEY_MOUSE special key associated with an mouse event.

The menu driver request are as follows.

REQ_LEFT_ITEM

Move left to an item.

REQ_RIGHT_ITEM

Move right to an item.

REQ_UP_ITEM

Move up to an item.

REQ_DOWN_ITEM

Move down to an item.

REQ_SCR_ULINE

Scroll up a line.

REQ_SCR_DLINE

Scroll down a line.

REQ_SCR_DPAGE

Scroll down a page.

REQ_SCR_UPAGE

Scroll up a page.

REQ_FIRST_ITEM

Move to the first item.

REQ_LAST_ITEM

Move to the last item.

REQ_NEXT_ITEM

Move to the next item.

REQ_PREV_ITEM

Move to the previous item.

REQ_TOGGLE_ITEM

Select/deselect an item.

REQ_CLEAR_PATTERN

Clear the menu pattern buffer.

REQ_BACK_PATTERN

Delete the previous character from the pattern buffer.

REQ_NEXT_MATCH

Move to the next item matching the pattern match.

REQ_PREV_MATCH

Move to the previous item matching the pattern match.

If the second argument c is a printable character, the code appends it to the pattern buffer and attempts to move to the next item matching the new pattern. If there is no such match, menu-driver returns E_NO_MATCH and deletes the appended character from the buffer.

If the second argument c is one of the above pre-defined requests, the corresponding action is performed.

If the second argument is the KEY_MOUSE special key, the associated mouse event is translated into one of the above pre-defined requests. Currently only clicks in the user window (e.g. inside the menu display area or the decoration window) are handled.

If you click above the display region of the menu:

• a REQ_SCR_ULINE is generated for a single click,
• a REQ_SCR_UPAGE is generated for a double-click and
• a REQ_FIRST_ITEM is generated for a triple-click.

If you click below the display region of the menu:

• a REQ_SCR_DLINE is generated for a single click,
• a REQ_SCR_DPAGE is generated for a double-click and
• a REQ_LAST_ITEM is generated for a triple-click.

If you click at an item inside the display area of the menu:

• the menu cursor is positioned to that item.
• If you double-click an item a REQ_TOGGLE_ITEM is generated and E_UNKNOWN_COMMAND is returned. This return value makes sense, because a double click usually means that an item-specific action should be returned. It is exactly the purpose of this return value to signal that an application specific command should be executed.
• If a translation into a request was done, menu_driver returns the result of this request.

If you clicked outside the user window or the mouse event could not be translated into a menu request an E_REQUEST_DENIED is returned.

The procedure menu-driver returns one of the following error codes:

E_OK

The routine succeeded.

E_SYSTEM_ERROR

System error occurred (see errno).

E_BAD_ARGUMENT

Routine detected an incorrect or out-of-range argument.

E_BAD_STATE

Routine was called from an initialization or termination function.

E_NOT_POSTED

The menu has not been posted.

E_UNKNOWN_COMMAND

The menu driver code saw an unknown request code.

E_NO_MATCH

Character failed to match.

E_REQUEST_DENIED

The menu driver could not process the request.