4.15.11 The Form Driver: The Work Horse of the System

The form-driver procedure plays a very important role in the forms system. All types of requests to forms should be funneled through form-driver.

As you have seen some of the examples above, you have to be in a loop looking for user input and then decide whether it is a field data or a form request. The form requests are then passes to form-driver to do the work.

The requests roughly can be divided into the following categories. Different request and their usage is explained below.

4.15.11.1 Page Navigation Requests

These requests cause page-level moves through the form, triggering display of a new form screen. A form can be made of multiple pages. If you have a big form with lots of fields and logical sections, then you can divide the form into pages. The function set-new-page sets a new page at the field specified.

Also, the following requests, when passed to the form driver, all you to move to different pages.

• REQ_NEXT_PAGE Move to the next form page.
• REQ_PREV_PAGE Move to the previous form page.
• REQ_FIRST_PAGE Move to the first form page.
• REQ_LAST_PAGE Move to the last form page.

These are cyclic. The moving to the next page after the last page put you at the top.

4.15.11.2 Inter-Field Navigation Requests

• REQ_NEXT_FIELD Move to the next field
• REQ_PREV_FIELD Move to the previous field
• REQ_FIRST_FIELD Move to the first field.
• REQ_LAST_FIELD Move to the last field.
• REQ_SNEXT_FIELD Move to the sorted next field.
• REQ_SPREV_FIELD Move to the sorted previous field.
• REQ_SFIRST_FIELD Move to sorted first field.
• REQ_SLAST_FIELD Move to sorted last field.
• REQ_LEFT_FIELD Move left to field.
• REQ_RIGHT_FIELD Move right to field.
• REQ_UP_FIELD Move up one field.
• REQ_DOWN_FIELD Move down one field.

These requests treat fields as cyclic, moving off the end of the page will return you to the top.