# form_driver 3x 2025-10-04 ncurses 6.6 Library calls

    form_driver(3x)                  Library calls                 form_driver(3x)

## NAME

           form_driver, form_driver_w - command-processing loop of the form system

## SYNOPSIS

           #include <form.h>

           int form_driver(FORM *form, int c);
           int form_driver_w(FORM *form, int c, wchar_t wc);

## DESCRIPTION

### form_driver

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

           o   The  input  is a form navigation request.  Navigation request codes
               are constants defined in form.h, which are distinct from  the  key-
               and character codes returned by wgetch(3x).

           o   The  input  is  a printable character.  Printable characters (which
               must be positive, less than  256)  are  checked  according  to  the
               program's locale settings.

           o   The  input  is  the  KEY_MOUSE special key associated with an mouse
               event.

### form_driver_w

           This extension simplifies the use  of  the  forms  library  using  wide
           characters.   The  input  is  either  a  key code (a request) or a wide
           character returned by get_wch(3x).  The type must be passed as well, to
           enable the library  to  determine  whether  the  parameter  is  a  wide
           character or a request.

### Form Driver Requests

           The form driver requests are as follows:

           Name               Description
           ------------------------------------------------------------------------
           REQ_BEG_FIELD      Move to beginning of field.
           REQ_BEG_LINE       Move to beginning of the line.
           REQ_CLR_EOF        Clear to end of field from cursor.
           REQ_CLR_EOL        Clear to end of line from cursor.
           REQ_CLR_FIELD      Clear the entire field.
           REQ_DEL_CHAR       Delete character at the cursor.
           REQ_DEL_LINE       Delete line at the cursor.
           REQ_DEL_PREV       Delete character before the cursor.
           REQ_DEL_WORD       Delete blank-delimited word at cursor.
           REQ_DOWN_CHAR      Move down in field.
           REQ_DOWN_FIELD     Move down to a field.
           REQ_END_FIELD      Move to the end of field.
           REQ_END_LINE       Move to the end of the line.
           REQ_FIRST_FIELD    Move to the first field.
           REQ_FIRST_PAGE     Move to the first page.
           REQ_INS_CHAR       Insert a blank at the cursor.
           REQ_INS_LINE       Insert a blank line at the cursor.
           REQ_INS_MODE       Enter insert mode.
           REQ_LAST_FIELD     Move to the last field.
           REQ_LAST_PAGE      Move to the last field.
           REQ_LEFT_CHAR      Move left in field.
           REQ_LEFT_FIELD     Move left to a field.
           REQ_NEW_LINE       Insert or overlay a new line.
           REQ_NEXT_CHAR      Move to the next char.
           REQ_NEXT_CHOICE    Display next field choice.
           REQ_NEXT_FIELD     Move to the next field.
           REQ_NEXT_LINE      Move to the next line.
           REQ_NEXT_PAGE      Move to the next page.
           REQ_NEXT_PAGE      Move to the next page.
           REQ_NEXT_WORD      Move to the next word.
           REQ_OVL_MODE       Enter overlay mode.
           REQ_PREV_CHAR      Move to the previous char.
           REQ_PREV_CHOICE    Display previous field choice.
           REQ_PREV_FIELD     Move to the previous field.
           REQ_PREV_LINE      Move to the previous line.
           REQ_PREV_PAGE      Move to the previous page.
           REQ_PREV_WORD      Move to the previous word.
           REQ_RIGHT_CHAR     Move right in field.
           REQ_RIGHT_FIELD    Move right to a field.
           REQ_SCR_BCHAR      Scroll field backward 1 character.
           REQ_SCR_BHPAGE     Scroll field backward 1/2 page.
           REQ_SCR_BLINE      Scroll field backward 1 line.
           REQ_SCR_BPAGE      Scroll field backward 1 page.
           REQ_SCR_FCHAR      Scroll field forward 1 character.
           REQ_SCR_FHPAGE     Scroll field forward 1/2 page.
           REQ_SCR_FLINE      Scroll field forward 1 line.
           REQ_SCR_FPAGE      Scroll field forward 1 page.
           REQ_SCR_HBHALF     Horizontal scroll field backward 1/2 line.
           REQ_SCR_HBLINE     Horizontal scroll field backward 1 line.
           REQ_SCR_HFHALF     Horizontal scroll field forward 1/2 line.
           REQ_SCR_HFLINE     Horizontal scroll field forward 1 line.
           REQ_SFIRST_FIELD   Move to the sorted first field.
           REQ_SLAST_FIELD    Move to the sorted last field.
           REQ_SNEXT_FIELD    Move to the sorted next field.
           REQ_SPREV_FIELD    Move to the sorted previous field.
           REQ_UP_CHAR        Move up in field.
           REQ_UP_FIELD       Move up to a field.
           REQ_VALIDATION     Validate field.

           If  the  second argument is a printable character, the driver places it
           in the current position in the current field.  If  it  is  one  of  the
           forms requests listed above, that request is executed.

### Field Validation

           The  form  library  makes  updates  to  the window associated with form
           fields rather than directly to the field buffers.

           The form driver provides low-level control over  updates  to  the  form
           fields.   The  form driver also provides for validating modified fields
           to ensure that the contents meet whatever  constraints  an  application
           may attach using set_field_type.

           You  can  validate  a  field  without  making  any  changes to it using
           REQ_VALIDATION.  The form driver also validates a field in these cases:

           o   a call to set_current_field attempts to move to a different field.

           o   a call to set_current_page attempts to move to a different page  of
               the form.

           o   a request attempts to move to a different field.

           o   a request attempts to move to a different page of the form.

           In each case, the move fails if the field is invalid.

           If  the  modified  field  is valid, the form driver copies the modified
           data from the window associated with the field to the field buffer.

### Mouse Handling

           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 form display
           area or the decoration window) are handled.

           If you click above the display region of the form:

              a REQ_PREV_FIELD is generated for a single click,

              a REQ_PREV_PAGE is generated for a double-click and

              a REQ_FIRST_FIELD is generated for a triple-click.

           If you click below the display region of the form:

              a REQ_NEXT_FIELD is generated for a single click,

              a REQ_NEXT_PAGE is generated for a double-click and

              a REQ_LAST_FIELD is generated for a triple-click.

           If you click at an field inside the display area of the form:

              o   the form cursor is positioned to that field.

              o   If you double-click a field, the form cursor  is  positioned  to
                  that field and E_UNKNOWN_COMMAND is returned.  This return value
                  makes sense, because a double click usually means that an field-
                  specific  action  should be returned.  It is exactly the purpose
                  of this return value to  signal  that  an  application  specific
                  command should be executed.

              o   If  a  translation  into a request was done, form_driver returns
                  the result of this request.

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

### Application-defined Commands

           If  the  second argument is neither printable nor one of the above pre-
           defined form requests, the driver assumes it is an application-specific
           command and returns  E_UNKNOWN_COMMAND.   Application-defined  commands
           should  be  defined relative to MAX_COMMAND, the maximum value of these
           pre-defined requests.

## RETURN VALUE

           form_driver returns one of the following error codes:

           E_OK The routine succeeded.

           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 form has not been posted.

           E_INVALID_FIELD
                Contents of field is invalid.

           E_NOT_CONNECTED
                No fields are connected to the form.

           E_REQUEST_DENIED
                The form driver could not process the request.

           E_SYSTEM_ERROR
                System error occurred (see errno(3)).

           E_UNKNOWN_COMMAND
                The form driver code saw an unknown request code.

## PORTABILITY

           These routines emulate the System  V  forms  library.   They  were  not
           supported on Version 7 or BSD versions.

## AUTHORS

           Juergen Pfeifer.  Manual pages and adaptation for new curses by Eric S.
           Raymond.

## SEE ALSO

           curses(3x),    form(3x),   form_fieldtype(3x),   form_field_buffer(3x),
           form_field_validation(3x), form_variables(3x), getch(3x)

    ncurses 6.6                       2025-10-04                   form_driver(3x)