driver(3FORM)

💅 driver(3FORM) — bestie edition ✨

okay so you want to talk to the form system?? say less. this is form_driver and form_driver_w, straight out of the ncurses library-calls corner of the manual, and they are literally the command-processing loop of the whole form situation. you funnel your input events in here and the form does stuff. periodt.

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🌸 SYNOPSIS 🌸

#include <form.h>

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

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✨ DESCRIPTION ✨

💖 form_driver

so the vibe is: once a form has been posted (aka displayed), you should funnel input events into it through form_driver. this routine has three major input cases, and yes we're listing all three:

• The input is a form navigation request. Navigation request codes are constants defined in form.h, and they are distinct from the key- and character codes that wgetch(3NCURSES) hands back. different species, no cap.
• The input is a printable character. Printable characters (which must be positive and less than 256) get checked according to the program's locale settings.
• The input is the KEY_MOUSE special key, which is attached to a mouse event. 🐭

🦋 form_driver_w

this one's an extension and it simplifies using the forms library with wide characters. the input is either a key code (a request) or a wide character returned by get_wch(3NCURSES). you also gotta pass the type along, so the library can figure out whether that parameter is a wide character or a request. iykyk.

👑 Form Driver Requests

here's the whole request roster, bestie. every single one. no skips.

• 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 ½ 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 ½ page.
• REQ_SCR_FLINE — Scroll field forward 1 line.
• REQ_SCR_FPAGE — Scroll field forward 1 page.
• REQ_SCR_HBHALF — Horizontal scroll field backward ½ line.
• REQ_SCR_HBLINE — Horizontal scroll field backward 1 line.
• REQ_SCR_HFHALF — Horizontal scroll field forward ½ 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.

(and yes, REQ_NEXT_PAGE really is listed twice up there. that's the original's business, not mine. 🫶)

so: if the second argument is a printable character, the driver places it in the current position in the current field. if it's one of the forms requests listed above, that request gets executed. simple as.

🌈 Field Validation

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

the form driver gives you low-level control over updates to the form fields. it also provides for validating modified fields, to make sure the contents meet whatever constraints an application may attach using set_field_type.

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

• a call to set_current_field attempts to move to a different field.
• a call to set_current_page attempts to move to a different page of the form.
• a request attempts to move to a different field.
• 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 over to the field buffer. slay.

🐭 Mouse Handling

if the second argument is the KEY_MOUSE special key, the associated mouse event gets translated into one of the above pre-defined requests. currently only clicks in the user window (like, 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:

• the form cursor is positioned to that field.
• 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.
• 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's an application-specific command and returns E_UNKNOWN_COMMAND. application-defined commands should be defined relative to MAX_COMMAND, which is the maximum value of these pre-defined requests. write that down.

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⭐ 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.

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🌍 PORTABILITY 🌍

these routines emulate the System V forms library. they were not supported on Version 7 or BSD versions. ok so.

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💜 AUTHORS 💜

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

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🔥 SEE ALSO 🔥

ncurses(3NCURSES), form(3FORM), fieldtype(3FORM), field_buffer(3FORM), field_validation(3FORM), form_variables(3FORM), getch(3NCURSES)

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and that's the whole page bestie!! 💖 this lil masterpiece comes to you courtesy of ncurses 6.6, dated 2025-10-04, and it's the driver(3FORM) page. go forth and funnel those input events. mwah 🫶✨