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5.6.3 Form data

Procedure: data-ahead? form
Procedure: data-behind? form

These procedures test if there is ahead or behind the current screen of the given form form. They return #t or #f.

This could be because a text entry has been declared to have variable size (not O_STATIC) and not all text from the entry is being displayed.

5.6.4 Command-processing loop of the form system

Constant: %is-form-driver-wide

This constant is #t if the form-driver function is capable of processing characters with representations that are greater than 8 bits.

Procedure: form-driver form c

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

The form driver requests are as follows:

REQ_NEXT_PAGEMove to the next page.
REQ_PREV_PAGEMove to the previous page.
REQ_FIRST_PAGEMove to the first page.
REQ_LAST_PAGEMove to the last field.
REQ_NEXT_FIELDMove to the next field.
REQ_PREV_FIELDMove to the previous field.
REQ_FIRST_FIELDMove to the first field.
REQ_LAST_FIELDMove to the last field.
REQ_SNEXT_FIELDMove to the sorted next field.
REQ_SPREV_FIELDMove to the sorted previous field.
REQ_SFIRST_FIELDMove to the sorted first field.
REQ_SLAST_FIELDMove to the sorted last field.
REQ_LEFT_FIELDMove left to a field.
REQ_RIGHT_FIELDMove right to a field.
REQ_UP_FIELDMove up to a field.
REQ_DOWN_FIELDMove down to a field.
REQ_NEXT_CHARMove to the next char.
REQ_PREV_CHARMove to the previous char.
REQ_NEXT_LINEMove to the next line.
REQ_PREV_LINEMove to the previous line.
REQ_NEXT_WORDMove to the next word.
REQ_PREV_WORDMove to the previous word.
REQ_BEG_FIELDMove to the beginning of the field.
REQ_END_FIELDMove to the end of the field.
REQ_BEG_LINEMove to the beginning of the line.
REQ_END_LINEMove to the end of the line.
REQ_LEFT_CHARMove left in the field.
REQ_RIGHT_CHARMove right in the field.
REQ_UP_CHARMove up in the field.
REQ_DOWN_CHARMove down in the field.
REQ_NEW_LINEInsert or overlay a newline.
REQ_INS_CHARInsert a blank at the cursor.
REQ_INS_LINEInsert a blank line at the cursor.
REQ_DEL_CHARDelete character at the cursor.
REQ_DEL_PREVDelete character before the cursor.
REQ_DEL_LINEDelete line at the cursor.
REQ_DEL_WORDDelete blank-delimited word at the cursor.
REQ_CLR_EOLClear to end of line from cursor.
REQ_CLR_EOFClear to end of field from cursor.
REQ_CLR_FIELDClear the entire field.
REQ_OVL_MODEEnter overlay mode.
REQ_INS_MODEEnter insert mode.
REQ_SCR_FLINEScroll the field forward a line.
REQ_SCR_BLINEScroll the field backward a line.
REQ_SCR_FPAGEScroll the field forward a page.
REQ_SCR_BPAGEScroll the field backward a page.
REQ_SCR_FHPAGEScroll the field forward half a page.
REQ_SCR_BHPAGEScroll the field backward half a page.
REQ_SCR_FCHARScroll the field forward a character.
REQ_SCR_BCHARScroll the field backward a character.
REQ_SCR_HFLINEHorizontal scroll the field forward a line.
REQ_SCR_HBLINEHorizontal scroll the field backward a line.
REQ_SCR_HFHALFHorizontal scroll the field forward half a line.
REQ_SCR_HBHALFHorizontal scroll the field backward half a line.
REQ_VALIDATIONValidate field.
REQ_NEXT_CHOICEDisplay next field choice.
REQ_PREV_CHOICEDisplay previous field choice.

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.

It is important to note that when characters are Unicode codepoints greater than U+00FF, the form driver will only use them for versions of the wide ncurses form library that are 2014 or newer. For older version of ncurses, only printable characters (which must be positive, less than 256) are allowed. The %is-form-driver-wide constant can be used to check if form-driver can handle characters whose numerical representations are greater than 256.

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:

If you click below the display region of the form:

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

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.

If the second argument is neither printable nor one of the above predefined 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.

form-driver returns one of the following error codes: E_OK if the routine succeeded, E_BAD_ARGUMENT if the routine detected an incorrect or out-of-range argument, E_BAD_STATE if the routine was called from an initialization or termination function, E_NOT_POSTED if the form has not been posted, E_INVALID_FIELD if the contents of field is invalid, E_REQUEST_DENIED if the form driver could not process the request, E_SYSTEM_ERROR if a system error occurred, and E_UNKNOWN_COMMAND if the form driver code saw an unknown request code.

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