.\"***************************************************************************
-.\" Copyright (c) 1998-2010,2015 Free Software Foundation, Inc. *
+.\" Copyright (c) 1998-2015,2016 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" copy of this software and associated documentation files (the *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" $Id: form_driver.3x,v 1.25 2015/12/05 21:06:26 tom Exp $
+.\" $Id: form_driver.3x,v 1.26 2016/12/04 01:01:17 tom Exp $
.TH form_driver 3X ""
.de bP
.IP \(bu 4
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.
+.SS Field validation
+The form library makes updates to the window associated with form fields rather than
+directly to the field buffers.
+.PP
+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 \fBset_field_type\fP.
+.PP
+.PP
+You can validate a field without making any changes to it using
+\fBREQ_VALIDATION\fP.
+The form driver also validates a field in these cases:
+.bP
+a call to \fBset_current_field\fP attempts to move to a different field.
+.bP
+a call to \fBset_current_page\fP attempts to move to a different page of the form.
+.bP
+a request attempts to move to a different field.
+.bP
+a request attempts to move to a different page of the form.
+.PP
+In each case, the move fails if the field is invalid.
+.PP
+If the modified field is valid, the form driver copies the modified
+data from the window associated with the field
+to the field buffer.
.SS Mouse handling
.PP
If the second argument is the KEY_MOUSE special key, the associated
.SH SEE ALSO
\fBcurses\fR(3X),
\fBform\fR(3X),
+\fBform_field_buffer\fR(3X),
+\fBform_field_validation\fR(3X),
+\fBform_fieldtype\fR(3X),
\fBform_variables\fR(3X),
\fBgetch\fR(3X).
.SH NOTES