- 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.
+ 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.
+
+
+</PRE><H3><a name="h3-Field-validation">Field validation</a></H3><PRE>
+ 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 <STRONG>set_field_type</STRONG>.
+
+ You can validate a field without making any changes to it using
+ <STRONG>REQ_VALIDATION</STRONG>. The form driver also validates a field in these cases:
+
+ <STRONG>o</STRONG> a call to <STRONG>set_current_field</STRONG> attempts to move to a different field.
+
+ <STRONG>o</STRONG> a call to <STRONG>set_current_page</STRONG> attempts to move to a different page of
+ the form.
+
+ <STRONG>o</STRONG> a request attempts to move to a different field.
+
+ <STRONG>o</STRONG> 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.