FileSelectionDialog is not necessary in most cases because the Motif toolkit provides FileSelectionDialog resources
that access most of the important resources of the children. You should only get handles to the children if you need to
change resources that are not involved in the file selection mechanisms.
7.5.3 Callback Routines
The XmNokCallback, XmNcancelCallback, XmNapplyCallback, XmNhelpCallback, and
XmNnoMatchCallback callbacks can be specified for a FileSelectionDialog as they are for SelectionDialog. The
callback routines take the usual parameters, but the callback structure passed in the call_data parameter is of type
XmFileSelectionBoxCallbackStruct. The structure is declared as follows:
typedef struct {
int reason;
XEvent *event;
XmString value;
int length;
XmString mask;
int mask_length;
XmString dir;
int dir_length;
XmString pattern;
int pattern_length;
} XmFileSelectionBoxCallbackStruct;
The value of the reason field is an integer value that specifies the reason that the callback routine was invoked. The
possible values are the same as those for a SelectionDialog:
XmCR_OK
XmCR_APPLY
XmCR_CANCEL
XmCR_HELP
XmCR_NO_MATCH
The value field contains the item that the user selected from the files list or typed into the selection text entry area.
The value corresponds to the XmNdirSpec resource and it does not necessarily have to match an item in the
directories or files lists. The mask field corresponds to the XmNdirMask resource; it represents a combination of the
entire pathname ...