set the directory, change the directory or get the file mask to work.

Answer: The 1.0 File Selection Box is broken, and these don't work.  They
weren't fixed until Motif 1.04.  Use these later versions of 1.0 or switch to
Motif 1.1 where it changed a lot.

Joe Hildebrand has a work-around for some of this: Before popping up an
XmFileSelectionDialog, change to the directory you want.  When a file is
selected, check if it is a directory, so that we can change to it.  i.e.

static void show_file_box_CB(w, client_data, call_data)
Widget               w;
Widget               client_data;
XmAnyCallbackStruct  *call_data;
{
chdir("/users/hildjj/files");
XtManageChild(client_data);
}

static void val_save(w, client_data, call_data)
Widget       w;
Widget       client_data;
XmSelectionBoxCallbackStruct *call_data;
{
struct stat buf;  /* struct stat is defined in stat.h */
char *filename;

/* get the file name from the FileSelectionBox */
filename = SmX(call_data->value);

/* get the status of the file named filename, and put it into buf */
if (!stat(filename, &buf))
{
/* if it's a directory */
/* if it's a directory */
if(S_ISDIR(buf.st_mode))
{
 /* change to that directory, and update the FileSelectionBox */
chdir(filename);
XmFileSelectionDoSearch(w, NULL);
}
else
 /* if it's a regular file */
 if(S_ISREG(buf.st_mode))
    /* ask if it should be overwritten */
    XtManageChild(valbox);
 else
    /* it's another kind of file.  What type, i can't think of,
       but it might happen */
    pop_up_error_box(client_data, "Error saving file");
}
else  /* we couldn't get the file status */
{
/* if it's because the file doesn't exist, we're golden */
if (errno == ENOENT)
 save_file();
else   /* there is some other problem getting the status.
        e.g. bad path */
 pop_up_error_box(client_data, "Error saving file");
}
}

this still doesn't implement the file masking stuff.