gtk+ use button to update Graph, code residing in callbacks.c

["S. Aguinaga" <sa_jr yahoo com>]

In interface.c I have some code for a graph and some basic set of X Y points for the plot.

I want to use a button to change the waveform.  The code of the button is in callbacks.c

But how do I reference the the correct GtkWidget?

The error messages when I click on the button are:

(harp_app_0:3806): GLib-GObject-WARNING **: invalid cast from `GtkDataboxLines' to `GtkDatabox'

** (harp_app_0:3806): CRITICAL **: gtk_databox_graph_add: assertion `GTK_IS_DATABOX (box)' failed

(harp_app_0:3806): GLib-GObject-WARNING **: invalid cast from `GtkDataboxLines' to `GtkDatabox'

** (harp_app_0:3806): CRITICAL **: gtk_databox_calculate_extrema: assertion `GTK_IS_DATABOX (box)' failed

This is what my callbacks.c file, here is my file:

#ifdef HAVE_CONFIG_H

#  include <config.h>

#endif

#include <gtk/gtk.h>

#include <math.h> 

#include "callbacks.h"

#include "interface.h"

#include "support.h"

void

button_clicked (GtkButton *synchioButton,

GtkWindow *parent)

{

//GtkWidget *dialog, *label, *image, *hbox;

GtkWidget *plotbox, *graph;

GdkColor color;

gfloat *X, *Y;

gint i;

g_print("SynchioButton I was clicked!\n");

X = g_new0 (gfloat, POINTS);   // WILL PROBABLY HAVE TO GET RID OF THIS 

Y = g_new0 (gfloat, POINTS); 

for (i = 1 ; i < POINTS + 1; i ++) { X [i] = i; Y [i] = log10 (i); } 

color.red   = 15535;

color.green = 15535;

color.blue  = 15535;  

graph = gtk_databox_lines_new (POINTS, X, Y, &color, 1); 

    gtk_databox_graph_add (GTK_DATABOX (plotbox), graph); 

gtk_databox_auto_rescale (GTK_DATABOX (plotbox), 0.05);

}