#include <gtk/gtk.h>
#include <cairo/cairo.h>

static cairo_surface_t *_create_gradient_surface(int width, int height)
{
  cairo_surface_t *resultant_surface = NULL;
  cairo_t *temp_cr;

  resultant_surface = cairo_image_surface_create(CAIRO_FORMAT_RGB24, width, height);
  temp_cr = cairo_create(resultant_surface);
  cairo_rectangle(temp_cr, 0, 0, width, height);
  cairo_set_source_rgb(temp_cr, 0, 0, 0);
  cairo_paint(temp_cr);
  cairo_destroy(temp_cr);

  return resultant_surface;

}


static gboolean
expose_event_callback (GtkWidget *widget, GdkEventExpose *event, gpointer data)
{
  cairo_surface_t *tmp = _create_gradient_surface(widget->allocation.width, widget->allocation.height);

  cairo_t *cr = gdk_cairo_create (widget->window);
  cairo_set_source_surface (cr, tmp, 0, 0);
  cairo_paint(cr);

  cairo_destroy(cr);
  cairo_surface_destroy(tmp);
  return TRUE;
}

int main(int argc, char **argv)
{
    /* GtkWidget is the storage type for widgets */
    GtkWidget *window;
    GtkWidget *button;
    
    gtk_init (&argc, &argv);
    
    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    g_signal_connect (window, "delete-event",
		      G_CALLBACK (gtk_main_quit), NULL);
    g_signal_connect (window, "destroy",
		      G_CALLBACK (gtk_main_quit), NULL);
    
    
    button = gtk_drawing_area_new();
    g_signal_connect (G_OBJECT (button), "expose_event",
                    G_CALLBACK (expose_event_callback), NULL);
    
    gtk_container_add (GTK_CONTAINER (window), button);
    gtk_widget_show (button);
    gtk_widget_show (window);
    gtk_main ();
    
    return 0;
}