this is going on my nerves: i don't know how to fix these errors

(sbcl:3669): Gtk-CRITICAL **: gtk_cairo_transform_to_window: assertion 'GDK_IS_WINDOW (window)' failed

(sbcl:3669): Gdk-CRITICAL **: gdk_window_get_height: assertion 'GDK_IS_WINDOW (window)' failed

(sbcl:3669): Gdk-CRITICAL **: gdk_window_get_width: assertion 'GDK_IS_WINDOW (window)' failed

(sbcl:3669): Gtk-CRITICAL **: gtk_cairo_transform_to_window: assertion 'GDK_IS_WINDOW (window)' failed

(sbcl:3669): Gdk-CRITICAL **: gdk_window_get_height: assertion 'GDK_IS_WINDOW (window)' failed
fixed the code again. check buttons now control visibility of pictures in the canvas
add a new vbox so that i have one for the parameter settings and one for the check buttons that select which images are to be displayed
access values of spinbuttons