GtkViewport and gtk_widget_set_app_paintable()

["Ustun ERGENOGLU" <ustun ergenoglu gmail com>]

Hello folks,

I'm just trying to tell GtkViewport not draw the default background
with gtk_widget_set_app_paintable() function, and setting background
pixmap gdk_window_set_back_pixmap (vp->window, NULL, FALSE);

it still draws the gray background.

does anybody have a clue on how to do it?

thanks in advance