How to be notified before GdkWindow is destroyed

[Gustavo João Alves Marques Carneiro <ee96090 fe up pt>]

  I have a GtkDrawingArea widget on which I'm using an external library
(libplot) to draw directly to widget->window. I need to receive a
notification when the widget is about to be destroyed but *before* the
GdkWindow is destroyed, because libplot is still using the window.

  Which signal should I connect to? I already tried "destroy" and
"unrealize", but those happen too late---the window is already destroyed.
I also tried to keep a reference to the GdkWindow (with g_object_ref) to
prevent it from being destroyed, but it didn't work. Any idea will be
deeply appreciated.

-- 
Gustavo João Alves Marques Carneiro <ee96090 fe up pt>
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