- default_height is -1 if unset, or >= 0 if
a default height is set
-GtkWindow::allow_grow, GtkWindow::resizable:
- - equivalent properties; changing one notifies on the other
+GtkWindow::resizable:
- if FALSE, we set the min size to the max size in the geometry
hints.
- If the app programmer has called gtk_window_set_geometry_hints()