(inkscape:599): Gtk-WARNING **: Attempting to add a widget with type
gtkmm__GtkHBox to a gtkmm__GtkDialog, but as a GtkBin subclass a
gtkmm__GtkDialog can only contain one widget at a time; it already
contains a widget of type GtkVBox
and the dialog is empty, tiny sized, not modal, and jumps up in the
corner of the screen...