* restructure the widgets used to implement ElementBox
* inject a Gtk::EventBox top-level base type to capture all Gdk-Events
* push the Gtk::Frame one level down (TODO: API for managing children)
With these changes
* dragging of Clips in the timeline works as expected
* size constraints are observed precisely
* all warnings and assertion failures from GTK disappeared
Thus we can conclude that the solution approach for size constrained widgets
was successful and this challenging problem is solved.
Ichthyostega
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