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Questions tagged [covariance]

Covariance, contravariance and invariance describe how the existing type inheritance hierarchy changes when subjected to some transformation (such as usage within generics). If the transformation keeps the ordering of the original hierarchy, it is "covariant". If it reverses it, it is "contravariant". If it breaks it, it is "invariant".

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Imitate Qt Quick's QQuickFramebufferObject, but do the syncing more tidily (with covariance)

I'm making a system similar to Qt Quick with its scenegraph. Since it's embedded within Qt Quick with its threading system, the items' Renderers should sync some ...
Stefan Monov's user avatar