The `mitkDisplayInteractor` has been replaced by the `mitkDisplayActionEventBroadcast` here: 251e40159685
The `mitkDisplayInteractor` is not required or used anymore, but some references still exist. This is because classes need to check for the `InteractionEventObserver` and see if this is of type `mitkDisplayInteractor` (`mitkDisplayActionEventBroadcast`) (e.g. see here: https://phabricator.mitk.org/source/mitk/browse/develop/Modules/Segmentation/Interactions/mitkTool.cpp$150-169).
Attention: `QtFreeRender` seems to create a `mitkDisplayInteractor` so we need to check if we can replace it here.
However, `InteractionEventObserver` should never be of type `mitkDisplayInteractor`, since this class is not used anymore.
Using this class would look something like this (example for `mitkDisplayActionEventBroadcast`): https://phabricator.mitk.org/source/mitk/browse/develop/Modules/QtWidgets/src/QmitkAbstractMultiWidget.cpp$49-53