I have seen an example of using the OnFocusEvent component to handle gaze, and how we can use the FocusEnter and FocusLost methods, as well as how to wire-up these functions in Unity…
But I wonder if this is just the old way of doing things or is it really different to using the common IFocusable interface and putting the code into its OnFocusEnter and OnFocusExit methods?
That’s specific to the HoloToolkit/MixedRealityToolkit, which wasn’t written by any Unity dev. You’d probably have better luck asking about that over here: GitHub - microsoft/MixedRealityToolkit-Unity: This repository is for the legacy Mixed Reality Toolkit (MRTK) v2. For the latest version of the MRTK please visit https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity
Sorry, my bad. I logged onto https://forum.unity3d.com/forums/hololens.102/ and then posted my question. Obviously, it did not actually log onto the link.