Hi @nabru, thanks for your feedback. Please be aware that calibration is something handled externally by the Tobii Core Software that runs in the system tray and cannot be called programatically by the new Core SDK. This is quite intentional so as to avoid external program overwriting system-wide calibration settings.
You can howeer launch an executable for a quick 3-point calibration from the command line (and hence integrate into a program if necessary).
Accordingly, from your description it does not seem that migrating your code would be of a benefit in this case. I understand you are using the older Gaze SDK as so are able to launch calibration directly? If you would care to share the project code on Github (or similar) we would be happy to take a look of course, but please bear in mind that the Core SDK does not support launching calibration directly from this API.
Custom calibration is possible via the Stream Engine API however this is c++ only at this time and would necessitate the purchase of a special custom calibration licence to do so.
Regarding head tracking, this is an additional metric exposed in the Core SDK for Windows so would be called much like any other variable (gaze location, eye location, etc) according to need.
Hopefully this clarifies the situation, please let us know any further information we can provide.