From my understanding - it is proprietary at the moment but Apple has publicly pushed for other vendors to do something similar and for it to be standardized. T

From my understanding - it is proprietary at the moment but Apple has publicly pushed for other vendors to do something similar and for it to be standardized. There is a discussion on w3c to make this a standard: https://lists.w3.org/Archives/Public/www-style/2015Jul/0169.html https://lists.w3.org/Archives/Public/www-style/2015Jul/0169....