[seltzered_]

This. If you ever look at apples raw input touch privateframework it provides enough data for the relative direction/size as well as has some encoded states to at least detect between a very faint touch and a finger on the trackpad.

This I think goes back to the first unibody MacBooks from around 2008.

[wtallis]

The multitouch trackpads actually showed up in the early 2008 MacBook Pros that were the last ones before switching to the unibody enclosure (IIRC the keyboard/trackpad parts could be retrofitted into 2007 MacBook Pros). The early 2008 models still had a separate physical button at the bottom of the trackpad. The late 2008 models got rid of the button and made the whole trackpad hinged at the top to act as a button. Then in 2015 they introduced the Force Touch trackpad that fixed the awkwardness of needing more force to click the further up the trackpad you went.

[seltzered_]

Yep. And this blog post from 2009 was a big inspiration for me in exploring touch on the mac: https://archive.org/details/2009-03-28-steike-code-macbook-m...

and a comment a few years ago by me: https://news.ycombinator.com/item?id=23274577