Hope I am not asking a redundant question, I am a self taught coder so I don't know terms of art. I have looked on here and StackExchange to no avail, but maybe I'm just not structuring my search terms well.

For an iOS app in particular (will not run on desktops) I am trying to figure out how to determine what part of a larger page in a Scroll View a user has in front of them. I have to imagine this functionality exists, as Instagram and other social media apps seem to be able to track what a user actually sees.

Use case example: for a employee safety policy, make sure the text of a long safety document has been viewed gradually, and being able to track how long users looked at each section of text and report that back to the app.

Maybe I am doing a bad job of explaining this. Thank you!

(I try to ask good questions but get yelled at on StackExchange, so sorry in advance if I did this wrong or it's unclear. If I just don't know the right word to search that's all I need)

Thank you!