Currently I am working on a certain app for Apple platform and will add Apple Sign-in on it.
On the design requirement there are certain rules for when we made our custom button for it. One of it is: using Apple System Font.
So, then I search what is "Apple Sytem Font" and the found this: https://developer.apple.com/fonts/system-fonts/
From what I understand (cmiiw), is that Apple has sets of font listed there which I can choose from one of them and use it on my apps.
The problem in here is that my app use a some framework and tools for the UI, which need the fonts file to be available locally on the machine. Because it will be used to build the assets into the app data.
So, the question is how can I have the .ttf file from the those list?
They said to use Apple Font Book to download it, but I don't know how do I possibly get the .ttf file from it. From what I understand Apple Font Book is like Bitstream Font Navigator from Corel, no?
The iOS system font is San Francisco
https://developer.apple.com/fonts/
You should be able to download the variations from that link and install them on your "build the assets" system.