Query about LazyOffsetArray16 iterator

[asibahi]

Hello.

This is not an issue. Just a question about the library. I am hoping @RazrFalcon would help.

As far as I understand the type and the library, the iterator for LazyOffsetArray16is not fused, and can be called multiple times even after the the first None. Yet the usages I have come across in rustybuzz don't do that.

My question is why the data is structured that way. Why is the inner array a LazyArray of optional offsets if the iterator is supposed at the first null found and that's it.

in other words why is the offsets array a LazyArray16(Option<Offset16>) and not LazyArray16(Offset16) ?

[RazrFalcon]

Hi! I wrote this code like 5-6 years ago, so I would not be able to provide much more info that already mentioned in the comments.

Reading the code I do see that it breaks the Rust Iterator convention. Not sure how bad it is. As long as the caller expects this - it's fine, but it should probably return Option<Option<Self::Item>>.
You can try fixing it. Not sure how much changed to rustybuzz it would require.

As for the TrueType itself, it does explicitly states that some offsets can be NULL/0:

Array of offsets to SequenceRuleSet tables, from beginning of SequenceContextFormat1 table (offsets may be NULL).