serde is really good, and really helpful. It's got us very far very quickly. But it has some significant frustrations, most notably the fact that it's not designed for random access.

Currently any structure that involves offsets (and now we're coming into handling layout, there are lots of them) requires a nasty process of reading the offset data, reading the rest of the structure, calculating how many bytes we've consumed so far in the structure, reading the rest of the available data into a vec, making a new slice starting of the available data from (offset - where we are), and passing that new slice to a separate deserializer. Serializing structs with offsets is even harder, and involves pulling together (possibly nested) serializations and computing their length, etc. The worse thing is that this all has to be done by hand for each structure. If we had true random access, most of the manual ser/de implementations would go away.

Realistically, we don't need the structure/data format abstraction that serde provides, as we are hardly likely to be serializing fonts to JSON or whatever. (I've tried it, it doesn't work...) So perhaps a custom ser/de would even be simpler.

Would be interested to hear opinions on this, particularly from @cmyr @raphlinus.