[nigeltao]

Wuffs and SkWuffsCodec.cpp author here. Wuffs' GIF decoder has shipped in Google Chrome since July 2021 (milestone M93).

A fair chunk out of that 1000 lines of glue code is adapting Wuffs' API to Skia's API. (Skia is the 2-D graphics library used by Chromium and many other projects). Specifically, GIFs can be animated, Wuffs' animation API is designed for sequential access and its state needs O(1) memory but Skia's SkCodec animation API allows random access and needs O(N) memory, where N is the number of animation frames.

Random access means that, after decoding frame 100, the SkCodec can rewind and produce frame 70 (by scanning backwards through its O(N) state to find the most recent I-Frame equivalent that's <= 70 and replaying forward from there).

Random access seems a bit of a weird feature to me, but Chrome/Skia's old GIF codec could do it, for whatever historical reasons, so the new Wuffs-backed one does too (even though it needed a chunk of glue code).