688235 - Make decoders not have callbacks

Status: NEW

(Core :: Graphics: ImageLib, defect)

Description

[Jeff Muizelaar [:jrmuizel]]

Having callbacks has a number of disadvantages:
 - The decoder can accidentally kill itself because the callback can kill the decoder. This forces us to reference count decoders
 - It makes it harder to nest decoders as needed by the ICO craziness

Getting rid of callbacks is hard though:
 - We currently need to communicate quite a bit of information out of the decoder
 - The information isn't of fixed size (multiple frames per write call)

We might be able to do it by checking for information after a Write call and having Write calls return after decoding a frame even if there's more data left.