+++ This bug was initially created as a clone of Bug #945161 +++ Even image.mem.decodeondraw is true we sometimes still decode the full image when all data is available. It happens when the image is in cache and downloads very fast.

What causes the full decode?

(In reply to Timothy Nikkel (:tn) from comment #1) > What causes the full decode? I'm not sure. I could be wrong. There seems so many way to trigger decode but some look suspicious. For example this one: http://hg.mozilla.org/mozilla-central/file/46041cc216fd/image/src/RasterImage.cpp#l1663 And this one: http://hg.mozilla.org/mozilla-central/file/46041cc216fd/image/src/RasterImage.cpp#l1739 For bug 945161 we want to get the layout information before we fully decode the image. But sometimes I couldn't get the frame size before we start decoding.

Moving to p3 because no activity for at least 1 year(s). See https://github.com/mozilla/bug-handling/blob/master/policy/triage-bugzilla.md#how-do-you-triage for more information