This affects fennec and b2g, but is more easily reproduceable on the latter (likely down to lower-spec hardware). STR: 1. Log on to twitter or Facebook (or any relatively complex site that scrolls a reasonable distance). 2. Scroll down a bit, fast enough that you get to see low precision tiles briefly 3. Select a tweet/post 4. Go back Expected: The previous page is shown in full resolution Actual: The previous page is shown in low precision, before shortly after being re-rendered in full resolution. The low precision tiles are only transient, so this isn't the worst thing in the world, but it is noticeable and can be especially confusing when the tiles have gone stale. This manifests more rarely, but worse in other situations, where you see content that is completely incorrect (such as on the mobile BBC News site). I think I've brought this up before, but I do think this is a bug in the low precision tiles coherency code - you should never see low precision tiles when you aren't scrolling. It could well be that they need to be invalidated at some point where they aren't, or that the valid region isn't being synchronised correctly at some point. Cc'ing kats and botond, as this code was mostly rewritten by them during the great units refactor of 2013.

Adding snorp as I think he was assigned the bbc bug (bug 1061268)

Also adding :rbarker, as he's touched this code and I feel should share this pain :)

Not much I can do without reproducible STR right now. I'll keep an eye out for it though - I have seen this occasionally on Fennec but not enough to nail it down. (In reply to Chris Lord [:cwiiis] from comment #0) > Cc'ing kats and botond, as this code was mostly rewritten by them during the > great units refactor of 2013. We didn't really touch the tile-coherency code so much. At least I didn't.