Comment 8 for bug 248271

(In reply to comment #5)
> Windows only? I looked at APNG vs GIF in bug 394943, at the time I only saw
> perf issues on OS X (which has since been fixed).
>

This is a CPU issue, so it's different than what you saw in bug 394943.

--

Two things changed in the new throbber:
1) GIF -> APNG
2) Simple image -> Image with an alpha channel for anti-aliasing

If it's #1, then there might be a technical fix for this problem. But if it's #2, then there's really not much that could be done about this, as that represents the cost of anti-aliasing. Unfortunately, it looks like that the problem here is indeed #2. I just tested the throbber in bug 326817 comment 3 (an APNG version of the old GIF throbber), and its CPU consumption looked similar to that of the old throbber.

So I think there are three options, none of which are very pretty:
A) Get rid of the throbber anti-aliasing
B) Offer an option to the user (like an "I'm using an old machine" mode
   where throbber anti-aliasing and other expensive things are disabled)
C) Ignore this with the knowledge that as more of these old machines
   are retired, this will matter less