Some of you may have noticed that the Firefox 3 nightly builds have felt a lot snappier since a few weeks ago. There’s an interesting story in that, one that I finally have time to write up. We’ve had a number of bugs on the Mac where people were complaining of bad performance compared to Firefox 2, usually involving a test where a page was scrolled by a small step 100 or so times, and the time from start to finish was recorded. In many of these tests, Fx3 was coming in at 50% to 500%+ slower. This was odd, because in theory the graphics layer (which is what scrolling is mostly exercising) in Firefox 3 should be faster, given that it’s talking almost directly to Quartz.
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Slashdot seems to have picked up on this, and in typical style, has completely misunderstood the post. To be clear, I do not think that Apple is in any way trying to purposely “cripple” non-Apple software. I also do not think that undocumented APIs give Safari any kind of “significant performance advantage” (as Firefox 3 should show!). However, as I said, the undocumented functionality could be useful for Firefox and other apps to implement things in an simpler (and potentially more efficient) manner. I don’t think this is malicious, it’s just an unfortunate cutting of corners that is way too easy for a company that’s not fully open to do.(link)

