User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:23.0) Gecko/20130426 Firefox/23.0 Build ID: 20130426030834 Steps to reproduce: 1. Create fresh profile. 2. Go to http://upload.wikimedia.org/wikipedia/commons/2/29/Pacal_the_Great_tomb_lid.svg 3. Scroll vertically. Actual results: scrolling is not smooth . Nightly uses 100% CPU. Expected results: smooth scrolling. Profile :http://people.mozilla.com/~bgirard/cleopatra/#report=b57264d00d4ccf49ff09f0e1263d824aff8f9d5b
Confirmed in nightly 25 2013-07-31.
Still loads of unnecessary invalidation.
There's much less invalidation while scrolling nowadays. In fact when scrolling with the scrollbar there is no invalidation until I release the thumb. Similarly, when I two finger scroll a few pixels at a time, there isn't usually invalidation unless I lift my fingers off the trackpad for about half a second between each little bit of scrolling. Still, it would be better if we didn't invalidate stuff that is already on-screen at all.
These improvements are mostly from APZ and paint skipping, though. (Paint skipping means we don't build a display list if all that changed was the scroll position, and if that scroll position change did not affect size or location of the display port.) If you repeatedly move your mouse over and away from the scrollbar during scrolling, you still see lots of invalidations. Most of those are probably bug 1165185.