See https://plus.google.com/108936502671219351445/posts/NkebPxeUGEx

I can reproduce this on Windows 7 as well.

The border of the URL bar is being changed on hover, which (I believe) is causing it to repaint. This is also true on m-c Nightly. The overpainting going on near the location panel anchor is a little distressing. That's not present on m-c Nightly.

Marking as P5 until we know that fixing this will help us in a significant way on the benchmarks that we are tracking.

I don't see this anymore on Mac. mconley, can you test win7 again? (I did file bug 946013 for the other issue described in comment 2)

Yep, still seeing this on Windows 7.

Is the theory in comment 2 correct? (I don't have a windows machine handy) If so, why do we only have a border effect on Windows?

Is this hover effect actually intentional or just a regression/bug/fallout from bug 755598?

It's not a regression from bug 755598, it's existed since we implemented the conditional forward button. It happens on Windows for two reasons: 1, we have a border-on-hover effect on windows for toolbarbuttons, and 2, parts of the toolbar item theme are not opaque due to lwthemes.

(In reply to Jared Wein [:jaws] (Away 20 Dec to 2 Jan) from comment #8) > It's not a regression from bug 755598, it's existed since we implemented the > conditional forward button. > > It happens on Windows for two reasons: 1, we have a border-on-hover effect > on windows for toolbarbuttons, and 2, parts of the toolbar item theme are > not opaque due to lwthemes. But on pre-australis the hover effect was limited to hovering the back/fwd-button. Now it appears when hovering the navbar. However, I thought that was the same cross-OS (certainly the same happened on OS X when I created the patches for this problem in bug 700363), and so I inferred that the points comment #7 and comment #2 made were about a different hover on the actual, entire URL bar, on Windows, rather than the toolbarbutton's hover showing through. That's also what the video from comment #0 seemed to be about, although maybe we're invalidating the entire urlbar frame because it is translucent and we're changing stuff underneath it and that's what you're saying. Maybe I misunderstood the aforementioned comments? I can't test this myself right now because my Windows machine is in a box in a truck 'somewhere'. :-\

(In reply to :Gavin Sharp (email gavin@gavinsharp.com) from comment #6) > Is the theory in comment 2 correct? (I don't have a windows machine handy) Yes. > If so, why do we only have a border effect on Windows? Because that sort of hover effect is native on Windows but not on other platforms.

Sounds like this is WONTFIX, then, unless we want to get rid of the hover effect. Seems to me that the benefits are greater than the costs; feel free to REOPEN if you disagree.