disconcerting URL bar effect: unstable font kerning

[Colin Watson]

Binary package hint: firefox-3.0

I recently started trying out firefox-3.0, and noticed a strange effect in the URL bar from time to time. It looks like kerning is calculated slightly differently when the URL bar is highlighted from when it isn't. Specifically, when there's a capital T in the URL bar (possibly happens with other letters too, but that's what I noticed most recently), the horizontal space allocated for the T is wider when highlighted than when not.

I've attached a small animation (created using byzanz) of what happens when I press Ctrl-L to highlight the URL, followed by right-arrow to unhighlight it, followed by Enter. You can see that when I press Enter there's a rather disconcerting effect where it recalculates the kerning and the last few characters of the URL "slide" back to their previous position. In fact, if you step through the animation frame by frame in the Gimp, you'll see in frames 5 through 7 that it actually animates this transition so that both the old and the new kerning are briefly visible. I'm sure this transition is useful in some other setting, but in this case it's remarkably ugly.

Although I have a number of extra font packages installed for development purposes, I believe I'm using Ubuntu 7.10's default fonts to all intents and purposes.

[Fabien Tassin (fta)]

I'm assuming you're running Firefox 3.0 Alpha 8 from Gutsy.
It seems you're experiencing Mozilla Bug #386759: https://bugzilla.mozilla.org/show_bug.cgi?id=386759
(could you confirm ?)

If it is indeed that bug, it has been fixed between Alpha 8 and Beta 1 (soon to enter Hardy, waiting sponsor/review).
I'm running a post Beta 1 build, and I can't reproduce it, while I clearly remember a kerning issue at the "dots" of some URLs or at the final "..." of URLs longer than the URL bar during the last few Alphas.

[Colin Watson (cjwatson)]

I'm running a mostly-7.10 system selectively upgraded to hardy, and you're quite right that I was running 7.10's firefox-3.0. After upgrading firefox-3.0 to the version in hardy (3.0~b1~rc3+nobinonly-0ubuntu1), I can no longer reproduce this bug. Thanks!