Active tab not shown, problem to reach Tab outside visible area in tab_bar




Tabbed Browser
5 years ago
5 years ago


(Reporter: Dalibor Toman, Unassigned)


15 Branch
Windows 7

Firefox Tracking Flags

(Not tracked)



(1 attachment)



5 years ago
Created attachment 676551 [details]

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:15.0) Gecko/20100101 Firefox/15.0.1
Build ID: 20120905151427

Steps to reproduce:

FF15.01 (but I observe the problem long time - i.e. much older versions of FF have it too). Windows 7, 64bit. I have windows taskbar on the left side of screen. I have 6 pinned tabs in FF. I open larger amount of tabs - to fill the whole tab bar.

Actual results:

next new tab often open as 'hidden' - it means there is not tab highlighted = you cannot see what tab belongs to current window/address bar. It is very annoying bug.

If I use < > buttons (via mouse) it is hard to move the tab bar. I must click several times to see any change. An then the tabs move not as I expected (just a part of the left/right tab shows etc so you canot see the x (close) sign on it for example)

Expected results:

1) the active tab should be clearly visible in the tab bar
2) whole active tab should be visible not only its left/right part


5 years ago
Component: Untriaged → Tabbed Browser

Comment 1

5 years ago
I've been having this for a long time on my macbook air, maybe since FF9 or so, maybe earlier. For a long time I didn't update from that early version because I strongly dislike your versioning scheme. When I finally did update from 9 to 15 or so, the bug was still present. An indicator that the versioning scheme is pretty broken, but that's besides the point.

I never once had it on my Debian box, despite thrashing it with 200+ tabs and months of uptime (congrats on stability, btw!). Because of this, I assumed that it was a mac toolkit related bug of some type. Recently, though, I got it again, this time on Debian AMD64 with only 20 or so tabs open (a VERY light workload). This firefox is 16.something and has been doing it today, hence finding this and adding my 2c. The only thing that this box and the mac have in common is 64 bit architecture. This box and the other Debian box that I NEVER have this problem with, are in all other ways near identical. Thus I strongly believe that it could be a variable type issue or similar.

I have one complaint to add, too. This person helpfully reported the same issue and was dismissed out of hand as having plugins  or look'n'feels activated causing it. Pretty rude and unconstructive IMO. Not the way to treat someone with legitimate feedback.

My resoponse to that helper is that I only have three plugins installed, and no extensions. Two of them are the same very stable dependable plugins I've been using for many many years:

Adblock plus

With the third being duckduckgo search bar.

IMO these are extremely unlikely to cause a core-gui rendering issue such as this.

As a dev with many years experience my gut-feel is that there is a problem with the code handling accounting of tab dimensions causing resulting math to be wrong, and the end tab, or part thereof, to not be shown.

When this happens there are other things that go along with it, as mentioned above. For example, double clicking the arrow no longer jumps a window-width of tabs.

So you've now got confirmed behaviour on all three major OSes from 3 different users across four different machines and 7+ versions. Please take this seriously and assign an experienced dev to deal with it.

Comment 2

5 years ago
I didn't mention, but I have three pinned tabs, always. If there's anything you need, testing wise, feel free to ask.

Comment 3

5 years ago
Hello! I'm back again. Firefox 10 (or is that 3.15?) was giving me some trouble burning CPU for no apparent reason, so I bit the bullet and upgraded to 20 and now, for the first time, I have this bug on 32bit Linux too. This is virgin downloaded untarred firefox, no Debian patches. So it's on all platforms. How this can remain "unconfirmed" is completely beyond me. Please acknowledge this bug! I'm not a big fan of Chrome, but when I have to kill 100+ tabs to restore normal functionality to my browser and kill it's up time in the process, I'm not a happy camper. Don't force me to switch. At least open a dialogue here so we can work toward solving the issue. Hell, give me some file names and a repository URL, I'll even have a look myself.
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