I've been running Firefox nightly and everything is going swimmingly except for nightly's conception of "full screen". When I watch, for example, a video from Youtube and switch to full screen mode, it's not really full screen. There is a bar on top showing all my tabs and below that is another bar containing the navigation bar and the search bar to its right. In the old days, full screen meant full screen: just the video with nothing above it. What's up? and how can I get back to true full-screen mode on nightly?
jdk

I'm afraid I can't reproduce your problem. I'm on Nightly updated yesterday 34.0a1 (2014-08-21) with the latest Flash for Linux 11.2.202.400 and, if it matters, an NVIDIA GT 640 with drivers 340.32. Hopefully the next update or the one after will fix it for you.

Thanks 273. Since it's Nightly I get updates every day (or more exactly, every night). Here's a screenshot showing what the problem is. It's been like this for over a week but one can always hope...
jdk

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Does it happen with all video, including HTML5, or just Flash video? If it's the latter which version of Flash are you running?

Yes, it does. I tried it with this one: https://www.youtube.com/watch?v=eIho2S0ZahI
As you can see it's an HTML5 video and exactly the same problem.
jdk

I'd be tempted to rename your profile and see whether that resolves it -- espscially if you have any plugins associated with the UI layout. I know now and again I have had to start with a fresh profile in Nightly, as annoying as that is.

AFAIK I have absolutely no plugins involving the UI. Most of my plugins involve security (mine) and ad blocking, etc. Never had this problem in the past so I thought maybe it was a feature. In any event I'll contact the Mozilla people and see if they have any answers. Thanks for the help.
jdk

I just created a new profile called "Test" with no add-ons at all. I tried a youtube video and switched to full-screen and it was back to normal. Obviously one of my plug-ins is the problem as you suggested above. What I'll do is disable them one-by-one until I find the guilty party. I'll inform Mozilla about this possible bug. After all I am using nightly. I expect these sorts of things.
Thanks again for the help.
jdk

No problem, glad to be able to help.
As a fellow nightly user I feel your pain -- as I mentioned similar things have happened to me in the past.

It gets more and more weird. I disabled all the extensions that might be involved in this issue: the Adblocks, DoNotTrackMe, httpsEverywhere but it's none of them. I have a bunch of dictionary extensions but I can't see them being a problem. That leaves things like ProfileSwitcher, Test Pilot, Toggle Persona, UserAgent Switcher and WOT. It's hard to imagine that any of those are involved but I'll disable them all and see if that makes any difference.
jdk
udate: nope. I disabled all those extensions listed above and no change.

Could it be your GUI preferences then? I know, dor example, I generally have classic menus enabled.

If that's the case then why would it be sensitive to which profile I'm using? Gui preferences don't change with the change of profiles. Also, I used Iceweasel up to version 31 and didn't have the full-screen problem. Whatever is causing it involves a change that took place between v. 31 and v.34.0a1. I haven't changed my GUI preferences in that interval and I've always used the GUI preferences as they came.

In any event, I posted the question on the Firefox support forum. We'll see what they come up with.
jdk