Firefox doesn't play fullscreen in html5 videos

[jenny7]

If I press fullscreen on a html5 video on youtube (or any other site with html5 videos), no fullscreen mode is entered, but firefox doesn't react anymore or very very slow to mouse clicks.

This happens both for my intel as well as for my nvidia graphics.

I am using xmonad as window manager if this matters.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: firefox 45.0+build2-0ubuntu0.15.10.1
ProcVersionSignature: Ubuntu 4.2.0-34.39-generic 4.2.8-ckt4
Uname: Linux 4.2.0-34-generic x86_64
AddonCompatCheckDisabled: False
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/by-path', '/dev/snd/hwC0D0', '/dev/snd/pcmC0D0c', '/dev/snd/pcmC0D0p', '/dev/snd/controlC0', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
BuildID: 20160304114936
Channel: Unavailable
Date: Fri Mar 25 11:12:20 2016
Extensions: extensions.sqlite corrupt or missing
ForcedLayersAccel: False
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
IncompatibleExtensions: Unavailable (corrupt or non-existant compatibility.ini or extensions.sqlite)
InstallationDate: Installed on 2016-03-24 (1 days ago)
InstallationMedia: Lubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
IpRoute:
 default via 192.168.100.1 dev enp0s25 proto static metric 100
 192.168.100.0/24 dev enp0s25 proto kernel scope link src 192.168.100.51 metric 100
Locales: extensions.sqlite corrupt or missing
Plugins: Shockwave Flash - /usr/lib/flashplugin-installer/libflashplayer.so
PrefSources: prefs.js
Profiles: Profile0 (Default) - LastVersion=45.0/20160304114936 (In use)
RunningIncompatibleAddons: False
SourcePackage: firefox
Themes: extensions.sqlite corrupt or missing
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/18/2015
dmi.bios.vendor: LENOVO
dmi.bios.version: G5ETA3WW (2.63 )
dmi.board.asset.tag: Not Available
dmi.board.name: 2447KD9
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrG5ETA3WW(2.63):bd09/18/2015:svnLENOVO:pn2447KD9:pvrThinkPadW530:rvnLENOVO:rn2447KD9:rvrNotDefined:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 2447KD9
dmi.product.version: ThinkPad W530
dmi.sys.vendor: LENOVO

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Kjell L. (lkjell)]

Is it the same bug as this one? https://bugzilla.mozilla.org/show_bug.cgi?id=1273746

[madbiologist (me-again)]

According to the bug Kjell L linked (and another bug linked from that bug), this is a bug in xmonad.

[madbiologist (me-again)]

Official support for Ubuntu 15.10 "Wily Werewolf" has ended. If this issue is still occurring on Ubuntu 17.04 "Zesty Zapus" with xmonad, please run ubuntu-bug to file a new bug in xmonad so that we can get the correct and latest log files and system info.