Why some Fn keys (like PowerOff) are un-mappable (and how to map them anyway)?

[Adam Ryczkowski]

There are keys, that gets captured by the `xev` or `acpi_listen` and which does produce a valid entry in keyboard-mapping settings gui when user is asked to press it for new accelerator key, but the action is not triggered by pressing them afterwards.

The most irritating example is the `PowerOff` key, but I can list other, un-named Fn+... keys.

Since the GUI was able to read the key-press event, why the Ubuntu cannot actually make this key to trigger an event?

I did disable Ubuntu's own PowerOff handler with `gsettings set org.gnome.settings-daemon.plugins.power button-power "nothing"`.

How to map the PowerOff key?

Actually, I need to map the PowerOff key into the End key, but I guess being able to map it to *anything* is a first step .

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: xorg 1:7.7+1ubuntu8.1
ProcVersionSignature: Ubuntu 3.13.0-45.74-generic 3.13.11-ckt13
Uname: Linux 3.13.0-45-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.14.1-0ubuntu3.6
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity
Date: Tue Feb 3 15:23:58 2015
DistUpgraded: Fresh install
DistroCodename: trusty
DistroVariant: ubuntu
EcryptfsInUse: Yes
ExtraDebuggingInterest: Yes
GraphicsCard:
 Intel Corporation 4th Gen Core Processor Integrated Graphics Controller [8086:0416] (rev 06) (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. Device [1043:185d]
InstallationDate: Installed on 2014-04-04 (304 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Daily amd64 (20140404)
MachineType: ASUSTeK COMPUTER INC. G551JM
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-45-generic root=UUID=926fa7cc-6f97-4672-85a7-a1ed8f5bd842 ro rootflags=subvol=@ quiet splash intel_pstate=enable acpi_osi=intel vt.handoff=7
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/13/2014
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: G551JM.204
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: G551JM
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrG551JM.204:bd10/13/2014:svnASUSTeKCOMPUTERINC.:pnG551JM:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnG551JM:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
dmi.product.name: G551JM
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.
version.compiz: compiz 1:0.9.11.3+14.04.20141104-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.56-1~ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 10.1.3-0ubuntu0.3
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 10.1.3-0ubuntu0.3
version.xserver-xorg-core: xserver-xorg-core 2:1.15.1-0ubuntu2.6
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.8.2-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.3.0-1ubuntu3.1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.910-0ubuntu1.4
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.10-1ubuntu2
xserver.bootTime: Mon Feb 2 18:36:35 2015
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
 product id 12876
 vendor SDC
xserver.version: 2:1.15.1-0ubuntu2.6