I had this in KDE SC 4 times already.

During playback of a movie with VLC the screen switches off after a while. This even happens when I disable screen blanking and screen switching off in *all* of the powerdevil energy profiles.

Reproducible: Always

Steps to Reproduce:
1. Play a movie with VLC.

Or

1. Disable screen blanking and switching off in all profiles.

Actual Results:  
Screen still blanks.

Even tough while playing a movie with VLC powerdevil plasma applet actually reported that VLC inhibits power saving.

Expected Results:  
Screen does not blank.

In KDE SC 4.14 times this helped:

martin@merkaba:~/bin#130> cat noblank.sh 
#!/bin/sh
while true; do qdbus org.kde.screensaver /ScreenSaver SimulateUserActivity ; sleep 60 ; done


But with Plasma 5 this script has no effect. The method is still available though.

Additionally I tried xset -dpms but it had no effect either.

I use activities, but none of it has special energy saving settings. So I expect the global settings to apply.



This happens on ThinkPad T520 with two screens:

martin@merkaba:~> phoronix-test-suite system-info

Phoronix Test Suite v5.2.1
System Information

Hardware:
Processor: Intel Core i5-2520M @ 3.20GHz (4 Cores), Motherboard: LENOVO 42433WG, Chipset: Intel 2nd Generation Core Family DRAM, Memory: 16384MB, Disk: 300GB INTEL SSDSA2CW30 + 480GB Crucial_CT480M50, Graphics: Intel HD 3000 (1300MHz), Audio: Conexant CX20590, Monitor: P24T-7 LED, Network: Intel 82579LM Gigabit Connection + Intel Centrino Advanced-N 6205

Software:
OS: Debian unstable, Kernel: 4.3.0-rc3-tp520-btrfstrim+ (x86_64), Desktop: KDE Frameworks 5, Display Server: X Server 1.17.2, Display Driver: intel 2.99.917, OpenGL: 3.3 Mesa 11.0.2, Compiler: GCC 5.2.1 20150911, File-System: btrfs, Screen Resolution: 3840x1080