Comment # 6 on bug 960474 from Egbert Eich

> #!/bin/sh
>     xset dpms 0 0 0
>     xset -dpms
>     xset s noblank
> 
> I consider this post [SOLVED].

Sure, this works if you don't want any DPMS (screen power saving) or blanking
at all. Normally, you want the screen to blank when idle, however. Just not
when playing a movie or giving a presentation. In this situation your player or
presentation tool should put your desktop in presentation mode. The desktop
then performs exactly these actions and prevents the screen saver / screen lock
from kicking in.
If you need to find a solution which works for you you need to ask at the
forums.
if you believe there is a real bug somewhere you should report it here.
Whether there is a bug in either the KDE desktop or vlc I cannot say right off
hand. To determine this, the ticket was why this got reassigned to the vlc
maintainer.