One of the changes in KDE 4.8 was KWin’s new composition / effect toggle handling. As a side effect the power management profiles no longer turn off composition and effects when the AC cord is plugged out.
This behaviour may be fixed in the future, in the meantime, below is a simple workaround:
1. Create a shell script something like this:
#!/bin/bash
if [[ $1 == "on" ]]; then
if [[ "$(qdbus org.kde.kwin /KWin org.kde.KWin.compositingActive)" = "false" ]] ; then
qdbus org.kde.kwin /KWin org.kde.KWin.toggleCompositing
fi
elif [[ $1 == "off" ]]; then
if [[ "$(qdbus org.kde.kwin /KWin org.kde.KWin.compositingActive)" = "true" ]] ; then
qdbus org.kde.kwin /KWin org.kde.KWin.toggleCompositing
fi
else
echo "Usage: $0 [on|off]"
fi
2. Make the script executable (chmod +x) and test it from the command line
3. Go to ‘Energy Saving Settings’ and edit the default ‘On AC Power’ profile. Check ‘Run Script’ and type in:
/full path to your script/script_name on
4. Repeat the same for the “On Battery” profile, but this time pass the argument off
5. Finally test the script by disconnecting the AC power and note that KDE notifies that composition has been suspended. Also running the command:
qdbus org.kde.kwin /KWin org.kde.KWin.compositingActive
Should return ‘false’
Now you can enjoy extended battery life.
Hm, if I understood the post from Martin you don’t gain much if anything by disabling the effects. At least I didn’t see any difference here. But this article is still very useful to run other things, like the ones suggested by PowerTop app.
You’re right that there’s no point in turning off desktop effect, that’s the reason we turn *composition* off. Do a simple test, drag a window with composition on, use the script to turn it off and drag the window again, the effect should be noticeable