When kde tries to lower the screen brightness due to user idleness, kded4 updates its user time (_NET_WM_USER_TIME) property to the time when kde was started.
Because recent xscreensaver (>= version 5.33) monitors update of USER_TIME, the password dialog will be brought up every 150 seconds when it sees the USER_TIME update of kded4, so the screen is never powered down, and the password dialog of xscreensaver pops up repeatedly.


Reproducible: Always

Steps to Reproduce:
1. Start kde4 with kdelibs-4.14.6 and kde-workspace-4.11.17 (may also apply to other versions);
2. Activate xscreensaver (>= version 5.33) with xscreensaver-command -activate or -lock;
3. Wait for a few minutes (150s in my case) for kde to try to lower the screen brightness.

Actual Results:  
Screen brightness stayed the same, and the password dialog of xscreensaver was brought up.

Expected Results:  
Screen brightness is lowered.

This happens 100% of the time on a ThinkPad laptop, and almost 100% on a desktop computer. Because it is impossible to let xscreensaver monitor USER_TIME update "optionally", any update of this window property will break its idleness test. So ... can kded not update USER_TIME on power events -- especially on kde's self-generated power events (i.e., not from the user pressing Fn+Home/End and alike)?