When set screen off automatically, the screen will turn black first, then turn on quickly and then turn black again. My graphic card is intel. I suspect this is caused by the new feature of powerdevil invoking kwin effect. Reproducible: Sometimes
The effect kicks in 5 seconds before turning off the screen but will automatically end after 8 seconds to prevent blocking the workspace. Perhaps your screen takes longer to suspend and the effect quits prior to that.
Emm, I don't know. I also noticed that this also happens when I use keyboard to decreaes the brightness to zero, as shown in the video: http://youtu.be/9vdwxsO_zW8
Git commit 1005dd9a25c5fafea1f781c6d2a49fe99e219a34 by Weng Xuetian. Committed on 12/09/2015 at 01:28. Pushed by xuetianweng into branch 'Plasma/5.4'. Fix the brightness update 1. Update to m_cachedBrightnessMap is ignored during the animation. This change queries the real brightness after animation is finished. 2. setting start/endvalue will also trigger the valueChanged in QPropertyAnimation, disconnect the slot on valueChanged after stop() and reconnect it before start(). Related: bug 350676 REVIEW: 125156 FIXED-IN: 5.4.2 M +3 -0 daemon/backends/upower/powerdevilupowerbackend.cpp http://commits.kde.org/powerdevil/1005dd9a25c5fafea1f781c6d2a49fe99e219a34