If KSCREEN_BACKEND is not set, the KCM only shows "No kscreen backend found. Please check your kscreen installation." A workaround is explicitly setting the variable to e.g. "QScreen" or "XRandR". Line 137 in libkscreen/src/configoperation.cpp explicitly asks for the value of this env variable and has no fallback code if it is not set. However, kscreen-doctor tells me the correct preferred backend for my system: kscreen-doctor -b Environment: * KSCREEN_BACKEND is : [not set] * KSCREEN_BACKEND_INPROCESS : [not set] Preferred KScreen backend : KSC_XRandR.so Available KScreen backends: * KSC_Fake.so: /opt/kde/install/kf5/lib/x86_64-linux-gnu/plugins/kf5/kscreen/KSC_Fake.so * KSC_KWayland.so: /opt/kde/install/kf5/lib/x86_64-linux-gnu/plugins/kf5/kscreen/KSC_KWayland.so * KSC_QScreen.so: /opt/kde/install/kf5/lib/x86_64-linux-gnu/plugins/kf5/kscreen/KSC_QScreen.so * KSC_XRandR.so: /opt/kde/install/kf5/lib/x86_64-linux-gnu/plugins/kf5/kscreen/KSC_XRandR.so * KSC_XRandR11.so: /opt/kde/install/kf5/lib/x86_64-linux-gnu/plugins/kf5/kscreen/KSC_XRandR11.so Output of kscreen-console bug: cordlandwehr@weatherwax:~/.local5$ kscreen-console bug kscreen-console(26229)/(default) main: START: Requesting Config kscreen-console(26229)/(kscreen) KScreen::BackendManager::startBackend: starting external backend launcher for "" kscreen-console(26229)/(default) configReceived: Received config. Took 278 milliseconds ========================xrandr --verbose========================== Screen 0: minimum 8 x 8, current 3840 x 1080, maximum 32767 x 32767 eDP1 connected 1920x1080+0+0 (0x4d) normal (normal left inverted right x axis y axis) 309mm x 173mm Identifier: 0x43 Timestamp: 66102451 Subpixel: unknown Gamma: 1.0:1.0:1.0 Brightness: 1.0 Clones: CRTC: 0 CRTCs: 0 1 2 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: EDID: 00ffffffffffff0006af3d1200000000 00160104951f11780287e5a456509e26 0d505400000001010101010101010101 010101010101143780b8703824401010 3e0035ad100000180000000f00000000 00000000000000000020000000fe0041 554f0a202020202020202020000000fe 004231343048414e30312e32200a00a3 BACKLIGHT: 426 range: (0, 851) Backlight: 426 range: (0, 851) scaling mode: Full aspect supported: None, Full, Center, Full aspect Broadcast RGB: Automatic supported: Automatic, Full, Limited 16:235 audio: auto supported: force-dvi, off, auto, on 1920x1080 (0x4d) 141.000MHz -HSync -VSync *current +preferred h: width 1920 start 1936 end 1952 total 2104 skew 0 clock 67.02KHz v: height 1080 start 1083 end 1097 total 1116 clock 60.05Hz 1920x1080 (0xee) 138.500MHz +HSync -VSync h: width 1920 start 1968 end 2000 total 2080 skew 0 clock 66.59KHz v: height 1080 start 1083 end 1088 total 1111 clock 59.93Hz 1680x1050 (0xef) 146.250MHz -HSync +VSync h: width 1680 start 1784 end 1960 total 2240 skew 0 clock 65.29KHz v: height 1050 start 1053 end 1059 total 1089 clock 59.95Hz 1680x1050 (0xf0) 119.000MHz +HSync -VSync h: width 1680 start 1728 end 1760 total 1840 skew 0 clock 64.67KHz v: height 1050 start 1053 end 1059 total 1080 clock 59.88Hz 1600x1024 (0xf1) 103.125MHz +HSync +VSync h: width 1600 start 1600 end 1656 total 1664 skew 0 clock 61.97KHz v: height 1024 start 1024 end 1029 total 1030 clock 60.17Hz 1400x1050 (0xf2) 122.000MHz +HSync +VSync h: width 1400 start 1488 end 1640 total 1880 skew 0 clock 64.89KHz v: height 1050 start 1052 end 1064 total 1082 clock 59.98Hz 1600x900 (0xf3) 118.997MHz -HSync +VSync h: width 1600 start 1696 end 1864 total 2128 skew 0 clock 55.92KHz v: height 900 start 901 end 904 total 932 clock 60.00Hz 1280x1024 (0xf4) 108.000MHz +HSync +VSync h: width 1280 start 1328 end 1440 total 1688 skew 0 clock 63.98KHz v: height 1024 start 1025 end 1028 total 1066 clock 60.02Hz 1440x900 (0xf5) 106.500MHz -HSync +VSync h: width 1440 start 1520 end 1672 total 1904 skew 0 clock 55.93KHz v: height 900 start 903 end 909 total 934 clock 59.89Hz 1280x960 (0xf6) 108.000MHz +HSync +VSync h: width 1280 start 1376 end 1488 total 1800 skew 0 clock 60.00KHz v: height 960 start 961 end 964 total 1000 clock 60.00Hz 1368x768 (0xf7) 85.860MHz -HSync +VSync h: width 1368 start 1440 end 1584 total 1800 skew 0 clock 47.70KHz v: height 768 start 769 end 772 total 795 clock 60.00Hz 1360x768 (0xf8) 84.750MHz -HSync +VSync h: width 1360 start 1432 end 1568 total 1776 skew 0 clock 47.72KHz v: height 768 start 771 end 781 total 798 clock 59.80Hz 1360x768 (0xf9) 72.000MHz +HSync -VSync h: width 1360 start 1408 end 1440 total 1520 skew 0 clock 47.37KHz v: height 768 start 771 end 781 total 790 clock 59.96Hz 1152x864 (0xfa) 81.620MHz -HSync +VSync h: width 1152 start 1216 end 1336 total 1520 skew 0 clock 53.70KHz v: height 864 start 865 end 868 total 895 clock 60.00Hz 1280x720 (0xfb) 74.480MHz -HSync +VSync h: width 1280 start 1336 end 1472 total 1664 skew 0 clock 44.76KHz v: height 720 start 721 end 724 total 746 clock 60.00Hz 1024x768 (0xfc) 65.000MHz -HSync -VSync h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.36KHz v: height 768 start 771 end 777 total 806 clock 60.00Hz 1024x576 (0xfd) 46.995MHz -HSync +VSync h: width 1024 start 1064 end 1168 total 1312 skew 0 clock 35.82KHz v: height 576 start 577 end 580 total 597 clock 60.00Hz 960x540 (0xfe) 40.784MHz -HSync +VSync h: width 960 start 992 end 1088 total 1216 skew 0 clock 33.54KHz v: height 540 start 541 end 544 total 559 clock 60.00Hz 800x600 (0xff) 40.000MHz +HSync +VSync h: width 800 start 840 end 968 total 1056 skew 0 clock 37.88KHz v: height 600 start 601 end 605 total 628 clock 60.32Hz 800x600 (0x100) 36.000MHz +HSync +VSync h: width 800 start 824 end 896 total 1024 skew 0 clock 35.16KHz v: height 600 start 601 end 603 total 625 clock 56.25Hz 864x486 (0x101) 32.901MHz -HSync +VSync h: width 864 start 888 end 976 total 1088 skew 0 clock 30.24KHz v: height 486 start 487 end 490 total 504 clock 60.00Hz 640x480 (0x102) 25.175MHz -HSync -VSync h: width 640 start 656 end 752 total 800 skew 0 clock 31.47KHz v: height 480 start 490 end 492 total 525 clock 59.94Hz 720x405 (0x103) 22.176MHz -HSync +VSync h: width 720 start 728 end 800 total 880 skew 0 clock 25.20KHz v: height 405 start 406 end 409 total 420 clock 60.00Hz 640x360 (0x104) 17.187MHz -HSync +VSync h: width 640 start 640 end 704 total 768 skew 0 clock 22.38KHz v: height 360 start 361 end 364 total 373 clock 60.00Hz DP1 disconnected (normal left inverted right x axis y axis) Identifier: 0x44 Timestamp: 66102451 Subpixel: unknown Clones: HDMI1 CRTCs: 0 1 2 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: Broadcast RGB: Automatic supported: Automatic, Full, Limited 16:235 audio: auto supported: force-dvi, off, auto, on DP2 disconnected (normal left inverted right x axis y axis) Identifier: 0x45 Timestamp: 66102451 Subpixel: unknown Clones: HDMI2 CRTCs: 0 1 2 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: Broadcast RGB: Automatic supported: Automatic, Full, Limited 16:235 audio: auto supported: force-dvi, off, auto, on DP2-1 disconnected (normal left inverted right x axis y axis) Identifier: 0x46 Timestamp: 66102451 Subpixel: unknown Clones: DP2-2 DP2-3 CRTCs: 0 1 2 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: Broadcast RGB: Automatic supported: Automatic, Full, Limited 16:235 audio: auto supported: force-dvi, off, auto, on DP2-2 connected 1920x1080+1920+0 (0x4e) normal (normal left inverted right x axis y axis) 621mm x 341mm Identifier: 0x47 Timestamp: 66102451 Subpixel: unknown Gamma: 1.0:1.0:1.0 Brightness: 1.0 Clones: DP2-1 DP2-3 CRTC: 1 CRTCs: 0 1 2 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: EDID: 00ffffffffffff000469e42777750000 19190103803c22782a53a5a756529c26 115054bfef00d1c0b300950081808140 81c0714f0101023a801871382d40582c 45006d552100001e000000ff0046364c 4d544a3033303037310a000000fd0032 4b185311000a202020202020000000fc 00415355532056583237390a20200194 020322714f0102031112130414050e0f 1d1e1f90230917078301000065030c00 10008c0ad08a20e02d10103e96006d55 21000018011d007251d01e206e285500 6d552100001e011d00bc52d01e20b828 55406d552100001e8c0ad09020403120 0c4055006d5521000018000000000000 0000000000000000000000000000008d Broadcast RGB: Automatic supported: Automatic, Full, Limited 16:235 audio: auto supported: force-dvi, off, auto, on 1920x1080 (0x4e) 148.500MHz +HSync +VSync *current +preferred h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 67.50KHz v: height 1080 start 1084 end 1089 total 1125 clock 60.00Hz 1920x1080 (0x105) 148.500MHz +HSync +VSync h: width 1920 start 2448 end 2492 total 2640 skew 0 clock 56.25KHz v: height 1080 start 1084 end 1089 total 1125 clock 50.00Hz 1920x1080 (0x106) 148.352MHz +HSync +VSync h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 67.43KHz v: height 1080 start 1084 end 1089 total 1125 clock 59.94Hz 1680x1050 (0xf0) 119.000MHz +HSync -VSync h: width 1680 start 1728 end 1760 total 1840 skew 0 clock 64.67KHz v: height 1050 start 1053 end 1059 total 1080 clock 59.88Hz 1280x1024 (0x107) 135.000MHz +HSync +VSync h: width 1280 start 1296 end 1440 total 1688 skew 0 clock 79.98KHz v: height 1024 start 1025 end 1028 total 1066 clock 75.02Hz 1280x1024 (0xf4) 108.000MHz +HSync +VSync h: width 1280 start 1328 end 1440 total 1688 skew 0 clock 63.98KHz v: height 1024 start 1025 end 1028 total 1066 clock 60.02Hz 1440x900 (0x108) 88.750MHz +HSync -VSync h: width 1440 start 1488 end 1520 total 1600 skew 0 clock 55.47KHz v: height 900 start 903 end 909 total 926 clock 59.90Hz 1280x960 (0xf6) 108.000MHz +HSync +VSync h: width 1280 start 1376 end 1488 total 1800 skew 0 clock 60.00KHz v: height 960 start 961 end 964 total 1000 clock 60.00Hz 1152x864 (0x109) 108.000MHz +HSync +VSync h: width 1152 start 1216 end 1344 total 1600 skew 0 clock 67.50KHz v: height 864 start 865 end 868 total 900 clock 75.00Hz 1280x720 (0x10a) 74.250MHz +HSync +VSync h: width 1280 start 1390 end 1430 total 1650 skew 0 clock 45.00KHz v: height 720 start 725 end 730 total 750 clock 60.00Hz 1280x720 (0x10b) 74.250MHz +HSync +VSync h: width 1280 start 1720 end 1760 total 1980 skew 0 clock 37.50KHz v: height 720 start 725 end 730 total 750 clock 50.00Hz 1280x720 (0x10c) 74.176MHz +HSync +VSync h: width 1280 start 1390 end 1430 total 1650 skew 0 clock 44.96KHz v: height 720 start 725 end 730 total 750 clock 59.94Hz 1440x576 (0x10d) 54.000MHz -HSync -VSync h: width 1440 start 1464 end 1592 total 1728 skew 0 clock 31.25KHz v: height 576 start 581 end 586 total 625 clock 50.00Hz 1024x768 (0x10e) 78.750MHz +HSync +VSync h: width 1024 start 1040 end 1136 total 1312 skew 0 clock 60.02KHz v: height 768 start 769 end 772 total 800 clock 75.03Hz 1024x768 (0x10f) 75.000MHz -HSync -VSync h: width 1024 start 1048 end 1184 total 1328 skew 0 clock 56.48KHz v: height 768 start 771 end 777 total 806 clock 70.07Hz 1024x768 (0xfc) 65.000MHz -HSync -VSync h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.36KHz v: height 768 start 771 end 777 total 806 clock 60.00Hz 1440x480 (0x110) 54.054MHz -HSync -VSync h: width 1440 start 1472 end 1596 total 1716 skew 0 clock 31.50KHz v: height 480 start 489 end 495 total 525 clock 60.00Hz 1440x480 (0x111) 54.000MHz -HSync -VSync h: width 1440 start 1472 end 1596 total 1716 skew 0 clock 31.47KHz v: height 480 start 489 end 495 total 525 clock 59.94Hz 832x624 (0x112) 57.284MHz -HSync -VSync h: width 832 start 864 end 928 total 1152 skew 0 clock 49.73KHz v: height 624 start 625 end 628 total 667 clock 74.55Hz 800x600 (0x113) 50.000MHz +HSync +VSync h: width 800 start 856 end 976 total 1040 skew 0 clock 48.08KHz v: height 600 start 637 end 643 total 666 clock 72.19Hz 800x600 (0x114) 49.500MHz +HSync +VSync h: width 800 start 816 end 896 total 1056 skew 0 clock 46.88KHz v: height 600 start 601 end 604 total 625 clock 75.00Hz 800x600 (0xff) 40.000MHz +HSync +VSync h: width 800 start 840 end 968 total 1056 skew 0 clock 37.88KHz v: height 600 start 601 end 605 total 628 clock 60.32Hz 800x600 (0x100) 36.000MHz +HSync +VSync h: width 800 start 824 end 896 total 1024 skew 0 clock 35.16KHz v: height 600 start 601 end 603 total 625 clock 56.25Hz 720x576 (0x115) 27.000MHz -HSync -VSync h: width 720 start 732 end 796 total 864 skew 0 clock 31.25KHz v: height 576 start 581 end 586 total 625 clock 50.00Hz 720x480 (0x116) 27.027MHz -HSync -VSync h: width 720 start 736 end 798 total 858 skew 0 clock 31.50KHz v: height 480 start 489 end 495 total 525 clock 60.00Hz 720x480 (0x117) 27.000MHz -HSync -VSync h: width 720 start 736 end 798 total 858 skew 0 clock 31.47KHz v: height 480 start 489 end 495 total 525 clock 59.94Hz 640x480 (0x118) 31.500MHz -HSync -VSync h: width 640 start 656 end 720 total 840 skew 0 clock 37.50KHz v: height 480 start 481 end 484 total 500 clock 75.00Hz 640x480 (0x119) 31.500MHz -HSync -VSync h: width 640 start 664 end 704 total 832 skew 0 clock 37.86KHz v: height 480 start 489 end 492 total 520 clock 72.81Hz 640x480 (0x11a) 30.240MHz -HSync -VSync h: width 640 start 704 end 768 total 864 skew 0 clock 35.00KHz v: height 480 start 483 end 486 total 525 clock 66.67Hz 640x480 (0x11b) 25.200MHz -HSync -VSync h: width 640 start 656 end 752 total 800 skew 0 clock 31.50KHz v: height 480 start 490 end 492 total 525 clock 60.00Hz 640x480 (0x102) 25.175MHz -HSync -VSync h: width 640 start 656 end 752 total 800 skew 0 clock 31.47KHz v: height 480 start 490 end 492 total 525 clock 59.94Hz 720x400 (0x11c) 28.320MHz -HSync +VSync h: width 720 start 738 end 846 total 900 skew 0 clock 31.47KHz v: height 400 start 412 end 414 total 449 clock 70.08Hz DP2-3 disconnected (normal left inverted right x axis y axis) Identifier: 0x48 Timestamp: 66102451 Subpixel: unknown Clones: DP2-1 DP2-2 CRTCs: 0 1 2 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: Broadcast RGB: Automatic supported: Automatic, Full, Limited 16:235 audio: auto supported: force-dvi, off, auto, on HDMI1 disconnected (normal left inverted right x axis y axis) Identifier: 0x49 Timestamp: 66102451 Subpixel: unknown Clones: DP1 CRTCs: 0 1 2 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: aspect ratio: Automatic supported: Automatic, 4:3, 16:9 Broadcast RGB: Automatic supported: Automatic, Full, Limited 16:235 audio: auto supported: force-dvi, off, auto, on HDMI2 disconnected (normal left inverted right x axis y axis) Identifier: 0x4a Timestamp: 66102451 Subpixel: unknown Clones: DP2 CRTCs: 0 1 2 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: aspect ratio: Automatic supported: Automatic, 4:3, 16:9 Broadcast RGB: Automatic supported: Automatic, Full, Limited 16:235 audio: auto supported: force-dvi, off, auto, on VIRTUAL1 disconnected (normal left inverted right x axis y axis) Identifier: 0x4b Timestamp: 66102451 Subpixel: no subpixels Clones: CRTCs: 3 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: ========================Outputs=================================== kscreen-console(26229)/(default) Console::printConfig: Config is invalid, probably backend couldn't load ========================Configurations============================ kscreen-console(26229)/(default) Console::printSerializations: Configs in: "/home/cordlandwehr/.local5/kscreen/" kscreen-console(26229)/(default) Console::printSerializations: Number of files: 0 Reproducible: Always
I'm a bit puzzled. kscreen-doctor and the kscreen KCM use the same method to load the backend (GetConfigOperation). GetConfigOperation internally asks the backendmanager for the preferred backend, if that's xrandr, it loads the plugin out of process, any other backend loads in process. On X11, it should never actually hit configoperation.cpp:137 since that's the in-process codepath, are you sure it goes through that function? backendmanager.cpp decides in its ctor which method (InProcess / OutOfProcess it uses), after choosing the backend plugin. Moreover, it works on my system as expected, no KSCREEN_BACKEND env var is set.
You are right; I looked at the wrong code location. Here is a probably more verbose output. I now generated a backtrace for getting the debug message: kcmshell5(30793)/(kscreen) KScreen::BackendManager::startBackend: starting external backend launcher for "" At this point, I have (added an assert in "/opt/kde/src/kde/workspace/libkscreen/src/backendmanager.cpp", line=291): #5 0x00007fffda2f3bc6 in KScreen::BackendManager::startBackend(QString const&, QMap<QString, QVariant> const&) (this=0x6af270, backend=..., arguments=...) at /opt/kde/src/kde/workspace/libkscreen/src/backendmanager.cpp:291 #6 0x00007fffda2f3aca in KScreen::BackendManager::requestBackend() (this=0x6af270) at /opt/kde/src/kde/workspace/libkscreen/src/backendmanager.cpp:276 #7 0x00007fffda2fe5cb in KScreen::ConfigOperationPrivate::requestBackend() (this=0x9265f0) at /opt/kde/src/kde/workspace/libkscreen/src/configoperation.cpp:45 #8 0x00007fffda30019e in KScreen::GetConfigOperation::start() (this=0x92bfd0) at /opt/kde/src/kde/workspace/libkscreen/src/getconfigoperation.cpp:178 #9 0x00007fffda315dcd in KScreen::ConfigOperation::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (_o=0x92bfd0, _c=QMetaObject::InvokeMetaMethod, _id=1, _a=0x92bd10) at /opt/kde/build/kde/workspace/libkscreen/src/moc_configoperation.cpp:81 #10 0x00007ffff4d8ad07 in QMetaCallEvent::placeMetaCall(QObject*) (this=0x93afb0, object=0x92bfd0) at kernel/qobject.cpp:495 #11 0x00007ffff4d8bda0 in QObject::event(QEvent*) (this=0x92bfd0, e=0x93afb0) at kernel/qobject.cpp:1256 #12 0x00007ffff594a4f2 in QApplicationPrivate::notify_helper(QObject*, QEvent*) (this=0x61a250, receiver=0x92bfd0, e=0x93afb0) at kernel/qapplication.cpp:3804 #13 0x00007ffff59478bd in QApplication::notify(QObject*, QEvent*) (this=0x7fffffffd1f0, receiver=0x92bfd0, e=0x93afb0) at kernel/qapplication.cpp:3163 #14 0x00007ffff4d51bfa in QCoreApplication::notifyInternal2(QObject*, QEvent*) (receiver=0x92bfd0, event=0x93afb0) at kernel/qcoreapplication.cpp:1015 #15 0x00007ffff4d55c30 in QCoreApplication::sendEvent(QObject*, QEvent*) (receiver=0x92bfd0, event=0x93afb0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:225 #16 0x00007ffff4d52fe2 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (receiver=0x0, event_type=0, data=0x6190d0) at kernel/qcoreapplication.cpp:1650 #17 0x00007ffff4d52962 in QCoreApplication::sendPostedEvents(QObject*, int) (receiver=0x0, event_type=0) at kernel/qcoreapplication.cpp:1508 #18 0x00007ffff4dcbb2c in postEventSourceDispatch(GSource*, GSourceFunc, gpointer) (s=0x672fb0) at kernel/qeventdispatcher_glib.cpp:270 #19 0x00007fffed56a1a7 in g_main_context_dispatch (context=0x7fffdc0016f0) at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gmain.c:3154 #20 0x00007fffed56a1a7 in g_main_context_dispatch (context=context@entry=0x7fffdc0016f0) at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gmain.c:3769 #21 0x00007fffed56a400 in g_main_context_iterate (context=context@entry=0x7fffdc0016f0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gmain.c:3840 ---Type <return> to continue, or q <return> to quit--- #22 0x00007fffed56a4ac in g_main_context_iteration (context=0x7fffdc0016f0, may_block=1) at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gmain.c:3901 #23 0x00007ffff4dcc305 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x67ceb0, flags=...) at kernel/qeventdispatcher_glib.cpp:417 #24 0x00007fffe78cce86 in QPAEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x67ceb0, flags=...) at eventdispatchers/qeventdispatcher_glib.cpp:115 #25 0x00007ffff4d4e570 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7fffffffd050, flags=...) at kernel/qeventloop.cpp:128 #26 0x00007ffff4d4e86c in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7fffffffd050, flags=...) at kernel/qeventloop.cpp:204 #27 0x00007ffff4d52344 in QCoreApplication::exec() () at kernel/qcoreapplication.cpp:1285 #28 0x00007ffff517d598 in QGuiApplication::exec() () at kernel/qguiapplication.cpp:1607 #29 0x00007ffff59472a1 in QApplication::exec() () at kernel/qapplication.cpp:2979 #30 0x00007ffff7bd4210 in kdemain(int, char**) (_argc=2, _argv=0x7fffffffdb18) at /opt/kde/src/kde/workspace/kde-cli-tools/kcmshell/main.cpp:294 #31 0x00000000004009a8 in main(int, char**) (argc=2, argv=0x7fffffffdb18) at /opt/kde/build/kde/workspace/kde-cli-tools/kcmshell/kcmshell5_dummy.cpp:3
After some major cleanup of my .config and .local directories (grown since the first Qt5 based pre-alpha versions), I cannot reproduce this issue anymore. So, I will close it.
I have this problem currently after doing a KDE5 custom build to /opt/kde5. I first thought it was due to conflicts with system KDE but after removing that kscreen still didn't work. Fortunately I found this bug and setting KSCREEN_BACKEND manually makes the kcm owrk.
carewolf@twilight% systemsettings5 org.kde.kactivities.lib.core: Killing the consumer kscreen: Failed to request backend: "org.freedesktop.DBus.Error.ServiceUnknown" : "The name org.kde.KScreen was not provided by any .service files" org.kde.kactivities.lib.core: Killing the consumer org.kde.kactivities.lib.core: Killing the consumer carewolf@twilight% export KSCREEN_BACKEND=KSC_XRandR.so carewolf@twilight% systemsettings5 org.kde.kactivities.lib.core: Killing the consumer carewolf@twilight%