cant launch qt, xrdp xfce4 ubuntu 20.04 server

elynx · 2 Sept 2021, 22:33

hello everyone.

my problem is that the app is not starting as it used to when i ran the code on my local windows machine.
i've tried different solutions i came across googling but i'm stuck.

error msg:

QObject::moveToThread: Current thread (0x23b3100) is not the object's thread (0x31bca90).
Cannot move to target thread (0x23b3100)

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/usr/local/lib/python3.8/dist-packages/cv2/qt/plugins" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: xcb, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl.

Aborted (core dumped)

ldd output:

/usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms$ ldd libqxcb.so 
	linux-vdso.so.1 (0x00007fff4a78a000)
	libQt5XcbQpa-70670cdb.so.5.15.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libQt5XcbQpa-70670cdb.so.5.15.0 (0x00007fd20885e000)
	libfreetype-8d3bcff4.so.6.14.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libfreetype-8d3bcff4.so.6.14.0 (0x00007fd20858e000)
	libz-d8a329de.so.1.2.7 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libz-d8a329de.so.1.2.7 (0x00007fd208377000)
	libQt5Gui-ca084835.so.5.15.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libQt5Gui-ca084835.so.5.15.0 (0x00007fd2079e0000)
	libQt5Core-d92f2856.so.5.15.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libQt5Core-d92f2856.so.5.15.0 (0x00007fd207288000)
	libGL.so.1 => /lib/x86_64-linux-gnu/libGL.so.1 (0x00007fd2071ee000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fd2071cb000)
	libX11-xcb-1ae4fd0e.so.1.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libX11-xcb-1ae4fd0e.so.1.0.0 (0x00007fd206fc8000)
	libxcb-icccm-413c9f41.so.4.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-icccm-413c9f41.so.4.0.0 (0x00007fd206dc2000)
	libxcb-image-e82a276d.so.0.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-image-e82a276d.so.0.0.0 (0x00007fd206bba000)
	libxcb-shm-7a199f70.so.0.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-shm-7a199f70.so.0.0.0 (0x00007fd2069b2000)
	libxcb-keysyms-21015570.so.1.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-keysyms-21015570.so.1.0.0 (0x00007fd2067ae000)
	libxcb-randr-a96a5a87.so.0.1.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-randr-a96a5a87.so.0.1.0 (0x00007fd206597000)
	libxcb-render-util-43ce00f5.so.0.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-render-util-43ce00f5.so.0.0.0 (0x00007fd206391000)
	libxcb-render-637b984a.so.0.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-render-637b984a.so.0.0.0 (0x00007fd20617d000)
	libxcb-shape-25c2b258.so.0.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-shape-25c2b258.so.0.0.0 (0x00007fd205f75000)
	libxcb-sync-89374f40.so.1.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-sync-89374f40.so.1.0.0 (0x00007fd205d6c000)
	libxcb-xfixes-9be3ba6f.so.0.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-xfixes-9be3ba6f.so.0.0.0 (0x00007fd205b60000)
	libxcb-xinerama-ae147f87.so.0.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-xinerama-ae147f87.so.0.0.0 (0x00007fd20595b000)
	libxcb-xkb-9ba31ab3.so.1.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-xkb-9ba31ab3.so.1.0.0 (0x00007fd205734000)
	libxcb.so.1 => /lib/x86_64-linux-gnu/libxcb.so.1 (0x00007fd205708000)
	libXext.so.6 => /lib/x86_64-linux-gnu/libXext.so.6 (0x00007fd2056f3000)
	libX11.so.6 => /lib/x86_64-linux-gnu/libX11.so.6 (0x00007fd2055b6000)
	libSM.so.6 => /lib/x86_64-linux-gnu/libSM.so.6 (0x00007fd2055ab000)
	libICE.so.6 => /lib/x86_64-linux-gnu/libICE.so.6 (0x00007fd20558d000)
	libxkbcommon-x11-c65ed502.so.0.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxkbcommon-x11-c65ed502.so.0.0.0 (0x00007fd205380000)
	libxkbcommon-71ae2972.so.0.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxkbcommon-71ae2972.so.0.0.0 (0x00007fd20513d000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fd205137000)
	libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fd204f55000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fd204e06000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fd204deb000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fd204bf9000)
	libgthread-2.0.so.0 => /lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007fd204bf2000)
	libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007fd204ac9000)
	libbz2-a273e504.so.1.0.6 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libbz2-a273e504.so.1.0.6 (0x00007fd2048b8000)
	libpng15-c2ffaf3d.so.15.13.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libpng15-c2ffaf3d.so.15.13.0 (0x00007fd204689000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fd208b11000)
	libGLdispatch.so.0 => /lib/x86_64-linux-gnu/libGLdispatch.so.0 (0x00007fd2045d1000)
	libGLX.so.0 => /lib/x86_64-linux-gnu/libGLX.so.0 (0x00007fd20459b000)
	libxcb-util-4d666913.so.1.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libxcb-util-4d666913.so.1.0.0 (0x00007fd204394000)
	libXau-00ec42fe.so.6.0.0 => /usr/local/lib/python3.8/dist-packages/cv2/qt/plugins/platforms/./../../../../opencv_python.libs/libXau-00ec42fe.so.6.0.0 (0x00007fd20418f000)
	libXau.so.6 => /lib/x86_64-linux-gnu/libXau.so.6 (0x00007fd204189000)
	libXdmcp.so.6 => /lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007fd204181000)
	libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007fd204176000)
	libbsd.so.0 => /lib/x86_64-linux-gnu/libbsd.so.0 (0x00007fd20415c000)

QT_DEBUG_PLUGINS=1 output:
https://pastebin.com/XhbviBML

I couldnt find an option to spoiler the text so i put it on pastebin, please excuse the length i am very new to linux and i really dont know what i am looking for.
i'm trying to run this on a server with slim display manager and xfce4 gui ontop of ubuntu 20.04 LTS.
i think i installed all of the requirements that i also installed on windows at least its starting and putting out text in my terminal window but on trying to load the gui it stops.

any help would be appreciated.

thank you!

eyllanesc · 9 Feb 2021, 22:34

@elynx Does your application use PyQt5 and opencv at the same time? See this post: https://stackoverflow.com/a/68417901/6622587

elynx · 2 Sept 2021, 23:20

@eyllanesc uhm, i am not importing opencv anywhere so i guess thats a no to your question regarding the stackoverflow link.

eyllanesc · E elynx 2 Sept 2021, 22:50

@elynx According to the log your program is using it, maybe one of your libraries does use it, could you indicate which libraries your app uses? If none of your libraries use opencv then it is advisable to uninstall that package or better: create a virtualenv where you only install the libraries you are going to use.

ChrisW67 · wrote on 2 Sept 2021, 23:21

If you are not importing OpenCV then this part of the path to all the Qt and OpenCV libraries should seem suspicious: ../opencv_python.libs/.... This where your failing plugin is coming from.

On my Ubuntu 20.04 box the system Qt libraries live under /usr/lib/x86_64-linux-gnu/... and the matching plugins further down under there .../qt5/plugins/platform/libqxcb.so. Mixing Qt libraries will not usually end well.

Assuming you want to be using the system Qt libraries, make sure you have libqt5gui5 package installed.

Look to see if you have an odd LD_LIBRARY_PATH environment variable or an odd directory mentioned in the /etc/ld.so.conf.d/* files.

elynx · wrote on 2 Sept 2021, 23:24

Not sure how relevant this is but i uninstalled opencv-python via pip and it started working and throwing a FilenotFound error at me, which is weird because i copypasted the whole directory from windows via Remote Desktop Connection over to Linux. However 1 folder named UI didnt make it and it also 'didnt get extracted' when i wanted to try copypasting and unzipping a zip file. but everything is fine now :)

like i said - linux newbie yay! thanks for your help @eyllanesc @ChrisW67 , without you i wouldnt have solved this!