[SOLVED] qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in ""

hskoglund

Hi, I think @raven-worx is on to something here, there's a problem with the location of Qt's files, but not a problem for libqxb.so for finding the .dlls it needs (that's why the ldd looks good) but rather a problem for your executable file urh to find the location of Qt's plugin files.

I think you need to give urh a helping hand by creating a qt.conf file with this contents:

[Paths]
Plugins=/usr/lib/qt/plugins

and place qt.conf in the same directory as the urh executable file

PieBru

@hskoglund
I'm on Arch Linux, no luck by placing qt.conf in ~/.config/urh/ (together with urh.ini) and /usr/bin/ (where is located the urh executable).

$ urh
Warning: Ignoring XDG_SESSION_TYPE=wayland on Gnome. Use QT_QPA_PLATFORM=wayland to run on Wayland anyway.
qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in ""
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Aborted (core dumped)

hskoglund

No worries, there are other ways of setting the path, for example you could try exporting it as an environment variable, say like this:

export QT_PLUGIN_PATH=/usr/lib/qt/plugins
urh

If that doesn't work, also you can specify the path to libqxcb.so with a command argument to urh, like this:

urh -platformpluginpath /usr/lib/qt/plugins/platforms

(Note: this 2nd example only helps out with locating libqxcb.so, i.e. if urh needs more plugins to be loaded (and the 1st example above doesn't work) your still out of luck.)

PieBru

@hskoglund
Thank you much, both solutions works here!!!
The urh command now shows only the wayland warning, but it seems not harmful as the app window appears and it seems to work as expected.

Warning: Ignoring XDG_SESSION_TYPE=wayland on Gnome. Use QT_QPA_PLATFORM=wayland to run on Wayland anyway.

Thank you again,
Piero

PabloC

@hskoglund Hi sorry for the question but, what is urh, i try to find information about it but i dont got it, i have te same problem but i cant find the urh thing, thanks!

hskoglund

Hi, look at the first post on this page, urh stands for Universal Radio Hacker...

PabloC

@hskoglund Thanks!

NoWhereMan1979

@hskoglund said in [SOLVED] qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in "":

export QT_PLUGIN_PATH=/usr/lib/qt/plugins

Hi dear @hskoglund
Your efficient advises helped me too. just wanted to thank you.

goksan.isil

@NoWhereMan1979 said in [SOLVED] qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in "":

@hskoglund

@hskoglund your export QT_PLUGIN_PATH=/usr/lib/qt/plugins advice has helped me too. THank you!

mol_

@hskoglund thank you, I have tried your mentioned method and it works well.

export QT_PLUGIN_PATH=/usr/lib/qt/plugins

superdummy

Hi,
I experienced this problem on Debian 10 Buster after upgrading my Qt to 5.15.2 and QtCreator to 14.0
In the end the lib libxcb-util.so.1 was missing.

ldd /home/developer/Qt5/5.15.2/gcc_64/plugins/platforms/libqxcb.so
...
libxcb-util.so.1 => not found
...

See here: https://bugreports.qt.io/browse/QTBUG-88688

andreionea

@superdummy worked for me

LiZheCN

I stuck at this issue too.

I set the environment variable export QT_PLUGIN_PATH=/usr/lib/qt/plugins.
but not work.

I run a python script use pyqt. Get the error message:

QObject::moveToThread: Current thread (0x55e4e5df2060) is not the object's thread (0x55e4e61624e0).
Cannot move to target thread (0x55e4e5df2060)

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/lizhe/.local/lib/python3.10/site-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.

Aborted (core dumped)

There is a file /home/lizhe/.local/lib/python3.10/site-packages/cv2/qt/plugins/platforms/libqxcb.so I move the libqxcb.so in upper dir, not work either.

output of ldd /usr/lib/qt/plugins/platforms/libqxcb.so


	linux-vdso.so.1 (0x00007ffe049cc000)
	libQt5XcbQpa.so.5 => /usr/lib/libQt5XcbQpa.so.5 (0x00007f11af265000)
	libQt5Gui.so.5 => /usr/lib/libQt5Gui.so.5 (0x00007f11aebff000)
	libQt5Core.so.5 => /usr/lib/libQt5Core.so.5 (0x00007f11ae6e1000)
	libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007f11ae4cb000)
	libc.so.6 => /usr/lib/libc.so.6 (0x00007f11ae2ff000)
	libfontconfig.so.1 => /usr/lib/libfontconfig.so.1 (0x00007f11ae2b0000)
	libfreetype.so.6 => /usr/lib/libfreetype.so.6 (0x00007f11ae1e3000)
	libQt5DBus.so.5 => /usr/lib/libQt5DBus.so.5 (0x00007f11ae163000)
	libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007f11ae142000)
	libX11-xcb.so.1 => /usr/lib/libX11-xcb.so.1 (0x00007f11ae13d000)
	libxcb-icccm.so.4 => /usr/lib/libxcb-icccm.so.4 (0x00007f11ae137000)
	libxcb-image.so.0 => /usr/lib/libxcb-image.so.0 (0x00007f11ae131000)
	libxcb-shm.so.0 => /usr/lib/libxcb-shm.so.0 (0x00007f11ae12a000)
	libxcb-keysyms.so.1 => /usr/lib/libxcb-keysyms.so.1 (0x00007f11ae125000)
	libxcb-randr.so.0 => /usr/lib/libxcb-randr.so.0 (0x00007f11ae113000)
	libxcb-render-util.so.0 => /usr/lib/libxcb-render-util.so.0 (0x00007f11ae10d000)
	libxcb-render.so.0 => /usr/lib/libxcb-render.so.0 (0x00007f11ae0fd000)
	libxcb-shape.so.0 => /usr/lib/libxcb-shape.so.0 (0x00007f11ae0f8000)
	libxcb-sync.so.1 => /usr/lib/libxcb-sync.so.1 (0x00007f11ae0ec000)
	libxcb-xfixes.so.0 => /usr/lib/libxcb-xfixes.so.0 (0x00007f11ae0e2000)
	libxcb-xinerama.so.0 => /usr/lib/libxcb-xinerama.so.0 (0x00007f11ae0dd000)
	libxcb-xkb.so.1 => /usr/lib/libxcb-xkb.so.1 (0x00007f11ae0bf000)
	libxcb-xinput.so.0 => /usr/lib/libxcb-xinput.so.0 (0x00007f11ae09a000)
	libxcb.so.1 => /usr/lib/libxcb.so.1 (0x00007f11ae070000)
	libX11.so.6 => /usr/lib/libX11.so.6 (0x00007f11adf2c000)
	libSM.so.6 => /usr/lib/libSM.so.6 (0x00007f11adf22000)
	libICE.so.6 => /usr/lib/libICE.so.6 (0x00007f11adf05000)
	libxkbcommon-x11.so.0 => /usr/lib/libxkbcommon-x11.so.0 (0x00007f11adefb000)
	libxkbcommon.so.0 => /usr/lib/libxkbcommon.so.0 (0x00007f11adeb2000)
	libglib-2.0.so.0 => /usr/lib/libglib-2.0.so.0 (0x00007f11add76000)
	libm.so.6 => /usr/lib/libm.so.6 (0x00007f11adc30000)
	libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007f11adc15000)
	libGL.so.1 => /usr/lib/libGL.so.1 (0x00007f11adb8f000)
	libpng16.so.16 => /usr/lib/libpng16.so.16 (0x00007f11adb58000)
	libz.so.1 => /usr/lib/libz.so.1 (0x00007f11adb3e000)
	libharfbuzz.so.0 => /usr/lib/libharfbuzz.so.0 (0x00007f11ada65000)
	libmd4c.so.0 => /usr/lib/libmd4c.so.0 (0x00007f11ada4d000)
	libsystemd.so.0 => /usr/lib/libsystemd.so.0 (0x00007f11ad971000)
	libdouble-conversion.so.3 => /usr/lib/libdouble-conversion.so.3 (0x00007f11ad95b000)
	libicui18n.so.70 => /usr/lib/libicui18n.so.70 (0x00007f11ad635000)
	libicuuc.so.70 => /usr/lib/libicuuc.so.70 (0x00007f11ad439000)
	libdl.so.2 => /usr/lib/libdl.so.2 (0x00007f11ad432000)
	libpcre2-16.so.0 => /usr/lib/libpcre2-16.so.0 (0x00007f11ad3a3000)
	libzstd.so.1 => /usr/lib/libzstd.so.1 (0x00007f11ad2cc000)
	/usr/lib64/ld-linux-x86-64.so.2 (0x00007f11af3c5000)
	libexpat.so.1 => /usr/lib/libexpat.so.1 (0x00007f11ad29c000)
	libbz2.so.1.0 => /usr/lib/libbz2.so.1.0 (0x00007f11ad289000)
	libbrotlidec.so.1 => /usr/lib/libbrotlidec.so.1 (0x00007f11ad27b000)
	libdbus-1.so.3 => /usr/lib/libdbus-1.so.3 (0x00007f11ad224000)
	libxcb-util.so.1 => /usr/lib/libxcb-util.so.1 (0x00007f11ad21c000)
	libXau.so.6 => /usr/lib/libXau.so.6 (0x00007f11ad217000)
	libXdmcp.so.6 => /usr/lib/libXdmcp.so.6 (0x00007f11ad20f000)
	libuuid.so.1 => /usr/lib/libuuid.so.1 (0x00007f11ad206000)
	libpcre.so.1 => /usr/lib/libpcre.so.1 (0x00007f11ad18d000)
	libGLdispatch.so.0 => /usr/lib/libGLdispatch.so.0 (0x00007f11ad0d5000)
	libGLX.so.0 => /usr/lib/libGLX.so.0 (0x00007f11ad0a2000)
	libgraphite2.so.3 => /usr/lib/libgraphite2.so.3 (0x00007f11ad07d000)
	librt.so.1 => /usr/lib/librt.so.1 (0x00007f11ad072000)
	liblzma.so.5 => /usr/lib/liblzma.so.5 (0x00007f11ad047000)
	liblz4.so.1 => /usr/lib/liblz4.so.1 (0x00007f11ad024000)
	libcap.so.2 => /usr/lib/libcap.so.2 (0x00007f11ad018000)
	libgcrypt.so.20 => /usr/lib/libgcrypt.so.20 (0x00007f11acedc000)
	libicudata.so.70 => /usr/lib/libicudata.so.70 (0x00007f11ab2c0000)
	libbrotlicommon.so.1 => /usr/lib/libbrotlicommon.so.1 (0x00007f11ab29b000)
	libgpg-error.so.0 => /usr/lib/libgpg-error.so.0 (0x00007f11ab273000)

System information:

 OS: Manjaro 21.2.2 Qonos
 Kernel: x86_64 Linux 5.15.16-1-MANJARO
 Uptime: 5h 18m
 Packages: 1396
 Shell: fish 3.3.1
 Resolution: 3840x1080
 DE: KDE5 / Plasma
 WM: KWin
 GTK Theme: Breeze [GTK2/3]
 Icon Theme: breeze-dark
 Disk: 31G / 236G (14%)
 CPU: Intel Core i7-7700K @ 8x 4.5GHz [44.0°C]
 GPU: Intel Corporation HD Graphics 630 (rev 04)
 RAM: 6722MiB / 15866MiB
 Python 3.10.1

hskoglund

Hi, do you get the same error if you try a vanilla Hello World python app?
Say like this:

app = QApplication(sys,argv)
window = QWidget()
window.setWindowTitle('Hello world')
window.setGeometry(100, 100, 640, 480)
window.show()
sys.exit(app.exec_())

LiZheCN

@hskoglund Without reboot a simple qt hello world project can run. After reboot every thing goes fine. Thank you for you time.

LiZheCN

@hskoglund Sorry to bother you again, the issue keep coming out after somethime. And I dont know how to solve it, for now.
I cant start my kate(build-in editor in manajaro)

And the error message is:

QObject::moveToThread: Current thread (0x55b676c29770) is not the object's thread (0x55b676c337c0).
Cannot move to target thread (0x55b676c29770)

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/lizhe/.local/lib/python3.10/site-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.

fish: Job 1, 'kate' terminated by signal SIGABRT (Abort)

After the reboot the issue is gone for just a while. How to solve it?

My system info is:

 OS: Manjaro 21.2.2 Qonos
 Kernel: x86_64 Linux 5.15.16-1-MANJARO
 Uptime: 8h 2m
 Packages: 1397
 Shell: python
 Resolution: 3840x1080
 DE: KDE5 / Plasma 
 WM: KWin
 GTK Theme: Breeze [GTK2/3]
 Icon Theme: breeze-dark
 Disk: 33G / 236G (15%)
 CPU: Intel Core i7-7700K @ 8x 4.5GHz [56.0°C]
 GPU: Intel Corporation HD Graphics 630 (rev 04)
 RAM: 7016MiB / 15866MiB

Python 3.10.1

NVIM v0.6.1
Build type: Release
LuaJIT 2.0.5
Compiled by builduser

Features: +acl +iconv +tui
See ":help feature-compile"

   system vimrc file: "$VIM/sysinit.vim"
  fall-back for $VIM: "/usr/share/nvim"

Run :checkhealth for more info

alacritty 0.9.0 (fed349aa)

See if you need other info?

jsulm

@LiZheCN said in [SOLVED] qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in "":

How to solve it?

Set QT_DEBUG_PLUGINS to one before starting the app:

export QT_DEBUG_PLUGINS=1
kate

Post the output.

LiZheCN

@jsulm

The log is too long I put it on this site. Thank you

https://github.com/woshichuanqilz/others/blob/master/log

jsulm

@LiZheCN This looks very strange:

Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin/platforms" ...
loaded library "/home/lizhe/.local/lib/python3.10/site-packages/cv2/qt/plugins/platforms/libqxcb.so"
QObject::moveToThread: Current thread (0x563183178770) is not the object's thread (0x563183184ca0).
Cannot move to target thread (0x563183178770)

All other plug-ins are loaded from /usr/lib/qt/plugins, not /home/lizhe/.local/lib/python3.10/site-packages/cv2/qt/plugins
Do you have /home/lizhe/.local/lib/python3.10 in your PATH?

LiZheCN

@jsulm said in [SOLVED] qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in "":

/home/lizhe/.local/lib/python3.10/site-packages/cv2/qt/plugins

Yes I have this dir

The libxcb.so file I put it here, in case you need it

https://github.com/woshichuanqilz/others/blob/master/libqxcb.so