qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.

shivak3

Hi All,

My system details are:

Operating System: Red Hat Enterprise Linux Server 7.9 (Maipo)
Kernel: Linux 3.10.0-1160.15.2.el7.x86_64
Architecture: x86-64

I see this error when I run mayavi Data Visualizer application after installing PyQT5 5.15.2 version using the pip command like...

[root@RHEL7 ~] pip install PyQt5==5.15.2

When I run mayavi application

[root@RHEL7 ~]$ mayavi2
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" 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: eglfs, minimal, minimalegl, offscreen, vnc, xcb.

Aborted (core dumped)
[root@RHEL7 ~]

I had the mayavi setup under conda environment with PyQt5=5.12.3 version and had no issues with mayavi application.

(base) [root@RHEL7 ~]$ conda list | grep pyqt
pyqt                      5.9.2            py37h05f1152_2  
pyqt5                     5.12.3                   pypi_0    pypi
pyqt5-sip                 12.7.1                   pypi_0    pypi
pyqtwebengine             5.12.1                   pypi_0    pypi

My system environment variables for QT are

[root@RHEL7 ~]$ env | grep QT
QTDIR=/usr/lib64/qt4
QTINC=/usr/lib64/qt4/include
QT_GRAPHICSSYSTEM_CHECKED=1
QT_IM_MODULE=ibus
QTLIB=/usr/lib64/qt4/lib
QT_PLUGIN_PATH=/usr/lib64/kde4/plugins:/usr/lib/kde4/plugins
[root@RHEL7 ~]

Could anyone please help me with this issue. Thank you in advance.

JonB

@shivak3
Hello and welcome.

export QT_DEBUG_PLUGINS=1, and then run your Python program. Look near the end of the diagnostic output for the cause.

There are also an awful lot of topics with this title on this forum you could search for. You may need to install some OS packages. One of them will be your case.

shivak3

@JonB .

Thank you for your reply. I will check it .

shivak3

Hi,

After running export QT_DEBUG_PLUGINS=1, the results are...

QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib64/kde4/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/kde4/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin/anaconda3/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/anaconda3/plugins/platforms/libqeglfs.so"
Found metadata in lib /usr/bin/anaconda3/plugins/platforms/libqeglfs.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "eglfs"
        ]
    },
    "className": "QEglFSIntegrationPlugin",
    "debug": false,
    "version": 329991
}


Got keys from plugin meta data ("eglfs")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/anaconda3/plugins/platforms/libqminimal.so"
Found metadata in lib /usr/bin/anaconda3/plugins/platforms/libqminimal.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimal"
        ]
    },
    "className": "QMinimalIntegrationPlugin",
    "debug": false,
    "version": 329991
}


Got keys from plugin meta data ("minimal")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/anaconda3/plugins/platforms/libqminimalegl.so"
Found metadata in lib /usr/bin/anaconda3/plugins/platforms/libqminimalegl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimalegl"
        ]
    },
    "className": "QMinimalEglIntegrationPlugin",
    "debug": false,
    "version": 329991
}


Got keys from plugin meta data ("minimalegl")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/anaconda3/plugins/platforms/libqoffscreen.so"
Found metadata in lib /usr/bin/anaconda3/plugins/platforms/libqoffscreen.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "offscreen"
        ]
    },
    "className": "QOffscreenIntegrationPlugin",
    "debug": false,
    "version": 329991
}


Got keys from plugin meta data ("offscreen")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/anaconda3/plugins/platforms/libqvnc.so"
Found metadata in lib /usr/bin/anaconda3/plugins/platforms/libqvnc.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "vnc"
        ]
    },
    "className": "QVncIntegrationPlugin",
    "debug": false,
    "version": 329991
}


Got keys from plugin meta data ("vnc")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/anaconda3/plugins/platforms/libqxcb.so"
Found metadata in lib /usr/bin/anaconda3/plugins/platforms/libqxcb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "xcb"
        ]
    },
    "className": "QXcbIntegrationPlugin",
    "debug": false,
    "version": 329991
}


Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin/anaconda3/bin/platforms" ...
Cannot load library /usr/bin/anaconda3/plugins/platforms/libqxcb.so: (/usr/bin/anaconda3/plugins/platforms/../../lib/libQt5XcbQpa.so.5: symbol _ZN11QFontEngine14bitmapForGlyphEj6QFixedRK10QTransform, version Qt_5_PRIVATE_API not defined in file libQt5Gui.so.5 with link time reference)
QLibraryPrivate::loadPlugin failed on "/usr/bin/anaconda3/plugins/platforms/libqxcb.so" : "Cannot load library /usr/bin/anaconda3/plugins/platforms/libqxcb.so: (/usr/bin/anaconda3/plugins/platforms/../../lib/libQt5XcbQpa.so.5: symbol _ZN11QFontEngine14bitmapForGlyphEj6QFixedRK10QTransform, version Qt_5_PRIVATE_API not defined in file libQt5Gui.so.5 with link time reference)"
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" 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: eglfs, minimal, minimalegl, offscreen, vnc, xcb.

Aborted (core dumped)

I tried to install libxcb packages with Yum. But it shows its already installed.

Package libxcb-1.13-1.el7.x86_64 already installed and latest version

Please suggest what best I can do here to fix the issue? TIA.

JoeCFD

@shivak3 said in qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.:

platforms/libqxcb.so

you need this one.
Qt/5.15.2/gcc_64/plugins/platforms/libqxcb.so
and it is not in your search path.
Try to set platform path or plugin path for it. QT_PLUGIN_PATH or QT_QPA_PLATFORM

hskoglund

Hi, if you scroll to the right you'll see the infamous "_ZN11QFontEngine14bitmapForGlyphEj6QFixedRK10QTransform" error, I think it occurs due to a mixup of Python's Qt version and the builtin Qt version.
Google for this error, one solution is here

shivak3

@JoeCFD

Thank you for your reply.

I see no files under plugins folder....

Screenshot 2021-12-20 145616.jpg

shivak3

@hskoglund

Thank you for your reply.

I see many qt related packages. I didn't understand what packages I need to uninstall. Could you please point out for me. Thank you.

**(base) [root@RHEL7 ~]$ pip list | grep qt**
qtconsole                          4.5.5            
sphinxcontrib-qthelp               1.0.2   
         
**(base) [root@RHEL7 ~]$ conda list | grep qt**
pyqt                      5.9.2            py37h05f1152_2  
pyqt5                     5.15.2                   pypi_0    pypi
pyqt5-sip                 12.9.0                   pypi_0    pypi
pyqtwebengine             5.12.1                   pypi_0    pypi
qt                        5.9.7                h5867ecd_1  
qtawesome                 0.6.0                      py_0  
qtconsole                 4.5.5                      py_0  
qtpy                      1.9.0                      py_0  
sphinxcontrib-qthelp      1.0.2                      py_0  

**(base) [root@pbsrhst ~]$ rpm -Qe | grep qt**
rpm: -Qe: unknown option
(base) [root@RHEL7 ~]$ rpm -qa | grep qt
pinentry-qt-0.8.1-17.el7.x86_64
qt5-qtbase-5.9.7-5.el7_9.x86_64
compat-poppler022-qt-0.22.5-4.el7.x86_64
qt5-qtbase-common-5.9.7-5.el7_9.noarch
qt-mysql-4.8.7-9.el7_9.x86_64
qt-4.8.7-9.el7_9.x86_64
ibus-qt-1.3.2-4.el7.x86_64
qt-settings-19-23.12.el7.noarch
qt3-3.3.8b-51.el7.x86_64
polkit-qt-0.103.0-10.el7_0.x86_64
imsettings-qt-1.6.3-11.el7.x86_64
dbusmenu-qt-0.9.2-7.el7.x86_64
poppler-qt-0.26.5-43.el7.1.x86_64
qt-x11-4.8.7-9.el7_9.x86_64

hskoglund

Hi, because you have multiple versions of Qt5 installed on your PC, I think the easiest solution is not to uninstall anything, instead switch to another major version of Qt. You have Qt4 and Qt3 already but they are quite old.
So my suggestion is to install Qt6, then you will only have one version of it and that error ""_ZN11QFontEngine14bitmapForGlyphEj6QFixedRK10QTransform" will go away :-)