(Linux) qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
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I'm trying to run XP-Pen pentablet drivers on my system-- they launch just fine under my normal user, but because they are drivers I need to run them as root, which gives me the following error:
sleepy@magi ~/Programs/Pentablet/Linux_Pentablet_V1.2.13.1 $ sudo QT_DEBUG_PLUGINS=1 ./Pentablet_Driver QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib64/qt5/plugins/platforms" ... QFactoryLoader::QFactoryLoader() looking at "/usr/lib64/qt5/plugins/platforms/KWinQpaPlugin.so" Found metadata in lib /usr/lib64/qt5/plugins/platforms/KWinQpaPlugin.so, metadata= { "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3", "MetaData": { "Keys": [ "wayland-org.kde.kwin.qpa" ] }, "archreq": 2, "className": "KWinIntegrationPlugin", "debug": false, "version": 331520 } Got keys from plugin meta data ("wayland-org.kde.kwin.qpa") QFactoryLoader::QFactoryLoader() looking at "/usr/lib64/qt5/plugins/platforms/libqminimal.so" Found metadata in lib /usr/lib64/qt5/plugins/platforms/libqminimal.so, metadata= { "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3", "MetaData": { "Keys": [ "minimal" ] }, "archreq": 2, "className": "QMinimalIntegrationPlugin", "debug": false, "version": 331520 } Got keys from plugin meta data ("minimal") QFactoryLoader::QFactoryLoader() looking at "/usr/lib64/qt5/plugins/platforms/libqoffscreen.so" Found metadata in lib /usr/lib64/qt5/plugins/platforms/libqoffscreen.so, metadata= { "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3", "MetaData": { "Keys": [ "offscreen" ] }, "archreq": 2, "className": "QOffscreenIntegrationPlugin", "debug": false, "version": 331520 } Got keys from plugin meta data ("offscreen") QFactoryLoader::QFactoryLoader() looking at "/usr/lib64/qt5/plugins/platforms/libqwayland-egl.so" Found metadata in lib /usr/lib64/qt5/plugins/platforms/libqwayland-egl.so, metadata= { "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3", "MetaData": { "Keys": [ "wayland-egl" ] }, "archreq": 2, "className": "QWaylandEglPlatformIntegrationPlugin", "debug": false, "version": 331520 } Got keys from plugin meta data ("wayland-egl") QFactoryLoader::QFactoryLoader() looking at "/usr/lib64/qt5/plugins/platforms/libqwayland-generic.so" Found metadata in lib /usr/lib64/qt5/plugins/platforms/libqwayland-generic.so, metadata= { "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3", "MetaData": { "Keys": [ "wayland" ] }, "archreq": 2, "className": "QWaylandIntegrationPlugin", "debug": false, "version": 331520 } Got keys from plugin meta data ("wayland") QFactoryLoader::QFactoryLoader() looking at "/usr/lib64/qt5/plugins/platforms/libqwayland-xcomposite-egl.so" Found metadata in lib /usr/lib64/qt5/plugins/platforms/libqwayland-xcomposite-egl.so, metadata= { "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3", "MetaData": { "Keys": [ "wayland-xcomposite-egl" ] }, "archreq": 2, "className": "QWaylandXCompositeEglPlatformIntegrationPlugin", "debug": false, "version": 331520 } Got keys from plugin meta data ("wayland-xcomposite-egl") QFactoryLoader::QFactoryLoader() looking at "/usr/lib64/qt5/plugins/platforms/libqwayland-xcomposite-glx.so" Found metadata in lib /usr/lib64/qt5/plugins/platforms/libqwayland-xcomposite-glx.so, metadata= { "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3", "MetaData": { "Keys": [ "wayland-xcomposite-glx" ] }, "archreq": 2, "className": "QWaylandXCompositeGlxPlatformIntegrationPlugin", "debug": false, "version": 331520 } Got keys from plugin meta data ("wayland-xcomposite-glx") QFactoryLoader::QFactoryLoader() looking at "/usr/lib64/qt5/plugins/platforms/libqxcb.so" Found metadata in lib /usr/lib64/qt5/plugins/platforms/libqxcb.so, metadata= { "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3", "MetaData": { "Keys": [ "xcb" ] }, "archreq": 2, "className": "QXcbIntegrationPlugin", "debug": false, "version": 331520 } Got keys from plugin meta data ("xcb") QFactoryLoader::QFactoryLoader() checking directory path "/home/sleepy/Programs/Pentablet/Linux_Pentablet_V1.2.13.1/platforms" ... QFactoryLoader::QFactoryLoader() looking at "/home/sleepy/Programs/Pentablet/Linux_Pentablet_V1.2.13.1/platforms/libqxcb.so" Found metadata in lib /home/sleepy/Programs/Pentablet/Linux_Pentablet_V1.2.13.1/platforms/libqxcb.so, metadata= { "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3", "MetaData": { "Keys": [ "xcb" ] }, "className": "QXcbIntegrationPlugin", "debug": false, "version": 330241 } Got keys from plugin meta data ("xcb") loaded library "/usr/lib64/qt5/plugins/platforms/libqxcb.so" No protocol specified qt.qpa.xcb: could not connect to display :0 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: wayland-org.kde.kwin.qpa, minimal, offscreen, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb. Aborted
I'm using Gentoo and I have xcb installed:
sleepy@magi ~/Programs/Pentablet/Linux_Pentablet_V1.2.13.1 $ eix xcb * dev-perl/X11-XCB Available versions: 0.170.0-r1^t {test} Homepage: https://metacpan.org/release/X11-XCB Description: Perl bindings for libxcb [I] x11-base/xcb-proto Available versions: 1.14-r1 {ABI_MIPS="n32 n64 o32" ABI_RISCV="lp64 lp64d" ABI_S390="32 64" ABI_X86="32 64 x32" PYTHON_TARGETS="python3_6 python3_7 python3_8"} Installed versions: 1.14-r1(08:32:13 PM 05/08/2020)(ABI_MIPS="-n32 -n64 -o32" ABI_RISCV="-lp64 -lp64d" ABI_S390="-32 -64" ABI_X86="32 64 -x32" PYTHON_TARGETS="python3_7 python3_8 -python3_6") Homepage: https://xcb.freedesktop.org/ https://gitlab.freedesktop.org/xorg/proto/xcbproto Description: X C-language Bindings protocol headers [I] x11-libs/libxcb Available versions: 1.14(0/1.12)^t {doc selinux static-libs test +xkb ABI_MIPS="n32 n64 o32" ABI_RISCV="lp64 lp64d" ABI_S390="32 64" ABI_X86="32 64 x32"} Installed versions: 1.14(0/1.12)^t(08:32:42 PM 05/08/2020)(xkb -doc -selinux -static-libs -test ABI_MIPS="-n32 -n64 -o32" ABI_RISCV="-lp64 -lp64d" ABI_S390="-32 -64" ABI_X86="32 64 -x32") Homepage: https://xcb.freedesktop.org/ https://gitlab.freedesktop.org/xorg/lib/libxcb Description: X C-language Bindings library [I] x11-libs/xcb-util Available versions: 0.4.0-r1^t {doc static-libs test ABI_MIPS="n32 n64 o32" ABI_RISCV="lp64 lp64d" ABI_S390="32 64" ABI_X86="32 64 x32"} Installed versions: 0.4.0-r1^t(08:07:25 AM 05/22/2020)(-doc -static-libs -test ABI_MIPS="-n32 -n64 -o32" ABI_RISCV="-lp64 -lp64d" ABI_S390="-32 -64" ABI_X86="32 64 -x32") Homepage: https://xcb.freedesktop.org/ https://gitlab.freedesktop.org/xorg/lib/libxcb-util Description: X C-language Bindings sample implementations [I] x11-libs/xcb-util-cursor Available versions: 0.1.3-r2^t {doc static-libs test ABI_MIPS="n32 n64 o32" ABI_RISCV="lp64 lp64d" ABI_S390="32 64" ABI_X86="32 64 x32"} Installed versions: 0.1.3-r2^t(08:07:58 AM 05/22/2020)(-doc -static-libs -test ABI_MIPS="-n32 -n64 -o32" ABI_RISCV="-lp64 -lp64d" ABI_S390="-32 -64" ABI_X86="32 64 -x32") Homepage: https://xcb.freedesktop.org/ https://gitlab.freedesktop.org/xorg/lib/libxcb-cursor Description: X C-language Bindings sample implementations [I] x11-libs/xcb-util-image Available versions: 0.4.0-r1^t {doc static-libs test ABI_MIPS="n32 n64 o32" ABI_RISCV="lp64 lp64d" ABI_S390="32 64" ABI_X86="32 64 x32"} Installed versions: 0.4.0-r1^t(08:07:41 AM 05/22/2020)(-doc -static-libs -test ABI_MIPS="-n32 -n64 -o32" ABI_RISCV="-lp64 -lp64d" ABI_S390="-32 -64" ABI_X86="32 64 -x32") Homepage: https://xcb.freedesktop.org/ https://gitlab.freedesktop.org/xorg/lib/libxcb-image Description: X C-language Bindings sample implementations [I] x11-libs/xcb-util-keysyms Available versions: 0.4.0-r1^t {doc static-libs test ABI_MIPS="n32 n64 o32" ABI_RISCV="lp64 lp64d" ABI_S390="32 64" ABI_X86="32 64 x32"} Installed versions: 0.4.0-r1^t(08:03:51 AM 05/22/2020)(-doc -static-libs -test ABI_MIPS="-n32 -n64 -o32" ABI_RISCV="-lp64 -lp64d" ABI_S390="-32 -64" ABI_X86="32 64 -x32") Homepage: https://xcb.freedesktop.org/ https://gitlab.freedesktop.org/xorg/lib/libxcb-keysyms Description: X C-language Bindings sample implementations [I] x11-libs/xcb-util-renderutil Available versions: 0.3.9-r2^t {doc static-libs test ABI_MIPS="n32 n64 o32" ABI_RISCV="lp64 lp64d" ABI_S390="32 64" ABI_X86="32 64 x32"} Installed versions: 0.3.9-r2^t(08:04:24 AM 05/22/2020)(-doc -static-libs -test ABI_MIPS="-n32 -n64 -o32" ABI_RISCV="-lp64 -lp64d" ABI_S390="-32 -64" ABI_X86="32 64 -x32") Homepage: https://xcb.freedesktop.org/ https://gitlab.freedesktop.org/xorg/lib/libxcb-render-util Description: X C-language Bindings sample implementations [I] x11-libs/xcb-util-wm Available versions: 0.4.1-r2^t {doc static-libs test ABI_MIPS="n32 n64 o32" ABI_RISCV="lp64 lp64d" ABI_S390="32 64" ABI_X86="32 64 x32"} Installed versions: 0.4.1-r2^t(08:04:09 AM 05/22/2020)(-doc -static-libs -test ABI_MIPS="-n32 -n64 -o32" ABI_RISCV="-lp64 -lp64d" ABI_S390="-32 -64" ABI_X86="32 64 -x32") Homepage: https://xcb.freedesktop.org/ https://gitlab.freedesktop.org/xorg/lib/libxcb-wm Description: X C-language Bindings sample implementations * x11-libs/xcb-util-xrm Available versions: 1.3^t {doc static-libs test ABI_MIPS="n32 n64 o32" ABI_RISCV="lp64 lp64d" ABI_S390="32 64" ABI_X86="32 64 x32"} Homepage: https://xcb.freedesktop.org/ Description: X C-language Bindings sample implementations [I] x11-misc/xcb Available versions: 2.4-r1 {motif} Installed versions: 2.4-r1(05:04:39 PM 08/29/2020)(-motif) Homepage: http://oldhome.schmorp.de/marc/xcb.html Description: Marc Lehmann's improved X Cut Buffers Found 11 matches
Running the application under polkit does not fix the issue. How can I fix this?
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Hi, I think this is not a really a Qt question, because you get the error "No protocol specified, qt.qpa.xcb: could not connect to display :0"
Try copying your .Xauthority file into /root, say like this:
sudo cp ~/.Xauthority /root
Otherwise, there are lots of hits googling that error, here is one that might help:
https://unix.stackexchange.com/questions/118811/why-cant-i-run-gui-apps-from-root-no-protocol-specified -
@hskoglund said in (Linux) qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.:
Hi, I think this is not a really a Qt question, because you get the error "No protocol specified, qt.qpa.xcb: could not connect to display :0"
Try copying your .Xauthority file into /root, say like this:
sudo cp ~/.Xauthority /root
Otherwise, there are lots of hits googling that error, here is one that might help:
https://unix.stackexchange.com/questions/118811/why-cant-i-run-gui-apps-from-root-no-protocol-specifiedAh yup, that fixed it. Thank you!
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