I wrote application for linux which uses Qt5.
But when I am trying to launch it on the linux without Qt SDK installed, the output in console is:
Failed to load platform plugin "xcb". Available platforms are:
How can I fix this? May be I need to copy some plugin file?
When I use ubuntu with Qt5 installed, but I rename Qt directory, the same problem occurs. So, it uses some file from Qt directory...
UPDATE:
when I create in the app dir "platforms" folder with the file libqxcb.so, the app still doesnot start, but the error message changes:
Failed to load platform plugin "xcb". Available platforms are:
xcb
How can this happen? How can platform plugin be available but can't be loaded?
Use ldd (man ldd) to show shared library dependencies. Running this on libqxcb.so
.../platforms$ ldd libqxcb.so
shows that xcb depends on libQt5DBus.so.5 in addition to libQt5Core.so.5 and libQt5Gui.so.5 (and many other system libs). Add libQt5DBus.so.5 to your collection of shared libs and you should be ready to move on.
As was posted earlier, you need to make sure you install the platform plugins when you deploy your application. Depending on how you want to deploy things, there are two methods to tell your application where the platform plugins (e.g. platforms/plugins/libqxcb.so) are at runtime which may work for you.
The first is to export the path to the directory through the QT_QPA_PLATFORM_PLUGIN_PATH variable.
QT_QPA_PLATFORM_PLUGIN_PATH=path/to/plugins ./my_qt_app
or
export QT_QPA_PLATFORM_PLUGIN_PATH=path/to/plugins
./my_qt_app
The other option, which I prefer is to create a qt.conf file in the same directory as your executable. The contents of which would be:
[Paths]
Plugins=/path/to/plugins
More information regarding this can be found here and at using qt.conf
I tried to start my binary, compiled with Qt 5.7, on Ubuntu 16.04 LTS where Qt 5.5 is preinstalled. It didn't work.
At first, I inspected the binary itself with ldd as was suggested here, and satisfied all "not found" dependencies. Then this notorious This application failed to start because it could not find or load the Qt platform plugin "xcb" error was thrown.
How to resolve this in Linux
Firstly you should create platforms directory where your binary is, because it is the place where Qt looks for XCB library. Copy libqxcb.so there. I wonder why authors of other answers didn't mention this.
Then you may want to run your binary with QT_DEBUG_PLUGINS=1 environment variable set to check which dependencies of libqxcb.so are not satisfied. (You may also use ldd for this as suggested in the accepted answer).
The command output may look like this:
me#xerus:/media/sf_Qt/Package$ LD_LIBRARY_PATH=. QT_DEBUG_PLUGINS=1 ./Binary
QFactoryLoader::QFactoryLoader() checking directory path "/media/sf_Qt/Package/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/media/sf_Qt/Package/platforms/libqxcb.so"
Found metadata in lib /media/sf_Qt/Package/platforms/libqxcb.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"xcb"
]
},
"className": "QXcbIntegrationPlugin",
"debug": false,
"version": 329472
}
Got keys from plugin meta data ("xcb")
loaded library "/media/sf_Qt/Package/platforms/libqxcb.so"
QLibraryPrivate::loadPlugin failed on "/media/sf_Qt/Package/platforms/libqxcb.so" : "Cannot load library /media/sf_Qt/Package/platforms/libqxcb.so: (/usr/lib/x86_64-linux-gnu/libQt5DBus.so.5: version `Qt_5' not found (required by ./libQt5XcbQpa.so.5))"
This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".
Available platform plugins are: xcb.
Reinstalling the application may fix this problem.
Aborted (core dumped)
Note the failing libQt5DBus.so.5 library. Copy it to your libraries path, in my case it was the same directory where my binary is (hence LD_LIBRARY_PATH=.). Repeat this process until all dependencies are satisfied.
P.S. thanks to the author of this answer for QT_DEBUG_PLUGINS=1.
I tried the main parts of each answer, to no avail. What finally fixed it for me was to export the following environment variables:
LD_LIBRARY_PATH=/usr/local/lib:~/Qt/5.9.1/gcc_64/lib
QT_QPA_PLATFORM_PLUGIN_PATH=~/Qt/5.9.1/gcc_64/plugins/
Ubuntu 16.04 64bit.
I got the problem for apparently no reasons. The night before I watched a movie on my VideoLan instance, that night I would like to watch another one with VideoLan. VLC just didn't want to run because of the error into the question.
I google a bit and I found the solution it solved my problem: from now on, VLC is runnable just like before. The solution is this comand:
sudo ln -sf /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/ /usr/bin/
I am not able to explain what are its consequencies, but I know it creates some missing symbolic link.
Since version 5, Qt uses a platform abstraction system (QPA) to abstract from the underlying platform.
The implementation for each platform is provided by plugins. For X11 it is the XCB plugin. See Qt for X11 requirements for more information about the dependencies.
There might be many causes to this problem. The key is to use
export QT_DEBUG_PLUGINS=1
before you run your Qt application. Then, inspect the output, which will point you to the direction of the error. In my case it was:
Cannot load library /opt/nao/plugins/platforms/libqxcb.so: (/opt/nao/bin/../lib/libz.so.1: version `ZLIB_1.2.9' not found (required by /usr/lib/x86_64-linux-gnu/libpng16.so.16))
But that is solved in different threads. See for instance https://stackoverflow.com/a/50097275/2408964.
Probably this information will help. I was on Ubuntu 18.04 and when I tried to install Krita, using the ppa method, I got this error:
This application failed to start because it could not find or load the Qt platform plugin "xcb" in "".
Available platform plugins are: linuxfb, minimal, minimalegl, offscreen, wayland-egl, wayland, xcb.
Reinstalling the application may fix this problem.
Aborted
I tried all the solutions that I found in this thread and other webs without any success.
Finally, I found a post where the author mention that is possible to activate the debugging tool of qt5 using this simple command:
export QT_DEBUG_PLUGINS=1
After adding this command I run again krita I got the same error, however this time I knew the cause of that error.
libxcb-xinerama.so.0: cannot open shared object file: No such file or directory.
This error prevents to the "xcb" to load properly. So, the solution will be install the `libxcb-xinerama.so.0" right? However, when I run the command:
sudo apt install libxcb-xinerama
The lib was already installed. Now what Teo? Well, then I used an old trick :) Yeah, that one --reinstall
sudo apt install --reinstall libxcb-xinerama
TLDR: This last command solved my problem.
I ran into a very similar problem with the same error message. First, debug some by turning on the Qt Debug printer with the command line command:
export QT_DEBUG_PLUGINS=1
and rerun the application. For me this revealed the following:
"Cannot load library /home/.../miniconda3/lib/python3.7/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so: (libxkbcommon-x11.so.0: cannot open shared object file: No such file or directory)"
"Cannot load library /home/.../miniconda3/lib/python3.7/site-packages/PyQt5/Qt/plugins/platforms/libqxcb.so: (libxkbcommon-x11.so.0: cannot open shared object file: No such file or directory)"
Indeed, I was missing libxkbcommon-x11.so.0 and libxkbcommon-x11.so.0. Next, check your architecture using dpkg from the linux command line. (For me, the command "arch" gave a different and unhelpful result)
dpkg --print-architecture #result for me: amd64
I then googled "libxkbcommon-x11.so.0 ubuntu 18.04 amd64", and likewise for libxkbcommon-x11.so.0, which yields those packages on packages.ubuntu.com. That told me, in retrospect unsurprisingly, I'm missing packages called libxkbcommon-x11-0 and libxkbcommon0, and that installing those packages will include the needed files, but the dev versions will not. Then the solution:
sudo apt-get update
sudo apt-get install libxkbcommon0
sudo apt-get install libxkbcommon-x11-0
So, I spent about a day trying to figure out what was the issue; tried all the proposed solutions, but none of that worked like installing xcb libs or exporting Qt plugins folder. The solution that suggested to use QT_DEBUG_PLUGINS=1 to debug the issue didn't provide me a direct insight like in the answer - instead I was getting something about unresolved symbols within Qt5Core.
That gave me a hint, though: what if it's trying to use different files from different Qt installations? On my machine I had standard version installed in /home/username/Qt/ and some local builds within my project that I compiled by myself (I have other custom built kits as well in other locations). Whenever I tried to use any of the kits (installed by Qt maintenance tool or built by myself), I would get an "xcb error".
The solution was simple: provide the Qt path through CMAKE_PREFIX_PATH and not though Qt5_DIR as I did, and it solved the problem. Example:
cmake .. -DCMAKE_PREFIX_PATH=/home/username/Qt/5.11.1/gcc_64
I faced the same problem when after installing Viber. It had all required qt libraries in /opt/viber/plugins/.
I checked dependencies of /opt/viber/plugins/platforms/libqxcb.so and found missing dependencies. They were libxcb-render.so.0, libxcb-image.so.0, libxcb-icccm.so.4, libxcb-xkb.so.1
So I resolved my issue by installing missing packages with this libraries:
apt-get install libxcb-xkb1 libxcb-icccm4 libxcb-image0 libxcb-render-util0
I like the solution with qt.conf.
Put qt.conf near to the executable with next lines:
[Paths]
Prefix = /path/to/qtbase
And it works like a charm :^)
For a working example:
[Paths]
Prefix = /home/user/SDKS/Qt/5.6.2/5.6/gcc_64/
The documentation on this is here: https://doc.qt.io/qt-5/qt-conf.html
All you need to do is
pip uninstall PyQt5
and
conda install pyqt
Most of the problem of pyqt can be fixed by this simplest solution.
In my case, I needed to deploy two Qt apps on an Ubuntu virtualbox guest. One was command-line ("app"), the other GUI_based ("app_GUI").
I used "ldd app" to find out what the required libs are, and copied them
to the Ubuntu guest.
While the command-line executable "app" worked ok, the GUI-based executable crashed, giving
the "Failed to load platform plugin "xcb" error. I checked ldd for libxcb.so, but this too had no missing dependencies.
The problem seemed to be that while I did copy all the right libraries I accidentally had copied also libraries that were already present at the guest system.. meaning that (a) they were unnecessary to copy them in the first place and (b) worse, copying them produced incompatibilities between the install libraries.
Worse still, they were undetectable by ldd like I said..
The solution? Make sure that you copy libraries shown as missing by ldd and absolutely no extra libraries.
In my case missing header files were the reason libxcb was not built by Qt. Installing them according to https://wiki.qt.io/Building_Qt_5_from_Git#Linux.2FX11 resolved the issue:
yum install libxcb libxcb-devel xcb-util xcb-util-devel mesa-libGL-devel libxkbcommon-devel
Folks trying to get this started on Ubuntu 20.04 please try to run this and see if this solves the problem. This worked for me
sudo apt-get update -y
sudo apt-get install -y libxcb-xinerama0
I link all Qt stuff statically to the generic Linux builds of my open source projects. It makes life a bit easier. You just need to build static versions of Qt libraries first. Of course this cannot be applied to closed source software due to licensing issues. The deployment of Qt5 apps on Linux is currently a bit problematic, because Ubuntu 12.04, for example, doesn't have Qt5 libraries in the package repositories.
I had this problem, and on a hunch I removed the Qt Configs from my environment. I.e.,
rm -rf ~/.config/Qt*
Then I started qtcreator and it reconfigured itself with the existing state of the machine. It no longer remembered where my projects were, but that just meant I had to browse to them "for the first time" again.
But more importantly it built itself a coherent set of library paths, so I could rebuild and run my project executables again without the xcb or qxcb libraries going missing.
I faced the same situation, but on a Ubuntu 20.04 VM.
TL;DR: Check file permissions.
What I did:
I copied the Qt libs required to /usr/local/lib/x86_64-linux-gnu/ and added it to LD_LIBRARY_PATH
I copied the platforms folder from Qt to my application directory and added it to QT_PLUGIN_PATH
I ran ldd on the executable and in the offending libqxcb.so (ldd libqxcb.so), and it complains about some dependencies although ldconfig listed them as found.
linux-vdso.so.1 (0x00007ffee19af000)
libQt5XcbQpa.so.5 => not found
libfontconfig.so.1 => /lib/x86_64-linux-gnu/libfontconfig.so.1 (0x00007f7cb18fb000)
libfreetype.so.6 => /lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007f7cb183c000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f7cb1820000)
libQt5Gui.so.5 => /usr/local/lib/x86_64-linux-gnu/libQt5Gui.so.5 (0x00007f7cb0fd4000)
libQt5DBus.so.5 => not found
I used export QT_DEBUG_PLUGINS=1 for further info. It complains about missing files, although they are there.
What I found:
For some reason, when copying to the VM through the shared folder the files permissions were not the correct ones.
Thus, I ran: sudo chmod 775 * on the libs and voilà.
I solved the issue through this https://github.com/NVlabs/instant-ngp/discussions/300
pip uninstall opencv-python
pip install opencv-python-headless
This seems to have been a problem with the cv2 Python package and how it loops in Qt
sudo ln -sf /usr/lib/...."adapt-it"..../qt5/plugins/platforms/ /usr/bin/
It creates the symbolic link it's missed. Good for QT ! Good for VLC !!
I am building the Visual Studio Code from the source checked out from the git repository:
git clone https://github.com/microsoft/vscode
I am building using:
export NODE_OPTIONS=--max_old_space_size=2048
./scripts/npm.sh install --arch=armhf
./scripts/code.sh
I am using node 10.16.3 on a Raspberry PI 4, using Raspbian buster
There were no errors during build.
The installation downloads a precompiled version of electron on the first run.
However each time I try and run code, it starts but with an error:
[storage state.vscdb] open(): Unable to open DB due to Error: Cannot find module '../build/Release/sqlite
If I look in node_modules/vscode-sqlite3/build/Release/
I can see:
sqlite3.a
sqlite.a
It is unclear to me why electron/vscode cannot find this library. I would be greatful for any pointers on how to tell the runtime where to look for the modules.
On inspecting the build scripts and after many painful experiments, I've found and solved the 2 problems leading to this error.
The fact that .a static libraries are left behind hinted that some settings in the binding.gyp, config.gpy and/or makefiles are wrong, as Native Node Modules are normally dynamic libraries with an .node extension. One conditional line in the binding.gyp file under vscode-sqlite3 seems to the the culprit:
...
["target_arch=='arm'", {"type": "static_library"}]
...
Disable that line (by removing it or changing 'arm' to something else) and then run:
node-gyp configure
to regenerate the config.gpy file(s) under the build directory. Then build the module with:
node-gyp build
A sqlite.node will be generated in build/Release.
Unfortunately, the latest electron ABI version rarely matches that of the Node.js version. In my configuration, the electron ABI version is 72 (v6.0.12) but the latest stable Node version is for ABI 64. Therefore we have to do an electron-rebuild to update the sqlite.node to match the electron version.
To do this, you would have to first install electron-rebuild (yarn add electron-rebuild) then run electron-rebuild by giving supplying explicitly the version number of the electron binary that vscode downloaded:
electron-rebuild -v 6.0.12 -m /home/dev/vscode -o vscode-sqlite3
Of course you would have to state the version number of your particular version of electron you are building for.
(Please look up electron-rebuild --help for the meaning of the options. It takes a while to rebuild the binary module...)
The resulting sqlite.node can then be moved into the build/Release/. directory under the vscode project directory. Voila, we have a working latest version VS-Code for Raspbian!
Just installed QT and trying to build a QT project from inside the QTcreator using Cmake instead of Qmake.
I get the following error:
Starting to parse CMake project, using: "DCMAKE_BUILD_TYPE:STRING=Debug",
"-DCMAKE_CXX_COMPILER:STRING=",
"-DCMAKE_C_COMPILER:STRING=",
"DCMAKE_PREFIX_PATH:STRING=C:/Qt/5.13.1/msvc2015_64",
"DQT_QMAKE_EXECUTABLE:STRING=C:/Qt/5.13.1/msvc2015_64/bin/qmake.exe".
The CXX compiler identification is unknown
CMake Error at CMakeLists.txt:3 (project):
The CMAKE_CXX_COMPILER:
cl
is not a full path and was not found in the PATH.
To use the JOM generator with Visual C++, cmake must be run from a shell
that can use the compiler cl from the command line. This environment is
unable to invoke the cl compiler. To fix this problem, run cmake from the
Visual Studio Command Prompt (vcvarsall.bat).
Tell CMake where to find the compiler by setting either the environment
variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path
to the compiler, or to the compiler name if it is in the PATH.
Configuring incomplete, errors occurred!
See also "C:/Users/tany/AppData/Local/Temp/QtCreator-pKrFgC/qtc-cmake-DqmsxZqd/CMakeFiles/CMakeOutput.log".
See also "C:/Users/tany/AppData/Local/Temp/QtCreator-pKrFgC/qtc-cmake-DqmsxZqd/CMakeFiles/CMakeError.log".
CMake Deprecation Warning:
The 'cmake-server(7)' is deprecated. Please port clients to use the
'cmake-file-api(7)' instead.
CMake Project parsing failed.
Now if I use the Cmake-GUI instead, I can configure and generate the project files successfully, after supplying the environment variable CMAKE_PREFIX_PATH.
But I can't get this to work from inside the QTcreator.
Anyone has any experience with using Cmake with QTcreator then please help.
Thank you!
The error message says that your C++ compiler Visual Studio 2015 (64 bits) could not be located. Maybe when you run cmake-gui it finds another C++ compiler like mingw?
In Qtcreator's settings dialog you have a tab showing the detected compilers, and another one with the available kits.
It seems that QtCreator is using a deprecated version of cmake. Update QtCreator to a new (unreleased, as writing this comment, version 4.10.0 is broken) or downgrade cmake to choco.exe install cmake --version 3.11 --force (a newer version might work).
Please also make sure to install jom (as this is the default for QtCreator/CMake on windows).
choco.exe install jom (how can I tell it to use make?)
The deprecation warning is harmless. CMake deprecated the cmake-server and provides a new API for the same purpose now. Qt Creator will support that from 4.11.
The error tells you, that CMake is unable find the cl compiler. cl.exe comes with Visual Studio. Make sure you mark C++ there during the installation process. It is not installed by default anymore.
Alternatively install the MinGW tool chain from the Qt installer. In Qt context it is easier to use than the Visual Studio tool chain.
I am trying to install kde-connect following this.
Although my kubuntu version is 14.04, I wanted to compile them so that I can have the latest version. But when I followed the instructions to compile, i get the following error.
-- Found Qt-Version 5.2.1 (using /usr/bin/qmake)
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
QT_QT_INCLUDE_DIR
used as include directory in directory /home/vinaychandra/Downloads/t/CMakeFiles/CMakeTmp
CMake Error: Internal CMake error, TryCompile configure of cmake failed
CMake Error at /usr/share/kde4/apps/cmake/modules/FindKDE4Internal.cmake:1311 (message):
Unable to compile a basic Qt application. Qt has not been found correctly.
Call Stack (most recent call first):
/usr/share/cmake-2.8/Modules/FindKDE4.cmake:95 (find_package)
CMakeLists.txt:7 (find_package)
Please point out how to correct this.
I have tried giving -DQT_QT_INCLUDE_DIR=/usr/share/qt4/
then it tells that You must build your code with position independent code if Qt was built with -reduce-relocations.
Your cmake by default uses a different QT version.
So, you must explicitly tell him which version of QT he have to use for this job.
This one
-DQT_QT_INCLUDE_DIR=/usr/share/qt4/
Is wrong because you mustn't give QT position explicitly.
All you need is to use the right qmake.
So, give'em this flag and you'll be happy!
-DQT_QMAKE_EXECUTABLE=/usr/bin/qmake-qt4
Since most of kde applications are not ported to Qt5, you need Qt4.x for building kdeconnect(don't know x, mine is 4.8.6).
Also Qt4 installer is not available (I think !), so you have to build it also from source. Building Qt4 is quite easy, just download the source and run the usual commands.
After building it, it qmake name will be qmake-qt4 in /usr/bin.
So for building kdeconnect, first run its cmake, then a Cmaketextcache.txt file will form.
In that change the path of qmake (i.e somewhere written /usr/bin/qmake to /usr/bin/qmake-qt4) and also the path of qt include dir to (I think /usr/include/qt5 to /usr/include/qt4), and run the cmake again.
If some packages are missing, then you have to install it.
But with the above changes, you will get a make file to install it.
Unfortunately, the cited documentation is lagging behind the current state of kdeconnect. I ran into similar problems but I managed to solve them by installing the following required packages from the Kubuntu repositories:
sshfs
libfakekey-dev
libxtst-dev
libqca2-dev
libqjson-dev
I trust these are all of them. I installed kdeconnect from the latest git commit and it seems to run fine.
This answer comes a bit late, but this is the first Google search result for the question. In systems with qtchooser (Kubuntu, Ubuntu at least), this can be fixed by running first:
export QT_SELECT=qt4
This makes all of the Qt build tools to default to the Qt4 version instead of Qt5. You can check which Qt version is active by running:
qmake --version
Try kde connect install on ubuntu: https://fazlerabbi37.github.io/blogs/install_kde_connect_in_ubuntu_18.04.html
(in 18.04 & 19.04 it works with simple sudo apt install kdeconnect
Install kde connect on android device (google play store is where I installed from)
Invoke kde connect from desktop
Invoke kde connect from android and search device.
Your ubuntu will be found / initiating a search from desktop results in android phone pulled up for pairing
Accept pairing request
Provide access to folders
Try clicking on a video/image file for transfer
I could see the new file transferring in /Downloads folder of desktop
allowing/disallowing desktop to access sms, notifications etc are now a choice
Note: Pl treat this with pinch of salt. This appears very simple, effective for a main reason it worked for me in no time.