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Running Qt Applications with Errors

We found that there is a general issue when we run some qt-based applications on Chrome OS Linux distro, Debian 10.

The following error messages comes up when we try to launch some qt applications:

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, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.

Aborted (core dumped)

Proposed Solutions

Solution 1 is simpler than solution 2, but solution 1 has some drawbacks on some qt applications.

You may try solution 1 first. If solution does not work for you, you may try solution 2.

So far, either of the following solutions solve the issue we mentioned above.

Solution 1

try to run the following command first and see if it works for you:

export QT_QPA_PLATFORM=wayland

If your application works after running this command, you may want to make it more persistant by running the following commands:

echo "export QT_QPA_PLATFORM=wayland" >> ~/.bashrc

sudo echo "Environment='QT_QPA_PLATFORM=wayland'" >> /etc/systemd/user/cros-garcon.service.d/cros-garcon-override.conf

The above solution works with some applications. HOWEVER, some other applications have issues with chrome os wayland compositor that:

  1. main window open and closes repetitively

  2. input method "fcitx" breaks

  3. Errors message comes up on terminal indicates that there is possibly a bug in chrome os wayland compositor, e.g. :

qt.qpa.wayland: Ignoring unexpected wl_surface.enter received for output with id: 7 screen name: "Screen5" screen model: "202B" This is most likely a bug in the compositor.

If one of these problems happen with your application, you may try the following solution.

Before you continue:

If you changed the varaible of QT_QPA_PLATFORM to wayland, you may want to change it back to xcb:

echo "export QT_QPA_PLATFORM=xcb" >> ~/.bashrc

sudo echo "Environment='QT_QPA_PLATFORM=xcb'" >> /etc/systemd/user/cros-garcon.service.d/cros-garcon-override.conf

Solution 2

Simply run the following command to fix the issue:

sudo ln -s /usr/lib/x86_64-linux-gnu/libxcb-util.so.0 /usr/lib/x86_64-linux-gnu/libxcb-util.so.1

Explanation about this solution (if you are interested):

You may be interested how we comes up with the solution above. We briefly describe below:

We ran a command:

export QT_DEBUG_PLUGINS=1

Then, we run a qt application which does not work with solution 1 and get the following error message:

...
Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin/platforms" ...
Cannot load library /home/eliranwong/UniqueBible/venv/lib/python3.7/site-packages/PySide2/Qt/plugins/platforms/libqxcb.so: (libxcb-util.so.1: cannot open shared object file: No such file or directory)
QLibraryPrivate::loadPlugin failed on "/home/eliranwong/UniqueBible/venv/lib/python3.7/site-packages/PySide2/Qt/plugins/platforms/libqxcb.so" : "Cannot load library /home/eliranwong/UniqueBible/venv/lib/python3.7/site-packages/PySide2/Qt/plugins/platforms/libqxcb.so: (libxcb-util.so.1: cannot open shared object file: No such file or directory)"
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, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.

Aborted (core dumped)

Then, we check if we have "libxcb-util" installed:

mlocate libxcb-util

We get the following result:

/usr/lib/x86_64-linux-gnu/libxcb-util.so.0
/usr/lib/x86_64-linux-gnu/libxcb-util.so.0.0.0

It appears to us that libxcb-util.so is installed but version does not match. So, we searched and see what version of libxcb-util is available:

apt search libxcb-util

However, only version 0 is available at the moment of writing:

libxcb-util0/stable,now 0.3.8-3+b2 amd64 [installed]

Therefore, we comes up with a solution to create a soft link suggested above.

So far, all tested applications work with either one of the solutions mentioned above.