If dcaspt2-input-generator is installed and started on a machine with a GUI environment in X11, the following error may occurred.
$ dcaspt2_input_generator
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.
- This error is caused by not installing the libqxcb.so dependency library, described in detail in https://doc.qt.io/qt-5/linux-requirements.html .
The following steps should solve the problem
1. Install all the packages listed in https://doc.qt.io/qt-5/linux-requirements.html .
2. If 1 does not solve the problem, find and install further required libraries.
2.1. Run QT_DEBUG_PLUGINS=1 dcaspt2_input_generator. You will get the following output
```out
...
Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/home/noda/.pyenv/versions/3.11.7/bin/platforms" ...
Cannot load library /home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so: (libxcb-icccm.so.4: cannot open shared object file: No such file or directory)
QLibraryPrivate::loadPlugin failed on "/home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so" : "Cannot load library /home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so: (libxcb-icccm.so.4: 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)
2.2 Use ldd to check the dependent libraries for libqxcb.so in the line that says Cannot load library in the output of step 2.1. In other words, execute the following command
```bash
# If your libqxcb.so path is /home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so
$ ldd /home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so
# you will get the following output
~$ ldd /home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/libqxcb.so
linux-vdso.so.1 (0x00007fffc7fd7000)
libQt5XcbQpa.so.5 => /home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/../../lib/libQt5XcbQpa.so.5 (0x00007f2df7200000)
libfontconfig.so.1 => /lib/x86_64-linux-gnu/libfontconfig.so.1 (0x00007f2df7952000)
libfreetype.so.6 => /lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007f2df788a000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f2df786e000)
libQt5Gui.so.5 => /home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/../../lib/libQt5Gui.so.5 (0x00007f2df6800000)
libQt5DBus.so.5 => /home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/../../lib/libQt5DBus.so.5 (0x00007f2df6400000)
libQt5Core.so.5 => /home/noda/.pyenv/versions/3.11.7/lib/python3.11/site-packages/PyQt5/Qt5/plugins/platforms/../../lib/libQt5Core.so.5 (0x00007f2df5c00000)
libGL.so.1 => /lib/x86_64-linux-gnu/libGL.so.1 (0x00007f2df7579000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f2df7867000)
libX11-xcb.so.1 => /lib/x86_64-linux-gnu/libX11-xcb.so.1 (0x00007f2df7862000)
libxcb-icccm.so.4 => not found
libxcb-image.so.0 => not found
...
```
2.3 If the output of 2.2 says => not found, it means a dependent library is missing, so you should install it by finding out how to install the dependent library using the package manager you are using.
Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.
Aborted (core dumped)