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

hskoglund

Indeed, the apt version of Qt you've got is 5.9.5. which does not play well with 5.12.9 :-(

Easiest short-term solution to get AppImage working is to try downgrade your 5.12.9 to 5.9.5 (with a bit of luck any 5.9.x version will do, but see if you can find 5.9.5 first).

(Long-term: try purging all apt-flavored Qt stuff from your Ubuntu system and rely solely on Qt's online installer.)

singhravi

@hskoglund Thanks for the confirmation!
Actually as per the application doc, its required to be 5.12 or greater,
For Desktop : you will need Qt5 (5.12 or newer). C++11 support is required!

I've uninstalled qt5-doc and other dependent packages installed via apt and built it again but xcb error is still there.
I'm checking if there is anything else remained to be removed.
Will update.

hskoglund

@singhravi To get rid of that faulty libQt5XcbQpa.so.5, try:

sudo apt remove libqt5gui5

(note: just guessing..)

singhravi

@hskoglund Yeah this should remove it. But wouldn't this library be needed by the Qt installed by online installer?
Let me run the build after removing this meanwhile.

singhravi

@hskoglund Actually other programs are depending on this qt library installed. Like VLC player, screen recorder and other Qt based apps.
So doing sudo apt remove libqt5gui5 would also remove those apps.

hskoglund

If those other programs are installed using apt, then apt should warn you if you issue a sudo apt remove libqt5gui5, then other programs are dependent on it (I think so). But I suggest yoy go for it and try the AppImage. Later, if the VLC player malfunctions, you can always do:
sudo apt install libqt5gui5

Also, about the Qt version installed by the online installer: it resides 100% in your $HOME directory, it does not touch anything in /usr/lib/x86_64-linux-gnu, nor does it need any Qt files to be installed in /usr/lib/x86_64-linux-gnu.

Only disadvantage is that, since apt is unaware of it, you have to keep it updated yourself (but Qt Creator has a nice plugin that periodically checks that for you).

singhravi

@hskoglund Yup, when ahead with this as the primary focus right now is to get this going.
And then i ran the command to create the build as well.
But it failed as qmake was not able to find Qt.

[qt/stdout] Found Qt modules: concurrent core dbus gui network qml quick quickcontrols2 quicktemplates2 svg texttospeech widgets 
[qt/stdout] Extra Qt modules:  
[qt/stdout] Using qmake: /usr/bin/qmake 
[qt/stdout] ERROR: Call to qmake failed: qmake: could not find a Qt installation of ''
[qt/stdout]  
[qt/stdout] ERROR: Failed to query Qt paths using qmake -query

Should i set some environment variable or create some softlinks for installed Qt to be used?
Something of that sort should fixed this i think.

hskoglund

Hmm, if that /usr/bin/qmake is still around, you should get rid of it (I think it's qtchooser):

sudo apt remove qtchooser

Then to point the linphone-desktop package to where your 5.12.9 is, on their github page it says, set these exports:
Qt5_DIR="~/Qt/5.12.9/gcc_64/lib/cmake"
PATH="~/Qt/5.12.9/gcc_64/bin/:$PATH"

singhravi

@hskoglund
The env variables, Qt5_DIR and PATH are set with what you suggested.
I think qmake is required that is why i must have installed it.
I've ran the build again. Lets see.

hskoglund

BTW, found another option: if you can upgrade your Ubuntu 18.04 to 20.04 then you're in luck: the Qt version installed by apt on Ubuntu 20.04 is 5.12.8 :-)

hskoglund

@singhravi Your Qt 5.12.9 has the qmake program in ~/Qt/5.12.9/gcc_64/bin/ so that PATH export setting should point the script to the correct qmake.

singhravi

@hskoglund I believe we've found the solution to this.
The problem was ~ (tlide) was not working with .zshrc config.
Hence qmake and other binary were not being found.
I've changed it to the absolute path now.
Running the build again. Lets see :)

singhravi

It Worked! :facepalm: :D
Thanks a lot @hskoglund for helping me troubleshoot this! You're great.
So the problem was a ~ from the beginning. This was too silly.
Build is sucsessful and Package is running fine now.

hskoglund

Hah, so it was a ~ that sent you on a wild goose chase!
(tildes can be a PITA, I remember tripping on them when trying to ssh into Ubuntu from Windows)
Anways, glad to hear its working now :-)

Jalpesh

@hskoglund thank Man!

sudo apt remove qtchooser
sudo apt install libqt5gui5

boom.... its work

chEguy

Guys I still am getting this error

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: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, xcb.
Aborted

BTW I am using Ubuntu20 on Windows10 with xcvsrv as X server

chEguy

I actually am not able to connect it to the display

Please help

hskoglund

Hi just guessing but maybe the solution in this post will help you too.

Matriarch

@Lengendary This is working solution for me, thank you

sudo apt-get install libxcb-xinerama0

aurelien

I know it is considered as a good software to build good software, but the point is here:

When you follow an installation guide step by step and make everything correctly, and the stuff does not works, that just mean it have been made with foot (from the stuff to the documentation.)

Really for thus who do their best, but it just not works on Debian 10 without doing weird things that should not be done out of the installation documentation.

Good luck