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

hskoglund

Hi, the good news is that I can read the log, the bad news is that it shows successful launches of Qt Creator (so Qt Creator works fine) but nowhere is textLabel_Ex mentioned :-(

Yash_r

@hskoglund @jsulm @SGaist
textLabel_Ex is not the only program being affected like this. The error is present while deploying any app to the Beaglebone black.

Is there anything else that i can do to share some more information which can help you to understand the issue better?

Regards,
Yash

hskoglund

Hi, a log from an unsuccessful launch of any Qt app on the Beaglebone black.

Yash_r

@hskoglund
I have a cross-compile setup here, building the Qt apps on an ubuntu 20.04 LTS machine and deploying the built app to the Beaglebone Black (running Debian Bullseye distro) and checking the app working over a vnc connection.

Also, the app is not running in the qtcreator app, but is copied onto the BBB's /opt/ directory and the app can be executed manually from there.

@hskoglund said in qt.qpa.xcb: could not connect to display qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.:

a log from an unsuccessful launch of any Qt app on the Beaglebone black.

So, any particular process on how to get that particular log?

Yash_r

@hskoglund @jsulm @SGaist
Checking to see if anyone can further assist me with this issue as I am not able to debug the code from the Qt creator because of this very issue.

I would be able to provide any more information needed to better understand the issue.

SGaist

How many Qt versions do you have on your device ?

Yash_r

@SGaist
As far as i can see in the Options -> Kits, i have only 5.12.1 version configured for Beaglebone black.
(

SGaist

I meant on the device itself.

Yash_r

@SGaist
I am using the latest Debian Bullseye distro which is pretty much the latest available (updated from Debian Buster as a clean install).

So, the device is new and only has the Qt5,12,1,

SGaist

And it's the one you cross-compiled ?

Yash_r

@SGaist
Yes, Qt5.12.1 is the only version i have installed on my PC and using it for cross-compilation to the BBB.

Is there something that I am missing or might've messed up?

SGaist

When starting directly on the BBB, do you use the same backend ?

Yash_r

@SGaist said in qt.qpa.xcb: could not connect to display qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.:

do you use the same backend ?

Same backend?? Can you tell me what backend is being asked about?

@SGaist said in qt.qpa.xcb: could not connect to display qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.:

When starting directly on the BBB

Also I cannot directly start Qtcreator on BBB, since i don't have it installed on the BBB, and only use the cross-compilation on the ubuntu system to compile and deploy the app to the BBB (and nothing else)....don't know if that makes sense.

SGaist

Backed: xcb, eglfs, etc.

No need for Qt Creator on your target, I meant literally starting your application on it, for example through the command line.

Yash_r

@SGaist
When i run, any app on the target, from the terminal, I see the following output on the terminal:

SGaist

So it looks like your X server installation is incomplete to run Qt applications with the xcb backend. I would start by fixing that.

Yash_r

@SGaist

Can you help me with how to fix the incomplete X server installation? Or help provide some resource which can be helpful?

jsulm

@Yash_r Install libxcb-xkb1 package on your target device

Yash_r

@jsulm
That package is already installed according to the apt-install as can be seen in the below image:

Also, when i try to run the app (as debian user) from the terminal, i get the following error:

jsulm

@Yash_r Why do you start it with sudo?! By default starting GUI apps with sudo is not allowed for security reasons.