qt.qpa.xcb: could not connect to display error

deleted286 · wrote on 2 Apr 2021, 10:53

When i trying to run my project it gives me these errors

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.
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.

mrjj · 6 Apr 2021, 14:16

Hi
You mean run your project stand alone ?

Did you make a deployment folder for it ?

Colins2 · 3 Apr 2021, 13:41

Did you actually get QtCreator running?
I've just upgraded to 6.03 and the latest QtCreator andf now it won't even start up.
I get the same error message as you posted when I try to start it from Terminal.

I have uninstalled / reinstalled but it doesn't help.
This is on Debian, I haven't tried the upgrading the Windows installation yet.

JonB · 3 Apr 2021, 14:54

@Colins2
From a terminal export QT_DEBUG_PLUGINS=1. Then type the full path to the Creator executable.

Colins2 · 3 Apr 2021, 16:06

@JonB Thanks.
I tried that command and it worked partially.
It found all the other plugins and it also found libqxcb.so, in the same folder, but couldn't load it.
The spurious error message was:

QFactoryLoader::QFactoryLoader() looking at "/home/colins2/Qt/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so"
Found metadata in lib /home/colins2/Qt/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"xcb"
]
},
"archreq": 0,
"className": "QXcbIntegrationPlugin",
"debug": false,
"version": 331520
}

Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/home/colins2/Qt/Tools/QtCreator/bin/platforms" ...
Cannot load library /home/colins2/Qt/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so: (libxcb-util.so.1: cannot open shared object file: No such file or directory)
QLibraryPrivate::loadPlugin failed on "/home/colins2/Qt/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so" : "Cannot load library /home/colins2/Qt/Tools/QtCreator/lib/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, xcb.

Aborted

I say spurious because it found the file and read it and then said it didn't exist, followed by "couldn't load.....even though it was found"
Very puzzling

JonB · wrote on 3 Apr 2021, 16:06

@Colins2
Run ldd /home/colins2/Qt/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so. I think it's telling you it can't find a libxcb-util.so.1 required dependency, or another dependency of that.

Colins2 · 5 Apr 2021, 05:54

@JonB
Yes, that was it. ldd showed that I had libxcb-util.so.0 so I created a link in the same directory for libxcb-util.so.1 and now QtCreator is running.
Many thanks for your help

deleted286 · J JonB 3 Apr 2021, 13:41

@JonB said in qt.qpa.xcb: could not connect to display error:

@Colins2
From a terminal export QT_DEBUG_PLUGINS=1. Then type the full path to the Creator executable.

I did this step but im getting this error still

deleted286 · 5 Apr 2021, 05:56

@Colins2 how you created a link for it, libqxcb.so not found in my project

deleted286 · wrote on 5 Apr 2021, 05:56

This post is deleted!

Colins2 · 4 May 2021, 06:31

@suslucoder
Run the ldd command that JonB posted above and scroll through the list to try and find libxcb-util.so.?
You seem to have a similar problem to me in that Qt can't find the shared library.
ldd will show you where the libxcb file is. Qt wants version .so.1 and I had .so.0 and so it wouldn't run.
It's probably best to try and find the newer version from your distro repo, which I will do sometime but just to try it out I created a link called libxcb-util.so.1 linked back to ver so.0 so that Qt could find it.

deleted286 · 5 Apr 2021, 13:40

@Colins2 it doesnt find it. I will figure it out

ldd: /home/ilknur/Qt/Tools/QtCreator/lib/Qt/plugins/platforms/libqxcb.so: No such file or directory

Colins2 · 4 May 2021, 14:13

@suslucoder
libxcb-utils.so.* is not a Qt library so you may have to get it using your update tool.
Here's an excerpt from my system from the ldd command:
libxcb-icccm.so.4 => /lib/x86_64-linux-gnu/libxcb-icccm.so.4 (0x00007f11afec6000)
libxcb-image.so.0 => /lib/x86_64-linux-gnu/libxcb-image.so.0 (0x00007f11afcc1000)
libxcb-shm.so.0 => /lib/x86_64-linux-gnu/libxcb-shm.so.0 (0x00007f11afcba000)
libxcb-util.so.1 => /lib/x86_64-linux-gnu/libxcb-util.so.1 (0x00007f11afab3000)
libxcb-keysyms.so.1 => /lib/x86_64-linux-gnu/libxcb-keysyms.so.1 (0x00007f11af8b0000)
Obviously showing after the link I created.

deleted286 · 7 Apr 2021, 05:02

@mrjj sorry i didnt see this answer. Im trying to run on qt creator. ı didnt deploy my project.

mrjj · 7 Apr 2021, 11:18

@suslucoder

Ok. Is this by any chance ubuntu 20.04 ?

sometimes people have to install libxcb-xinerama.so

sometimes more.

sudo apt-get install libxcb-randr0-dev libxcb-xtest0-dev libxcb-xinerama0-dev libxcb-shape0-dev libxcb-xkb-dev
sudo apt-get install libxkbcommon-x11-dev

https://forum.qt.io/topic/93247/qt-qpa-plugin-could-not-load-the-qt-platform-plugin-xcb-in-even-though-it-was-found/64

but please check with ldd first, what is actually missing.

deleted286 · 7 Apr 2021, 11:25

@mrjj I've solve this problem with setting ld library path in environment variables.
But now, it says it cannot find another lib, i really stuck on it

jsulm · 4 Jul 2021, 11:27

@suslucoder said in qt.qpa.xcb: could not connect to display error:

i really stuck on it

You forgot to say which other lib is not found now...
Also, setting LD_LIBRARY_PATH is not necessary if all needed packages are installed properly.

Please take a look at https://doc.qt.io/qt-5/linux-requirements.html

deleted286 · 7 Apr 2021, 11:31

@jsulm when i run it on terminal
like

./my app name

there is no library that gives not found error

but when i tried to run it on qt creator it is give an error.
Other lib is that cannot found, libqmapcontrol.so.0
it is related with qmapcontrol

jsulm · 7 Apr 2021, 11:38

@suslucoder said in qt.qpa.xcb: could not connect to display error:

qmapcontrol

How did you install it (and where)?

deleted286 · 7 Apr 2021, 12:52

@jsulm i have a folder named as library in my project folder.
And i give a path for it my my .pro file.
I dont know how it is installed, i take the project from who worked here before me.
But it works perfect, till the day i tried to deploy.
But i deployed it to another folder, i didnt touch the orijinal project