qt.qpa.xcb: could not connect to display :0

SSJCarti · 27 Oct 2020, 18:52

Hi, I've been trying to set up QtSLiM and it isn't working.

I enter export LIBGL_ALWAYS_INDIRECT=; export DISPLAY=:0; ~/build/QtSLiM

and then this is the result

Any help would be greatly appreciated

SGaist · wrote on 27 Oct 2020, 16:57

Hi and welcome to devnet,

Start your application with the QT_DEBUG_PLUGINS environment variable set to 1. That will give you more information about what is going wrong.

If you have a recent version of Qt, I would guess you are missing libxinerama.

[edit: added missing words SGaist]

SSJCarti · 27 Oct 2020, 17:55

What command do I do to set the plugins to 1

when I tried what you put, this popped up

JonB · 28 Oct 2020, 13:14

@SSJCarti
It's an environment variable. export QT_DEBUG_PLUGINS=1.

SSJCarti · wrote on 27 Oct 2020, 18:32

When I did that, nothing happened

SGaist · wrote on 27 Oct 2020, 18:35

Now you have to start your application to see the debug output.

SSJCarti · 27 Oct 2020, 18:47

So now I should try this command again? export LIBGL_ALWAYS_INDIRECT=; export DISPLAY=:0; ~/build/QtSLiM

Also I can only post once every 600 seconds

I am also doing thin on a windows 10 computer using ubuntu

JonB · wrote on 27 Oct 2020, 18:47

@SSJCarti said in qt.qpa.xcb: could not connect to display :0:

So now I should try this command again? export LIBGL_ALWAYS_INDIRECT=; export DISPLAY=:0; ~/build/QtSLiM

Yes.

Pablo J. Rogina · wrote on 27 Oct 2020, 18:52

@SSJCarti said in qt.qpa.xcb: could not connect to display :0:

QtSLiM

It would be great you had provided a link to such application

and then this is the result

Please paste the output as text, not an screenshot so it's easier to copy/reply to such output

export DISPLAY=:0

If you export such variable, it's likely you want some X server to be available.
Which seems not the case by looking at your output could not connect to display :0

SSJCarti · 27 Oct 2020, 19:32

This is the link to the instructions for running the QtSlim, you have to go to section 2.4.5
http://benhaller.com/slim/SLiM_Manual.pdf
After running that this is what popped up

adduser@DESKTOP-991BCVH:~$ export LIBGL_ALWAYS_INDIRECT=; export DISPLAY=:0; ~/build/QtSLiM
QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqeglfs.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqeglfs.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"eglfs"
]
},
"archreq": 0,
"className": "QEglFSIntegrationPlugin",
"debug": false,
"version": 330752
}

Got keys from plugin meta data ("eglfs")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqlinuxfb.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqlinuxfb.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"linuxfb"
]
},
"archreq": 0,
"className": "QLinuxFbIntegrationPlugin",
"debug": false,
"version": 330752
}

Got keys from plugin meta data ("linuxfb")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqminimal.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqminimal.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"minimal"
]
},
"archreq": 0,
"className": "QMinimalIntegrationPlugin",
"debug": false,
"version": 330752
}

Got keys from plugin meta data ("minimal")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqminimalegl.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqminimalegl.so, metadata={
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"minimalegl"
]
},
"archreq": 0,
"className": "QMinimalEglIntegrationPlugin",
"debug": false,
"version": 330752
}

Got keys from plugin meta data ("minimalegl")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqoffscreen.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqoffscreen.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"offscreen"
]
},
"archreq": 0,
"className": "QOffscreenIntegrationPlugin",
"debug": false,
"version": 330752
}

Got keys from plugin meta data ("offscreen")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqvnc.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqvnc.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"vnc"
]
},
"archreq": 0,
"className": "QVncIntegrationPlugin",
"debug": false,
"version": 330752
}

Got keys from plugin meta data ("vnc")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so, metadata=
{
"IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
"MetaData": {
"Keys": [
"xcb"
]
},
"archreq": 0,
"className": "QXcbIntegrationPlugin",
"debug": false,
"version": 330752
}

Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/home/adduser/build/platforms" ...
loaded library "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so"
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

Pablo J. Rogina · wrote on 27 Oct 2020, 19:32

@SSJCarti said in qt.qpa.xcb: could not connect to display :0:

qt.qpa.xcb: could not connect to display :0

it seems you haven't looked at my previous post. You may need an X server running

SSJCarti · 27 Oct 2020, 21:43

I have a VcXsrv running. Also known as XLaunch

Pablo J. Rogina · wrote on 27 Oct 2020, 21:43

@SSJCarti said in qt.qpa.xcb: could not connect to display :0:

I have a VcXsrv running

According to this site:

VcXsrv makes it possible to run Linux GUI programs installed with WSL, the Windows Subsystem for Linux. In bash for Windows, setting the DISPLAY environment variable allows WSL programs to use the Windows GUI. For instance, if VcXsrv is configured to use display number zero, the command DISPLAY=:0 etr would run the game Extreme Tux Racer

Given that you're running VcXsrv, you may need to double check its configuration and what display it's exporting/providing to the Linux side of the Windows WSL (sorry but I don't have experience with Windows WSL to help more).

You may also want to check the videos here about VcXsrv & Win10 Linux Subsystems

SSJCarti · wrote on 27 Oct 2020, 22:03

thank you. Is there anyone else with potential ideas?

SSJCarti · 28 Oct 2020, 13:43

@JonB Do you have any ideas?

JonB · 28 Oct 2020, 14:18

@SSJCarti

loaded library "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so"
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.

I know little about, less than you or @Pablo-J-Rogina . But it does seem to me that whatever he is trying to ask/tell you about an X server --- either not running or somehow not found? --- is what is causing the problem here, given that it has said

loaded library "/usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so"
Could not load the Qt platform plugin "xcb" in "" even though it was found.

?

There are many Google hits for Could not load the Qt platform plugin "xcb", and we usually find that is an absent library like libxcb-xinerama.so.0. But here I am thinking you should Google for could not load the qt platform plugin "xcb" in "" even though it was found. The "even though it was found" being key. There are a bunch of hits on that, things like XDG_RUNTIME_DIR not giving you a good X environment. If I understood any of this :) that is what I would look through.

SSJCarti · 28 Oct 2020, 14:21

@JonB alright thank you ill look for that

JonB · 28 Oct 2020, 14:31

@SSJCarti
One thing: It seems to me there is a related discussion going on in https://forum.qt.io/topic/120349/run-qt-gui-application-inside-docker. I assume that Poster is not yourself too. At least, that seems to get the same message as you do:

loaded library "/home/user/app/platforms/libqxcb.so"
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.

So maybe worth a look?

EDIT @Pablo-J-Rogina has said below this would not be helpful to you, so don't! :)

Pablo J. Rogina · 28 Oct 2020, 15:41

@JonB said in qt.qpa.xcb: could not connect to display :0:

So maybe worth a look?

I don't think the goals/environments are the same... I'd say it will mislead OP here

SSJCarti · 28 Oct 2020, 17:04

@Pablo-J-Rogina so is my Xlaunch a xserver?