qt.qpa.plugin: could not find the Qt platform plugin "xcb" in ""

IknowQT

If you run it after depoly from qtcreator to Raspberry Pi, this message appears and the program does not run.

apt install libxcb-xinerama0 is already installed.

I did a lot of searches related to this.

Build options:
  Mode ................................... release
  Optimize release build for size ........ no
  Building shared libraries .............. yes
  Using C standard ....................... C11
  Using C++ standard ..................... C++17
  Using ccache ........................... no
  Using new DTAGS ........................ no
  Relocatable ............................ yes
  Using precompiled headers .............. yes
  Using LTCG ............................. no
  Target compiler supports:
    NEON ................................. yes
  Build parts ............................ libs
Qt modules and options:
  Qt Concurrent .......................... yes
  Qt D-Bus ............................... yes
  Qt D-Bus directly linked to libdbus .... yes
  Qt Gui ................................. yes
  Qt Network ............................. yes
  Qt Sql ................................. yes
  Qt Testlib ............................. yes
  Qt Widgets ............................. yes
  Qt Xml ................................. yes
Support enabled for:
  Using pkg-config ....................... yes
  udev ................................... yes
  Using system zlib ...................... yes
  Zstandard support ...................... no
Qt Core:
  DoubleConversion ....................... yes
    Using system DoubleConversion ........ yes
  GLib ................................... yes
  iconv .................................. no
  ICU .................................... yes
  Built-in copy of the MIME database ..... yes
  Tracing backend ........................ <none>
  Logging backends:
    journald ............................. no
    syslog ............................... no
    slog2 ................................ no
  PCRE2 .................................. yes
    Using system PCRE2 ................... yes
Qt Network:
  getifaddrs() ........................... yes
  IPv6 ifname ............................ yes
  libproxy ............................... no
  Linux AF_NETLINK ....................... yes
  OpenSSL ................................ yes
    Qt directly linked to OpenSSL ........ no
  OpenSSL 1.1 ............................ yes
  DTLS ................................... yes
  OCSP-stapling .......................... yes
  SCTP ................................... no
  Use system proxies ..................... yes
  GSSAPI ................................. no
Qt Gui:
  Accessibility .......................... yes
  FreeType ............................... yes
    Using system FreeType ................ yes
  HarfBuzz ............................... yes
    Using system HarfBuzz ................ yes
  Fontconfig ............................. yes
  Image formats:
    GIF .................................. yes
    ICO .................................. yes
    JPEG ................................. yes
      Using system libjpeg ............... yes
    PNG .................................. yes
      Using system libpng ................ yes
  Text formats:
    HtmlParser ........................... yes
    CssParser ............................ yes
    OdfWriter ............................ yes
    MarkdownReader ....................... yes
      Using system libmd4c ............... no
    MarkdownWriter ....................... yes
  EGL .................................... yes
  OpenVG ................................. no
  OpenGL:
    Desktop OpenGL ....................... no
    OpenGL ES 2.0 ........................ yes
    OpenGL ES 3.0 ........................ yes
    OpenGL ES 3.1 ........................ yes
    OpenGL ES 3.2 ........................ yes
  Vulkan ................................. yes
  Session Management ..................... yes
Features used by QPA backends:
  evdev .................................. yes
  libinput ............................... yes
  INTEGRITY HID .......................... no
  mtdev .................................. yes
  tslib .................................. no
  xkbcommon .............................. yes
  X11 specific:
    XLib ................................. yes
    XCB Xlib ............................. yes
    EGL on X11 ........................... yes
    xkbcommon-x11 ........................ yes
QPA backends:
  DirectFB ............................... no
  EGLFS .................................. yes
  EGLFS details:
    EGLFS OpenWFD ........................ no
    EGLFS i.Mx6 .......................... no
    EGLFS i.Mx6 Wayland .................. no
    EGLFS RCAR ........................... no
    EGLFS EGLDevice ...................... yes
    EGLFS GBM ............................ yes
    EGLFS VSP2 ........................... no
    EGLFS Mali ........................... no
    EGLFS Raspberry Pi ................... no
    EGLFS X11 ............................ yes
  LinuxFB ................................ yes
  VNC .................................... yes
Qt Sql:
  SQL item models ........................ yes
Qt Widgets:
  GTK+ ................................... no
  Styles ................................. Fusion Windows
Qt PrintSupport:
  CUPS ................................... yes
Qt Sql Drivers:
  DB2 (IBM) .............................. no
  InterBase .............................. no
  MySql .................................. no
  OCI (Oracle) ........................... no
  ODBC ................................... yes
  PostgreSQL ............................. yes
  SQLite2 ................................ no
  SQLite ................................. yes
    Using system provided SQLite ......... no
  TDS (Sybase) ........................... yes
Qt Testlib:
  Tester for item models ................. yes
Serial Port:
  ntddmodm ............................... no
Qt SerialBus:
  Socket CAN ............................. yes
  Socket CAN FD .......................... yes
  SerialPort Support ..................... yes
Further Image Formats:
  JasPer ................................. no
  MNG .................................... no
  TIFF ................................... yes
    Using system libtiff ................. yes
  WEBP ................................... yes
    Using system libwebp ................. yes
Qt QML:
  QML network support .................... yes
  QML debugging and profiling support .... yes
  QML just-in-time compiler .............. yes
  QML sequence object .................... yes
  QML XML http request ................... yes
  QML Locale ............................. yes
Qt QML Models:
  QML list model ......................... yes
  QML delegate model ..................... yes
Qt Quick:
  Direct3D 12 ............................ no
  AnimatedImage item ..................... yes
  Canvas item ............................ yes
  Support for Qt Quick Designer .......... yes
  Flipable item .......................... yes
  GridView item .......................... yes
  ListView item .......................... yes
  TableView item ......................... yes
  Path support ........................... yes
  PathView item .......................... yes
  Positioner items ....................... yes
  Repeater item .......................... yes
  ShaderEffect item ...................... yes
  Sprite item ............................ yes
QtQuick3D:
  Assimp ................................. yes
  System Assimp .......................... no
Qt Scxml:
  ECMAScript data model for QtScxml ...... yes
Qt Gamepad:
  SDL2 ................................... no
Qt 3D:
  Assimp ................................. yes
  System Assimp .......................... no
  Output Qt3D GL traces .................. no
  Use SSE2 instructions .................. no
  Use AVX2 instructions .................. no
  Aspects:
    Render aspect ........................ yes
    Input aspect ......................... yes
    Logic aspect ......................... yes
    Animation aspect ..................... yes
    Extras aspect ........................ yes
Qt 3D Renderers:
  OpenGL Renderer ........................ yes
  RHI Renderer ........................... no
Qt 3D GeometryLoaders:
  Autodesk FBX ........................... no
Qt Bluetooth:
  BlueZ .................................. yes
  BlueZ Low Energy ....................... yes
  Linux Crypto API ....................... yes
  Native Win32 Bluetooth ................. no
  WinRT Bluetooth API (desktop & UWP) .... no
  WinRT advanced bluetooth low energy API (desktop & UWP) . no
Qt Sensors:
  sensorfw ............................... no
Qt Quick Controls 2:
  Styles ................................. Default Fusion Imagine Material Universal
Qt Quick Templates 2:
  Hover support .......................... yes
  Multi-touch support .................... yes
Qt Positioning:
  Gypsy GPS Daemon ....................... no
  WinRT Geolocation API .................. no
Qt Location:
  Qt.labs.location experimental QML plugin . yes
  Geoservice plugins:
    OpenStreetMap ........................ yes
    HERE ................................. yes
    Esri ................................. yes
    Mapbox ............................... yes
    MapboxGL ............................. yes
    Itemsoverlay ......................... yes
QtXmlPatterns:
  XML schema support ..................... yes
Qt Multimedia:
  ALSA ................................... yes
  GStreamer 1.0 .......................... yes
  GStreamer 0.10 ......................... no
  Video for Linux ........................ yes
  OpenAL ................................. yes
  PulseAudio ............................. yes
  Resource Policy (libresourceqt5) ....... no
  Windows Audio Services ................. no
  DirectShow ............................. no
  Windows Media Foundation ............... no
Qt TextToSpeech:
  Flite .................................. no
  Flite with ALSA ........................ no
  Speech Dispatcher ...................... no
Qt Tools:
  Qt Assistant ........................... yes
  Qt Designer ............................ yes
  Qt Distance Field Generator ............ yes
  kmap2qmap .............................. yes
  Qt Linguist ............................ yes
  Mac Deployment Tool .................... no
  makeqpf ................................ yes
  pixeltool .............................. yes
  qdbus .................................. yes
  qev .................................... yes
  Qt Attributions Scanner ................ yes
  qtdiag ................................. yes
  qtpaths ................................ yes
  qtplugininfo ........................... yes
  Windows deployment tool ................ no
  WinRT Runner Tool ...................... no
Qt Tools:
  QDoc ................................... yes

Note: Also available for Linux: linux-clang linux-icc

I'll post a build summary. Were there any issues with the build?

export QT_DEBUG_PLUGINS=1

If you run it after using the debug option, there will be no debug related messages.

When I move the mouse, a failed to move cursor on screen HDMI1:-13 message occurs and every second Could not queue DRM page flip on screen HDMI1 (Permission deneied) message is displayed.

IknowQT

@IknowQT

./analogclock -platform xcb
QFactoryLoader::QFactoryLoader() checking directory path "/usr/local/qt5.15/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/local/qt5.15/plugins/platforms/libqeglfs.so"
Found metadata in lib /usr/local/qt5.15/plugins/platforms/libqeglfs.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "eglfs"
        ]
    },
    "archreq": 0,
    "className": "QEglFSIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("eglfs")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/qt5.15/plugins/platforms/libqlinuxfb.so"
Found metadata in lib /usr/local/qt5.15/plugins/platforms/libqlinuxfb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "linuxfb"
        ]
    },
    "archreq": 0,
    "className": "QLinuxFbIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("linuxfb")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/qt5.15/plugins/platforms/libqminimal.so"
Found metadata in lib /usr/local/qt5.15/plugins/platforms/libqminimal.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimal"
        ]
    },
    "archreq": 0,
    "className": "QMinimalIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("minimal")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/qt5.15/plugins/platforms/libqminimalegl.so"
Found metadata in lib /usr/local/qt5.15/plugins/platforms/libqminimalegl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimalegl"
        ]
    },
    "archreq": 0,
    "className": "QMinimalEglIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("minimalegl")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/qt5.15/plugins/platforms/libqoffscreen.so"
Found metadata in lib /usr/local/qt5.15/plugins/platforms/libqoffscreen.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "offscreen"
        ]
    },
    "archreq": 0,
    "className": "QOffscreenIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("offscreen")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/qt5.15/plugins/platforms/libqvnc.so"
Found metadata in lib /usr/local/qt5.15/plugins/platforms/libqvnc.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "vnc"
        ]
    },
    "archreq": 0,
    "className": "QVncIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("vnc")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/qt5.15/plugins/platforms/libqwebgl.so"
Found metadata in lib /usr/local/qt5.15/plugins/platforms/libqwebgl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "webgl"
        ]
    },
    "archreq": 0,
    "className": "QWebGLIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("webgl")
QFactoryLoader::QFactoryLoader() checking directory path "/home/pi/home/pi/platforms" ...
qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in ""
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, webgl.

./analogclock -platform xcb
When I run this command, I get this message:

JonB

@IknowQT
There are many possibilities if you Google for e.g.
qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in ""

So far as I can see you do not have any xcb plugin library installed at all. You should have a file /usr/local/qt5.15/plugins/platforms/libqxcb.so, but I do not think you even have that? In which case, how did you install what? I am not an expert, but if it is supposed to come from your XCB Xlib ............................. yes line I don't think it has been installed on your RPi?

IknowQT

@JonB

Should the libqxcb.so file be in the path you said? As you said I don't have that file.

Now that I know the cause, is there a way to fix it?

JonB

@IknowQT said in qt.qpa.plugin: could not find the Qt platform plugin "xcb" in "":

Should the libqxcb.so file be in the path you said? As you said I don't have that file.

I believe so. Look at the other paths in the diagnostic output.

Now that I know the cause, is there a way to fix it?

Somehow by installing that file, plus any dependencies. Not my area, someone else may know. But how/what did you do to install these library files on your RPi? Did you look through some of the Google hits to see if any apply to your case?

IknowQT

@JonB

I was looking. Most recommended apt install libxcb-xinerama, but I am already up to date and the result is the same

JonB

@IknowQT
I think that is the other way round: I believe libxcb-xinerama is a library needed for the xcb library, and you have not got that far. Don't you need something like

apt install libxcb
# or
apt install libqxcb

Press the Tab key (possibly twice) at the end of these lines and the shell should show you names of whatever packages match the prefixes.

IknowQT

@JonB
It says the package you said could not be found.

JonB

@IknowQT
Are you compiling and deploying all on RPi, or are you cross-compiling for RPi from another host?
What about trying

find / -name libqxcb.so -ls 2>/dev/null

on your RPi, and also on host platform if you are cross-compiling?

What about perhaps https://forum.qt.io/topic/125582/qt-5-15-2-do-not-build-libqxcb-so-but-at-the-same-time-qt-5-14-0-successfully-build-libqxcb-so :

Seems like I fix the problem:

sudo apt-get install libxcb-util-dev

It required for build Qt 5.15.x but not required for Qt 5.14.x

?

IknowQT

@JonB

I have built a cross-compilation environment in Ubuntu and am running it by uploading it to Raspberry Pi.

find / -name libqxcb.so -ls 2>/dev/null

Here is the result I tried.

devqt@devqt-desktop:/$ find / -name libqxcb.so -ls 2>/dev/null
 29906776     12 -rwxrwxrwx   1 root     root         9680  9월 28  2020 /root/rpi-qt_32/sysroot/usr/lib/arm-linux-gnueabihf/qt5/plugins/platforms/libqxcb.so
 29127237     12 -rwxrwxrwx   1 root     root         9680  9월 28  2020 /root/rpi-qt_32/sysroot/lib/arm-linux-gnueabihf/qt5/plugins/platforms/libqxcb.so

sudo apt-get install libxcb-util-dev
It says package not found.
instead

sudo apt-get install libxcb-util0-dev
sudo apt-get install libxcb-util0

There are two packages, so I installed both, but it says that they are already installed.

JonB

@IknowQT
These look possibly like the required files. Since I know nothing about RPi or cross-compiling for it, I do not know whether these are situated on the cross-compiling machine or on the RPI target. I would guess the compiling machine, but don't know.

If they are on the compiling machine don't they need copying to the RPi?
If they are on the RPi then where are they, aren't they supposed to be in /usr/local/qt5.15/plugins/platforms or somewhere Qt plugins are sought?

I know nothing about "after depoly from qtcreator to Raspberry Pi", check whatever instructions you are using?

Earlier:

sudo apt-get install libxcb-util0-dev
sudo apt-get install libxcb-util0

and you said "It says the package you said could not be found."

If these worked did you really follow my instruction:

apt install libxcb
# or
apt install libqxcb

Press the Tab key (possibly twice) at the end of these lines and the shell should show you names of whatever packages match the prefixes

or did you just ignore what I said about the Tab key?

IknowQT

/lib/arm-linux-gnueabihf/qt5/plugins/platforms/libqxcb.so

The Raspberry Pi also has this file.
it's too hard

JonB

@IknowQT said in qt.qpa.plugin: could not find the Qt platform plugin "xcb" in "":

it's too hard

Best of luck.

SiGa

I had the same or similar issue.
libqxcb was not present in (install_dir is the path provided with -prefix during configuration)

install_dir/plugins/platforms

I had to install the recommended packages from https://doc.qt.io/qt-6/linux-requirements.html and then rebuild qt from source(configure, compile, install, copy to target).
Additionally my copy command did not copy libqxcb, so I used compressed version for copying.
In the end I was missing some libs on the target, machine. After this, it worked.
May it be helpful for some future visitor.