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

[SGaist]

Hi and welcome to devnet,

Start Qt Creator with the QT_DEBUG_PLUGINS environment variable set to 1 to see exactly what fails.

[hmserenade]

@SGaist
Hi there.
I turned on QT_DEBUG_PLUGINS:

[me@localhost ~]$ export QT_DEBUG_PLUGINS=1

And got the following output:

[me@localhost ~]$ qtcreator
QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin/qtcreator_install/lib/Qt/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/qtcreator_install/lib/Qt/plugins/platforms/libqlinuxfb.so"
Found metadata in lib /usr/bin/qtcreator_install/lib/Qt/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/bin/qtcreator_install/lib/Qt/plugins/platforms/libqminimal.so"
Found metadata in lib /usr/bin/qtcreator_install/lib/Qt/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/bin/qtcreator_install/lib/Qt/plugins/platforms/libqoffscreen.so"
Found metadata in lib /usr/bin/qtcreator_install/lib/Qt/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/bin/qtcreator_install/lib/Qt/plugins/platforms/libqvnc.so"
Found metadata in lib /usr/bin/qtcreator_install/lib/Qt/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/bin/qtcreator_install/lib/Qt/plugins/platforms/libqwayland-generic.so"
Found metadata in lib /usr/bin/qtcreator_install/lib/Qt/plugins/platforms/libqwayland-generic.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "wayland"
        ]
    },
    "archreq": 0,
    "className": "QWaylandIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("wayland")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/qtcreator_install/lib/Qt/plugins/platforms/libqwebgl.so"
Found metadata in lib /usr/bin/qtcreator_install/lib/Qt/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 "/usr/bin/qtcreator_install/bin/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: linuxfb, minimal, offscreen, vnc, wayland, webgl.

Aborted (core dumped)
[me@localhost ~]$ 

Yet I still don't get what's going on here. I'm currently doing all this on a CentOS 7 Virtualbox VM. Could you offer any insight? Thanks!

[jsulm]

@hmserenade said in qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in "":

But installing those packages didn't resolve the issue.

It is not enough to install these packages. You need to rebuild Qt so, that xcb plug-in is built. Check output of the configure command to see whether xcb was activated or not.

[hmserenade]

@jsulm Hi, thanks for replying. In addition to those packages I also installed xcb-util-wm-devel, then rebuilt Qt and Qt Creator repeating the same steps, but the issue persists, I still couldn't get Qt creator running.

The output of Qt's configuration is:

[me@localhost qt-everywhere-src-5.15.10]$ ./configure
+ cd qtbase
+ /home/me/qt-everywhere-src-5.15.10/qtbase/configure -top-level 
Creating qmake...
...............................................................................................Done.
Info: creating super cache file /home/me/qt-everywhere-src-5.15.10/.qmake.super
Info: creating cache file /home/me/qt-everywhere-src-5.15.10/.qmake.cache
Info: creating stash file /home/me/qt-everywhere-src-5.15.10/.qmake.stash

Selecting Qt Edition.

Type 'c' if you want to use the Commercial Edition.
Type 'o' if you want to use the Open Source Edition.

Which edition of Qt do you want to use? o

This is the Qt Open Source Edition.
 
You are licensed to use this software under the terms of
the GNU Lesser General Public License (LGPL) version 3
or the GNU General Public License (GPL) version 2.
 
Type 'L' to view the GNU Lesser General Public License version 3 (LGPLv3).
Type 'G' to view the GNU General Public License version 2 (GPLv2).
Type 'y' to accept this license offer.
Type 'n' to decline this license offer.
 
Do you accept the terms of either license? y


Running configuration tests...
Checking for machine tuple... yes
Checking for valid makespec... yes
Checking for target architecture... x86_64
Checking for SSE2 instructions... yes
Checking for AES new instructions... yes
Checking for alloca() in alloca.h... yes
Checking for SSE3 instructions... yes
Checking for SSSE3 instructions... yes
Checking for SSE4.1 instructions... yes
Checking for SSE4.2 instructions... yes
Checking for AVX instructions... yes
Checking for AVX2 instructions... yes
Checking for AVX512 F instructions... yes
Checking for AVX512 BW instructions... yes
Checking for AVX512 CD instructions... yes
Checking for AVX512 DQ instructions... yes
Checking for AVX512 ER instructions... yes
Checking for AVX512 IFMA instructions... yes
Checking for AVX512 PF instructions... yes
Checking for AVX512 VBMI instructions... yes
Checking for AVX512 VL instructions... yes
Checking for C++14 support... yes
Checking for C++17 support... yes
Checking for C99 support... yes
Checking for C11 support... yes
Checking for pkg-config... yes
Checking for D-Bus >= 1.2... no
Checking for dlopen()... yes
Checking for new dtags support... yes
Checking for F16C instructions... yes
Checking for D-Bus >= 1.2 (host)... yes
Checking for Support for Intel Control-flow Enforcement Technology... no
Checking for udev... no
Checking for POSIX fallocate()... yes
Checking for precompiled header support... yes
Checking for RDRAND instruction... yes
Checking for RDSEED instruction... yes
Checking for symbol visibility support... yes
Checking for -Bsymbolic-functions support... yes
Checking for SHA new instructions... yes
Checking for Signaling NaN for doubles... yes
Checking for STL compatibility... yes
Checking for zlib... no
Checking for Intrinsics without -mXXX argument... yes
Checking for Zstandard... no
Checking for clock_gettime()... yes
Checking for POSIX monotonic clock... yes
Checking for C++11 <future>... yes
Checking for eventfd... yes
Checking for futimens()... yes
Checking for getauxval()... yes
Checking for getentropy()... no
Checking for GLib... no
Checking for GNU libc... yes
Checking for POSIX iconv... yes
Checking for ICU... no
Checking for inotify... yes
Checking for SysV IPC... yes
Checking for linkat()... yes
Checking for PCRE2... no
Checking for ppoll()... yes
Checking for renameat2()... no
Checking for slog2... no
Checking for statx() in libc... no
Checking for 64 bit atomics... yes
Checking for DoubleConversion... no
Checking for O_CLOEXEC... yes
Checking for C++11 <random>... yes
Checking for working std::atomic for function pointers... yes
Checking for OpenSSL Headers... no
Checking for getifaddrs()... yes
Checking for KRB5 GSSAPI Support... no
Checking for IPv6 ifname... yes
Checking for Linux AF_NETLINK sockets... yes
Checking for XCB >= 1.11... yes
Checking for XCB ICCCM >= 0.3.9... yes
Checking for XCB SHM... yes
Checking for XCB Image >= 0.3.9... no
Checking for Desktop OpenGL... yes
Checking for KMS... yes
Checking for DRM Atomic API... yes
Checking for EGL... no
Checking for evdev... yes
Checking for FreeType... no
Checking for GBM... no
Checking for LinuxFB... yes
Checking for mtdev... no
Checking for OpenVG... no
Checking for default QPA platform... xcb
Checking for HarfBuzz... no
Checking for libjpeg... no
Checking for libmd4c... no
Checking for tslib... no
Checking for Vulkan... no
Checking for XLib... yes
Checking for XCB Xlib... yes
Checking for xkbcommon >= 0.5.0... no
Checking for CUPS... no
Checking for DB2 (IBM)... no
Checking for InterBase... no
Checking for MySQL... no
Checking for OCI (Oracle)... no
Checking for ODBC... no
Checking for PostgreSQL... no
Checking for SQLite (version 2)... no
Checking for TDS (Sybase)... no
Checking for ntddmodm... no
Checking for Socket CAN... yes
Checking for Socket CAN FD... yes
Checking for 64bit pointers... yes
Checking for python... /usr/bin/python
Checking for Direct3D 12... no
Checking for Assimp... no
Checking for SDL2... no
Checking for Assimp... no
Checking for Autodesk FBX... no
Checking for Wayland client library... yes
Checking for Wayland cursor library... yes
Checking for wayland-scanner... yes
Checking for XComposite... no
Checking for Wayland EGL library... yes
Checking for wayland-server... yes
Checking for BlueZ... no
Checking for sensorfw... no
Checking for Gypsy... no
Checking for WinRT Geolocation API... no
Checking for ALSA... no
Checking for GStreamer 1.0... no
Checking for GStreamer 0.10... no
Checking for Video for Linux... yes
Checking for OpenAL... no
Checking for PulseAudio >= 0.9.10... no
Checking for libresourceqt5... no
Checking for Flite... no
Checking for Speech Dispatcher... no
Checking for libclang... no
Checking for architecture supported... yes
Checking for bison... yes
Checking for submodule initialized... yes
Checking for build path without whitespace... yes
Checking for platform supported... 
Checking for gperf... no
Checking for flex... yes
Checking for host pkg-config... /usr/bin/pkg-config
Checking for jumbo build merge limit... 8
Checking for node.js... 
Checking for linker supports -z noexecstack... yes
Checking for python2... /usr/bin/python2
Checking for d-bus... no
Checking for fontconfig... no
Checking for glib-2.0 >= 2.32.0... no
Checking for glibc > 2.16... yes
Checking for khr... yes
Checking for lcms2... no
Checking for libdrm... yes
Checking for libevent... no
Checking for libvpx... no
Checking for libwebp, libwebpmux and libwebpdemux... no
Checking for compatible libxml2 and libxslt... no
Checking for minizip... no
Checking for system ninja... yes
Checking for nss >= 3.26... no
Checking for opus... no
Checking for re2... no
Checking for snappy... no
Checking for x11... yes
Checking for xcomposite... no
Checking for xcursor... no
Checking for xi... no
Checking for xkbfile... no
Checking for xproto (glproto)... yes
Checking for xtst... no
Done running configuration tests.

Configure summary:

Build type: linux-g++ (x86_64, CPU features: mmx sse sse2)
Compiler: gcc 9.3.1
Configuration: sse2 aesni sse3 ssse3 sse4_1 sse4_2 avx avx2 avx512f avx512bw avx512cd avx512dq avx512er avx512ifma avx512pf avx512vbmi avx512vl compile_examples enable_new_dtags f16c largefile precompile_header rdrnd rdseed shani x86SimdAlways shared shared rpath release c++11 c++14 c++17 c++1z concurrent dbus reduce_exports reduce_relocations stl
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 ........................ yes
  Relocatable ............................ yes
  Using precompiled headers .............. yes
  Using LTCG ............................. no
  Target compiler supports:
    SSE .................................. SSE2 SSE3 SSSE3 SSE4.1 SSE4.2
    AVX .................................. AVX AVX2
    AVX512 ............................... F ER CD PF DQ BW VL IFMA VBMI
    Other x86 ............................ AES F16C RDRAND SHA
    Intrinsics without -mXXX option ...... yes
  Build parts ............................ libs examples tools
Qt modules and options:
  Qt Concurrent .......................... yes
  Qt D-Bus ............................... yes
  Qt D-Bus directly linked to libdbus .... no
  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 ................................... no
  Using system zlib ...................... no
  Zstandard support ...................... no
Qt Core:
  DoubleConversion ....................... yes
    Using system DoubleConversion ........ no
  GLib ................................... no
  iconv .................................. yes
  ICU .................................... no
  Built-in copy of the MIME database ..... yes
  Tracing backend ........................ <none>
  Logging backends:
    journald ............................. no
    syslog ............................... no
    slog2 ................................ no
  PCRE2 .................................. yes
    Using system PCRE2 ................... no
Qt Network:
  getifaddrs() ........................... yes
  IPv6 ifname ............................ yes
  libproxy ............................... no
  Linux AF_NETLINK ....................... yes
  OpenSSL ................................ no
    Qt directly linked to OpenSSL ........ no
  OpenSSL 1.1 ............................ no
  DTLS ................................... no
  OCSP-stapling .......................... no
  SCTP ................................... no
  Use system proxies ..................... yes
  GSSAPI ................................. no
Qt Gui:
  Accessibility .......................... yes
  FreeType ............................... yes
    Using system FreeType ................ no
  HarfBuzz ............................... yes
    Using system HarfBuzz ................ no
  Fontconfig ............................. no
  Image formats:
    GIF .................................. yes
    ICO .................................. yes
    JPEG ................................. yes
      Using system libjpeg ............... no
    PNG .................................. yes
      Using system libpng ................ no
  Text formats:
    HtmlParser ........................... yes
    CssParser ............................ yes
    OdfWriter ............................ yes
    MarkdownReader ....................... yes
      Using system libmd4c ............... no
    MarkdownWriter ....................... yes
  EGL .................................... no
  OpenVG ................................. no
  OpenGL:
    Desktop OpenGL ....................... yes
    OpenGL ES 2.0 ........................ no
    OpenGL ES 3.0 ........................ no
    OpenGL ES 3.1 ........................ no
    OpenGL ES 3.2 ........................ no
  Vulkan ................................. no
  Session Management ..................... yes
Features used by QPA backends:
  evdev .................................. yes
  libinput ............................... no
  INTEGRITY HID .......................... no
  mtdev .................................. no
  tslib .................................. no
  xkbcommon .............................. no
  X11 specific:
    XLib ................................. yes
    XCB Xlib ............................. yes
    EGL on X11 ........................... no
    xkbcommon-x11 ........................ no
QPA backends:
  DirectFB ............................... no
  EGLFS .................................. no
  LinuxFB ................................ yes
  VNC .................................... yes
Qt Sql:
  SQL item models ........................ yes
Qt Widgets:
  GTK+ ................................... no
  Styles ................................. Fusion Windows
Qt PrintSupport:
  CUPS ................................... no
Qt Sql Drivers:
  DB2 (IBM) .............................. no
  InterBase .............................. no
  MySql .................................. no
  OCI (Oracle) ........................... no
  ODBC ................................... no
  PostgreSQL ............................. no
  SQLite2 ................................ no
  SQLite ................................. yes
    Using system provided SQLite ......... no
  TDS (Sybase) ........................... no
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 ................. no
  WEBP ................................... yes
    Using system libwebp ................. no
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 .................. yes
  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 Wayland Drivers:
  EGL .................................... no
  Raspberry Pi ........................... no
  XComposite EGL ......................... no
  XComposite GLX ......................... no
  DRM EGL ................................ no
  libhybris EGL .......................... no
  Linux dma-buf server buffer integration . no
  Vulkan-based server buffer integration . no
  Shm emulation server buffer integration . yes
Qt Wayland Client Shell Integrations:
  xdg-shell .............................. yes
  xdg-shell unstable v5 (deprecated) ..... yes
  xdg-shell unstable v6 .................. yes
  ivi-shell .............................. yes
  wl-shell (deprecated) .................. yes
Qt Wayland Client ........................ yes
Qt Wayland Compositor .................... yes
Qt Wayland Compositor Layer Plugins:
  VSP2 hardware layer integration ........ no
Qt Bluetooth:
  BlueZ .................................. no
  BlueZ Low Energy ....................... no
  Linux Crypto API ....................... no
  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 ................................... no
  GStreamer 1.0 .......................... no
  GStreamer 0.10 ......................... no
  Video for Linux ........................ yes
  OpenAL ................................. no
  PulseAudio ............................. no
  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 ................................... no
Qt WebEngine Build Tools:
  Use System Ninja ....................... yes
  Jumbo Build Merge Limit ................ 8
  Developer build ........................ no
  Sanitizer .............................. no
  QtWebEngine required system libraries:
    fontconfig ........................... no
    dbus ................................. no
    nss .................................. no
    khr .................................. yes
    glibc ................................ yes
  Optional system libraries used:
    re2 .................................. no
    icu .................................. no
    libwebp, libwebpmux and libwebpdemux . no
    opus ................................. no
    ffmpeg ............................... no
    libvpx ............................... no
    snappy ............................... no
    glib ................................. no
    zlib ................................. no
    minizip .............................. no
    libevent ............................. no
    libxml2 and libxslt .................. no
    lcms2 ................................ no
    png .................................. no
    JPEG ................................. no
    harfbuzz ............................. no
    freetype ............................. no

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

Note: The following modules are not being compiled in this configuration:
    webenginecore
    webengine
    webenginewidgets
    pdf
    pdfwidgets

WARNING: QDoc will not be compiled, probably because libclang could not be located. This means that you cannot build the Qt documentation.

Either ensure that llvm-config is in your PATH environment variable, or set LLVM_INSTALL_DIR to the location of your llvm installation.
On Linux systems, you may be able to install libclang by installing the libclang-dev or libclang-devel package, depending on your distribution.
On macOS, you can use Homebrew's llvm package.
On Windows, you must set LLVM_INSTALL_DIR to the installation path.

WARNING: Tool gperf is required to build QtWebEngine.

WARNING: Tool gperf is required to build QtPdf.

WARNING: QtWebEngine will not be built.

WARNING: QtPdf will not be built.

Qt is now configured for building. Just run 'gmake'.
Once everything is built, you must run 'gmake install'.
Qt will be installed into '/usr/local/Qt-5.15.10'.

Prior to reconfiguration, make sure you remove any leftovers from
the previous build.

Looks like xcb is fine. Do you have any ideas? Thanks again!

[SGaist]

@hmserenade hi,

Are you getting the same debug output with regard to the plugins at startup ?

[hmserenade]

@SGaist Hi, thank you for replying, this is the debug output:

[me@localhost qt-creator-opensource-src-7.0.2]$ ./bin/qtcreator
QFactoryLoader::QFactoryLoader() checking directory path "/usr/local/Qt-5.15.10/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/local/Qt-5.15.10/plugins/platforms/libqlinuxfb.so"
Found metadata in lib /usr/local/Qt-5.15.10/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/Qt-5.15.10/plugins/platforms/libqminimal.so"
Found metadata in lib /usr/local/Qt-5.15.10/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/Qt-5.15.10/plugins/platforms/libqoffscreen.so"
Found metadata in lib /usr/local/Qt-5.15.10/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/Qt-5.15.10/plugins/platforms/libqvnc.so"
Found metadata in lib /usr/local/Qt-5.15.10/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/Qt-5.15.10/plugins/platforms/libqwayland-generic.so"
Found metadata in lib /usr/local/Qt-5.15.10/plugins/platforms/libqwayland-generic.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "wayland"
        ]
    },
    "archreq": 0,
    "className": "QWaylandIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("wayland")
QFactoryLoader::QFactoryLoader() looking at "/usr/local/Qt-5.15.10/plugins/platforms/libqwebgl.so"
Found metadata in lib /usr/local/Qt-5.15.10/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/lbh/qt-creator-opensource-src-7.0.2/bin/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: linuxfb, minimal, offscreen, vnc, wayland, webgl.

Aborted (core dumped)

Looks the same to me. At this point I'm not sure the plugin packages is the cause here. Thoughts?

[SGaist]

From the looks of it, your custom built Qt does not have the xcb plugin. You are likely missing one or more of the dependencies required to build it.

[hmserenade]

@SGaist Hi, thanks for replying.

Based on the configuration output of ./configure prior to building Qt, all things related to xcb seem to be fine.

The debug output of Qt Creator's launching also shows that QFactoryLoader::QFactoryLoader() was able to get keys by looking at /usr/local/Qt-5.15.10/plugins/platforms/.

According to the debug output, my issue occurs when QFactoryLoader::QFactoryLoader() looks at /home/lbh/qt-creator-opensource-src-7.0.2/bin/platforms, which is where I built Qt Creator. Does this suggest that the problem is with Qt Creator itself?

[SGaist]

The thing is: /usr/local/Qt-5.15.10/plugins/platforms/ seems to be missing the xcb plugin hence my prior comment about it.

[hmserenade]

@SGaist Hi, thanks for you advice. This is what I found following your advice:

[lbh@localhost platforms]$ pwd
/usr/local/Qt-5.15.10/plugins/platforms
[lbh@localhost platforms]$ ls
libqlinuxfb.so  libqoffscreen.so  libqwayland-generic.so
libqminimal.so  libqvnc.so        libqwebgl.so
[lbh@localhost platforms]$

Judging by file names, this directory indeed does not include any xcb-related plugins. But how should I build it? Prior to building Qt, I already have these xcb-related packages installed (found via rpm -qa | grep xcb):

xcb-util-keysyms-0.4.0-1.el7.x86_64
xcb-util-wm-devel-0.4.1-5.el7.x86_64
libxcb-1.13-1.el7.x86_64
libxcb-devel-1.13-1.el7.x86_64
xcb-util-renderutil-0.3.9-3.el7.x86_64
xcb-util-0.4.0-2.el7.x86_64
xcb-util-wm-0.4.1-5.el7.x86_64
xcb-util-image-0.4.0-2.el7.x86_64
xcb-util-devel-0.4.0-2.el7.x86_64

Am I still missing any prerequisites?

[hmserenade]

Update:
I rebuilt Qt 5.15 with ./configure -qpa xcb, yet the resulting plugins in /usr/local/Qt-5.15.10/plugins/platforms remains the same (I'm guessing the missing plugin should be called libqxcb.so, right?), and unsurprisingly, Qt Creator reports the same error upon launching. If the problem is with libqxcb.so, how should I build it? Similar posts mention install libxcb-util-devbut that's for Debian/Ubuntu distros, which I guess should correspond to libxcb-devel and/or xcb-util-devel on CentOS 7, both of which I've already installed prior to compiling.

[hmserenade]

Update:

I found this thread that should be closely related to my issue. Following their suggestions, I installed libxkbcommon-devel and libxkbcommon-x11-devel. Now I have these xcb and xkb related packages:

$ rpm -qa | grep xkb
libxkbcommon-x11-devel-0.7.1-3.el7.x86_64
libxkbfile-1.0.9-3.el7.x86_64
libxkbcommon-x11-0.7.1-3.el7.x86_64
libxkbcommon-devel-0.7.1-3.el7.x86_64
xorg-x11-xkb-utils-7.7-14.el7.x86_64
libxkbcommon-0.7.1-3.el7.x86_64
$ rpm -qa | grep xcb
xcb-util-keysyms-0.4.0-1.el7.x86_64
xcb-util-wm-devel-0.4.1-5.el7.x86_64
libxcb-1.13-1.el7.x86_64
libxcb-devel-1.13-1.el7.x86_64
xcb-util-renderutil-0.3.9-3.el7.x86_64
xcb-util-0.4.0-2.el7.x86_64
xcb-util-wm-0.4.1-5.el7.x86_64
xcb-util-image-0.4.0-2.el7.x86_64
xcb-util-devel-0.4.0-2.el7.x86_64

And mesa-libGL-devel is installed too.
Next, I tried to build Qt 5.15.10 with ./configure -xcb -xcb-xlib -bundled-xcb-xinput, which failed saying:

ERROR: Feature 'xcb' was enabled, but the pre-condition 'features.thread && libs.xcb && tests.xcb_syslibs && features.xkbcommon-x11' failed. 

Check config.log for details.

But config.log doesn't contain text mentioning any of the pre-conditions.

Here's the full configuration output:

[lbh@localhost qt-everywhere-src-5.15.10-0]$ ./configure -xcb -xcb-xlib -bundled-xcb-xinput
+ cd qtbase
+ /home/lbh/qt-everywhere-src-5.15.10-0/qtbase/configure -top-level -xcb -xcb-xlib -bundled-xcb-xinput
Creating qmake...
...............................................................................................Done.

Selecting Qt Edition.

Type 'c' if you want to use the Commercial Edition.
Type 'o' if you want to use the Open Source Edition.

Which edition of Qt do you want to use? o

This is the Qt Open Source Edition.
 
You are licensed to use this software under the terms of
the GNU Lesser General Public License (LGPL) version 3
or the GNU General Public License (GPL) version 2.
 
Type 'L' to view the GNU Lesser General Public License version 3 (LGPLv3).
Type 'G' to view the GNU General Public License version 2 (GPLv2).
Type 'y' to accept this license offer.
Type 'n' to decline this license offer.
 
Do you accept the terms of either license? y


Running configuration tests...
Checking for machine tuple... yes
Checking for valid makespec... yes
Checking for target architecture... x86_64
Checking for SSE2 instructions... yes
Checking for AES new instructions... yes
Checking for alloca() in alloca.h... yes
Checking for SSE3 instructions... yes
Checking for SSSE3 instructions... yes
Checking for SSE4.1 instructions... yes
Checking for SSE4.2 instructions... yes
Checking for AVX instructions... yes
Checking for AVX2 instructions... yes
Checking for AVX512 F instructions... yes
Checking for AVX512 BW instructions... yes
Checking for AVX512 CD instructions... yes
Checking for AVX512 DQ instructions... yes
Checking for AVX512 ER instructions... yes
Checking for AVX512 IFMA instructions... yes
Checking for AVX512 PF instructions... yes
Checking for AVX512 VBMI instructions... yes
Checking for AVX512 VL instructions... yes
Checking for C++14 support... yes
Checking for C++17 support... yes
Checking for C99 support... yes
Checking for C11 support... yes
Checking for pkg-config... yes
Checking for D-Bus >= 1.2... no
Checking for dlopen()... yes
Checking for new dtags support... yes
Checking for F16C instructions... yes
Checking for D-Bus >= 1.2 (host)... yes
Checking for Support for Intel Control-flow Enforcement Technology... no
Checking for udev... no
Checking for POSIX fallocate()... yes
Checking for precompiled header support... yes
Checking for RDRAND instruction... yes
Checking for RDSEED instruction... yes
Checking for symbol visibility support... yes
Checking for -Bsymbolic-functions support... yes
Checking for SHA new instructions... yes
Checking for Signaling NaN for doubles... yes
Checking for STL compatibility... yes
Checking for zlib... no
Checking for Intrinsics without -mXXX argument... yes
Checking for Zstandard... no
Checking for clock_gettime()... yes
Checking for POSIX monotonic clock... yes
Checking for C++11 <future>... yes
Checking for eventfd... yes
Checking for futimens()... yes
Checking for getauxval()... yes
Checking for getentropy()... no
Checking for GLib... no
Checking for GNU libc... yes
Checking for POSIX iconv... yes
Checking for ICU... no
Checking for inotify... yes
Checking for SysV IPC... yes
Checking for linkat()... yes
Checking for PCRE2... no
Checking for ppoll()... yes
Checking for renameat2()... no
Checking for slog2... no
Checking for statx() in libc... no
Checking for 64 bit atomics... yes
Checking for DoubleConversion... no
Checking for O_CLOEXEC... yes
Checking for C++11 <random>... yes
Checking for working std::atomic for function pointers... yes
Checking for OpenSSL Headers... no
Checking for getifaddrs()... yes
Checking for KRB5 GSSAPI Support... no
Checking for IPv6 ifname... yes
Checking for Linux AF_NETLINK sockets... yes
Checking for XCB >= 1.11... yes
Checking for XCB ICCCM >= 0.3.9... yes
Checking for XCB SHM... yes
Checking for XCB Image >= 0.3.9... no
Checking for Desktop OpenGL... yes
Checking for KMS... yes
Checking for DRM Atomic API... yes
Checking for EGL... no
Checking for evdev... yes
Checking for FreeType... no
Checking for GBM... no
Checking for LinuxFB... yes
Checking for mtdev... no
Checking for OpenVG... no
Checking for default QPA platform... xcb
Checking for HarfBuzz... no
Checking for libjpeg... no
Checking for libmd4c... no
Checking for tslib... no
Checking for Vulkan... no
Checking for XLib... yes
Checking for XCB Xlib... yes
Checking for xkbcommon >= 0.5.0... yes
Checking for xkbcommon-x11... yes
Checking for CUPS... no
Checking for DB2 (IBM)... no
Checking for InterBase... no
Checking for MySQL... no
Checking for OCI (Oracle)... no
Checking for ODBC... no
Checking for PostgreSQL... no
Checking for SQLite (version 2)... no
Checking for TDS (Sybase)... no
Checking for ntddmodm... no
Checking for Socket CAN... yes
Checking for Socket CAN FD... yes
Checking for 64bit pointers... yes
Checking for python... /usr/bin/python
Checking for Direct3D 12... no
Checking for Assimp... no
Checking for SDL2... no
Checking for Assimp... no
Checking for Autodesk FBX... no
Checking for Wayland client library... yes
Checking for Wayland cursor library... yes
Checking for wayland-scanner... yes
Checking for XComposite... no
Checking for Wayland EGL library... yes
Checking for wayland-server... yes
Checking for BlueZ... no
Checking for sensorfw... no
Checking for Gypsy... no
Checking for WinRT Geolocation API... no
Checking for ALSA... no
Checking for GStreamer 1.0... no
Checking for GStreamer 0.10... no
Checking for Video for Linux... yes
Checking for OpenAL... no
Checking for PulseAudio >= 0.9.10... no
Checking for libresourceqt5... no
Checking for Flite... no
Checking for Speech Dispatcher... no
Checking for libclang... no
Checking for architecture supported... yes
Checking for bison... yes
Checking for submodule initialized... yes
Checking for build path without whitespace... yes
Checking for platform supported... 
Checking for gperf... no
Checking for flex... yes
Checking for host pkg-config... /usr/bin/pkg-config
Checking for jumbo build merge limit... 8
Checking for node.js... 
Checking for linker supports -z noexecstack... yes
Checking for python2... /usr/bin/python2
Checking for d-bus... no
Checking for fontconfig... no
Checking for glib-2.0 >= 2.32.0... no
Checking for glibc > 2.16... yes
Checking for khr... yes
Checking for lcms2... no
Checking for libdrm... yes
Checking for libevent... no
Checking for libvpx... no
Checking for libwebp, libwebpmux and libwebpdemux... no
Checking for compatible libxml2 and libxslt... no
Checking for minizip... no
Checking for system ninja... yes
Checking for nss >= 3.26... no
Checking for opus... no
Checking for re2... no
Checking for snappy... no
Checking for x11... yes
Checking for xcomposite... no
Checking for xcursor... no
Checking for xi... no
Checking for xkbfile... no
Checking for xproto (glproto)... yes
Checking for xtst... no
Done running configuration tests.

Configure summary:

Build type: linux-g++ (x86_64, CPU features: mmx sse sse2)
Compiler: gcc 9.3.1
Configuration: sse2 aesni sse3 ssse3 sse4_1 sse4_2 avx avx2 avx512f avx512bw avx512cd avx512dq avx512er avx512ifma avx512pf avx512vbmi avx512vl compile_examples enable_new_dtags f16c largefile precompile_header rdrnd rdseed shani x86SimdAlways shared shared rpath release c++11 c++14 c++17 c++1z concurrent dbus reduce_exports reduce_relocations stl
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 ........................ yes
  Relocatable ............................ yes
  Using precompiled headers .............. yes
  Using LTCG ............................. no
  Target compiler supports:
    SSE .................................. SSE2 SSE3 SSSE3 SSE4.1 SSE4.2
    AVX .................................. AVX AVX2
    AVX512 ............................... F ER CD PF DQ BW VL IFMA VBMI
    Other x86 ............................ AES F16C RDRAND SHA
    Intrinsics without -mXXX option ...... yes
  Build parts ............................ libs examples tools
Qt modules and options:
  Qt Concurrent .......................... yes
  Qt D-Bus ............................... yes
  Qt D-Bus directly linked to libdbus .... no
  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 ................................... no
  Using system zlib ...................... no
  Zstandard support ...................... no
Qt Core:
  DoubleConversion ....................... yes
    Using system DoubleConversion ........ no
  GLib ................................... no
  iconv .................................. yes
  ICU .................................... no
  Built-in copy of the MIME database ..... yes
  Tracing backend ........................ <none>
  Logging backends:
    journald ............................. no
    syslog ............................... no
    slog2 ................................ no
  PCRE2 .................................. yes
    Using system PCRE2 ................... no
Qt Network:
  getifaddrs() ........................... yes
  IPv6 ifname ............................ yes
  libproxy ............................... no
  Linux AF_NETLINK ....................... yes
  OpenSSL ................................ no
    Qt directly linked to OpenSSL ........ no
  OpenSSL 1.1 ............................ no
  DTLS ................................... no
  OCSP-stapling .......................... no
  SCTP ................................... no
  Use system proxies ..................... yes
  GSSAPI ................................. no
Qt Gui:
  Accessibility .......................... yes
  FreeType ............................... yes
    Using system FreeType ................ no
  HarfBuzz ............................... yes
    Using system HarfBuzz ................ no
  Fontconfig ............................. no
  Image formats:
    GIF .................................. yes
    ICO .................................. yes
    JPEG ................................. yes
      Using system libjpeg ............... no
    PNG .................................. yes
      Using system libpng ................ no
  Text formats:
    HtmlParser ........................... yes
    CssParser ............................ yes
    OdfWriter ............................ yes
    MarkdownReader ....................... yes
      Using system libmd4c ............... no
    MarkdownWriter ....................... yes
  EGL .................................... no
  OpenVG ................................. no
  OpenGL:
    Desktop OpenGL ....................... yes
    OpenGL ES 2.0 ........................ no
    OpenGL ES 3.0 ........................ no
    OpenGL ES 3.1 ........................ no
    OpenGL ES 3.2 ........................ no
  Vulkan ................................. no
  Session Management ..................... yes
Features used by QPA backends:
  evdev .................................. yes
  libinput ............................... no
  INTEGRITY HID .......................... no
  mtdev .................................. no
  tslib .................................. no
  xkbcommon .............................. yes
  X11 specific:
    XLib ................................. yes
    XCB Xlib ............................. yes
    EGL on X11 ........................... no
    xkbcommon-x11 ........................ yes
QPA backends:
  DirectFB ............................... no
  EGLFS .................................. no
  LinuxFB ................................ yes
  VNC .................................... yes
Qt Sql:
  SQL item models ........................ yes
Qt Widgets:
  GTK+ ................................... no
  Styles ................................. Fusion Windows
Qt PrintSupport:
  CUPS ................................... no
Qt Sql Drivers:
  DB2 (IBM) .............................. no
  InterBase .............................. no
  MySql .................................. no
  OCI (Oracle) ........................... no
  ODBC ................................... no
  PostgreSQL ............................. no
  SQLite2 ................................ no
  SQLite ................................. yes
    Using system provided SQLite ......... no
  TDS (Sybase) ........................... no
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 ................. no
  WEBP ................................... yes
    Using system libwebp ................. no
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 .................. yes
  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 Wayland Drivers:
  EGL .................................... no
  Raspberry Pi ........................... no
  XComposite EGL ......................... no
  XComposite GLX ......................... no
  DRM EGL ................................ no
  libhybris EGL .......................... no
  Linux dma-buf server buffer integration . no
  Vulkan-based server buffer integration . no
  Shm emulation server buffer integration . yes
Qt Wayland Client Shell Integrations:
  xdg-shell .............................. yes
  xdg-shell unstable v5 (deprecated) ..... yes
  xdg-shell unstable v6 .................. yes
  ivi-shell .............................. yes
  wl-shell (deprecated) .................. yes
Qt Wayland Client ........................ yes
Qt Wayland Compositor .................... yes
Qt Wayland Compositor Layer Plugins:
  VSP2 hardware layer integration ........ no
Qt Bluetooth:
  BlueZ .................................. no
  BlueZ Low Energy ....................... no
  Linux Crypto API ....................... no
  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 ................................... no
  GStreamer 1.0 .......................... no
  GStreamer 0.10 ......................... no
  Video for Linux ........................ yes
  OpenAL ................................. no
  PulseAudio ............................. no
  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 ................................... no
Qt WebEngine Build Tools:
  Use System Ninja ....................... yes
  Jumbo Build Merge Limit ................ 8
  Developer build ........................ no
  Sanitizer .............................. no
  QtWebEngine required system libraries:
    fontconfig ........................... no
    dbus ................................. no
    nss .................................. no
    khr .................................. yes
    glibc ................................ yes
  Optional system libraries used:
    re2 .................................. no
    icu .................................. no
    libwebp, libwebpmux and libwebpdemux . no
    opus ................................. no
    ffmpeg ............................... no
    libvpx ............................... no
    snappy ............................... no
    glib ................................. no
    zlib ................................. no
    minizip .............................. no
    libevent ............................. no
    libxml2 and libxslt .................. no
    lcms2 ................................ no
    png .................................. no
    JPEG ................................. no
    harfbuzz ............................. no
    freetype ............................. no

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

Note: The following modules are not being compiled in this configuration:
    webenginecore
    webengine
    webenginewidgets
    pdf
    pdfwidgets

WARNING: Feature system-xcb-xinput is insignificant in this configuration, ignoring related command line option(s).

WARNING: QDoc will not be compiled, probably because libclang could not be located. This means that you cannot build the Qt documentation.

Either ensure that llvm-config is in your PATH environment variable, or set LLVM_INSTALL_DIR to the location of your llvm installation.
On Linux systems, you may be able to install libclang by installing the libclang-dev or libclang-devel package, depending on your distribution.
On macOS, you can use Homebrew's llvm package.
On Windows, you must set LLVM_INSTALL_DIR to the installation path.

WARNING: Tool gperf is required to build QtWebEngine.

WARNING: Tool gperf is required to build QtPdf.

WARNING: QtWebEngine will not be built.

WARNING: QtPdf will not be built.

ERROR: Feature 'xcb' was enabled, but the pre-condition 'features.thread && libs.xcb && tests.xcb_syslibs && features.xkbcommon-x11' failed.

Check config.log for details.

I'm now pretty sure my core issue is that libqxcb.so is not generated when building Qt. So far all attempts to build that plugin have failed. Any suggestions?

[hskoglund]

Hi, had a similar problem with Ubuntu 20.04, ended up installing these:
ibcrypto++8
libcrypto++-dev
libinput-dev
libssl-dev
libx11-doc
libx11-freedesktop-desktopentry-perl
libx11-guitest-perl
libx11-keyboard-perl
libx11-protocol-other-perl
libx11-windowhierarchy-perl
libx11-xcb-dev
libx11-xcb-perl
libxcb-composite0
libxcb-composite0-dev
libxcb-cursor0
libxcb-cursor-dev
libxcb-damage0
libxcb-damage0-dev
libxcb-doc
libxcb-dpms0
libxcb-dpms0-dev
libxcb-dri2-0-dev
libxcb-dri3-dev
libxcb-ewmh2
libxcb-ewmh-dev
libxcb-glx0-dev
libxcb-icccm4-dev
libxcb-image0-dev
libxcb-imdkit1
libxcb-imdkit-dev
libxcb-keysyms1-dev
libxcb-present-dev
libxcb-randr0-dev
libxcb-record0
libxcb-record0-dev
libxcb-render0-dev
libxcb-render-util0-dev
libxcb-res0-dev
libxcb-screensaver0
libxcb-screensaver0-dev
libxcb-shape0-dev
libxcb-shm0-dev
libxcb-sync-dev
libxcb-util0-dev
libxcb-util-dev
libxcb-xf86dri0
libxcb-xf86dri0-dev
libxcb-xfixes0-dev
libxcb-xinerama0-dev
libxcb-xinput-dev
libxcb-xkb-dev
libxcb-xrm0
libxcb-xrm-dev
libxcb-xtest0
libxcb-xtest0-dev
libxcb-xv0-dev
libxcb-xvmc0
libxcb-xvmc0-dev
libxext-dev
libxfixes-dev
libxi-dev
libxine2-bin
libxine2-dev
libxine2-ffmpeg
libxine2-misc-plugins
libxine2-plugins
libxkbcommon-dev
libxkbcommon-doc
libxkbcommon-tools
libxkbcommon-x11-dev
libxrender-dev
libfontconfig1-dev