This application failed to start because it could not find or load the Qt platform plugin “xcb”

roroco

here is my stackoverflow question

this exist answer can not fix my question

In qt official example, I use following CMakeLists.txt

SET(CMAKE_PREFIX_PATH /media/roroco/disk750/Downloads/qtbase)
set(CMAKE_INCLUDE_CURRENT_DIR ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
find_package(Qt5Widgets)
find_library(xcb NAMES qxcb PATHS /media/roroco/disk750/Downloads/qtbase/plugins/platforms)
add_executable(systray main.cpp window.cpp systray.qrc)
target_link_libraries(systray Qt5::Widgets ${xcb})

and I get

This application failed to start because it could not find or load the Qt platform plugin "xcb".

How to add "xcb" plugin to cmake?

update

I'm sure find_library(xcb find the lib "/media/roroco/disk750/Downloads/qtbase/plugins/platforms/libqxcb.so".

update
when I add QApplication::addLibraryPath("/media/roroco/disk750/Downloads/qtbase/plugins");
and run again, I get:

This application failed to start because it could not find or load the Qt platform plugin "xcb".

Available platform plugins are: linuxfb, minimal, offscreen, xcb.

Reinstalling the application may fix this problem.

update
I try to add "LD_LIBRARY_PATH" like following in main.cpp, but still get error

    setenv("LD_LIBRARY_PATH", "/media/roroco/disk750/Downloads/qtbase/lib:/media/roroco/disk750/Downloads/qtbase/plugins", 1);
    QApplication::addLibraryPath("/media/roroco/disk750/Downloads/qtbase/plugins");

koahnig

@roroco

Hi and welcome to devnet

I suggest that you are posting the complete also here. It is good to have the link to your original post somewhere else. However, your link might after a while no longer helpful to others.

eureka

I had to troubleshoot this same xcb plugin problem when trying to run a third party app developed in Qt.

https://forum.qt.io/topic/64383/installed-app-cannot-find-or-load-plugin-xcb

And there are other threads in this forum if you just search 'xcb' ..

https://forum.qt.io/topic/64539/qt-5-5-app-deployment-on-ubuntu-14-04/4

As far as I understand (as a newcomer to Qt) LD_LIBRARY_PATH should just point to lib (not plugins as you have set)

In command line run .. qmake --version .. to get path to Qt lib.

When I run echo $LD_LIBRARY_PATH in command line I have
/opt/qt55/lib:/usr/lib/i386-linux-gnu/:/usr/lib/

(/opt/qt55 is my custom installation of Qt 5.5.1).

You can get plugin debug information by running your app in command line

QT_DEBUG_PLUGINS=1 myappname

or setting QT_DEBUG_PLUGINS=1 in environment.

I solved my problem by

(a) adding a qt.conf file to same location as app binaries (/usr/bin)

[Paths]
Prefix= ../../opt/qt55
Translations=i18n
Libraries=lib
Plugins=plugins

(b) adding Qt paths to ~/.profile

export PATH="/opt/qt55/bin":$PATH
export LD_LIBRARY_PATH="/opt/qt55/lib":${LD_LIBRARY_PATH}

There might be some redundancy in above steps I took by trial and error.