I am trying to use Qt 6.3 or later in a classic core22 snap:
name: qt-snap-test
title: Qt SNAP test
version: "1.0"
base: core22
summary: Qt SNAP test
description: test snap for Qt
grade: stable
confinement: classic
parts:
qt:
source: http://code.qt.io/qt/qt5.git
# source-tag: "v6.2.4"
source-tag: "v6.3.0"
source-depth: 1
source-submodules: [qtbase,qtwayland]
plugin: cmake
cmake-generator: Ninja
build-attributes:
- enable-patchelf
cmake-parameters:
- -DCMAKE_INSTALL_PREFIX=/
build-packages:
- libegl-dev
- libgl-dev
- libharfbuzz-dev
- libjpeg-dev
- libpng-dev
- libvulkan-dev
- libwayland-dev
# xcb QPA (Qt Platform Abstraction) platform plugin
- libfontconfig1-dev
- libfreetype6-dev
- libx11-dev
- libx11-xcb-dev
- libxext-dev
- libxfixes-dev
- libxi-dev
- libxrender-dev
- libxcb1-dev
- libxcb-glx0-dev
- libxcb-keysyms1-dev
- libxcb-image0-dev
- libxcb-shm0-dev
- libxcb-icccm4-dev
- libxcb-sync-dev
- libxcb-xfixes0-dev
- libxcb-shape0-dev
- libxcb-randr0-dev
- libxcb-render-util0-dev
- libxkbcommon-dev
- libxkbcommon-x11-dev
stage-packages:
- libegl1
- libfontconfig1
- libfreetype6
- libgl1
- libglvnd0
- libglx0
- libgraphite2-3
- libharfbuzz0b
- libjpeg-turbo8
- libpcre2-16-0
- libpng16-16
- libwayland-cursor0
- libwayland-egl1
- libx11-6
- libx11-xcb1
- libxau6
- libxcb-glx0
- libxcb-icccm4
- libxcb-image0
- libxcb-keysyms1
- libxcb-randr0
- libxcb-render-util0
- libxcb-render0
- libxcb-shape0
- libxcb-shm0
- libxcb-sync1
- libxcb-util1
- libxcb-xfixes0
- libxcb-xkb1
- libxcb1
- libxdmcp6
- libxkbcommon-x11-0
- libxkbcommon0
mini-cmake-qt:
after: [qt]
source: https://github.com/euler0/mini-cmake-qt.git
source-branch: main
source-depth: 1
plugin: cmake
cmake-generator: Ninja
build-attributes:
- enable-patchelf
cmake-parameters:
- -DCMAKE_INSTALL_PREFIX=/
apps:
qt-snap-test:
command: bin/example
environment:
QT_QPA_PLATFORM: wayland;xcb
But when I start this snap, it cannot recognise the platform plugins (wayland, xcb, …):
qt.qpa.plugin: Could not find the Qt platform plugin "wayland" in ""
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.
Abgebrochen (Speicherabzug geschrieben)
Debugging this with QT_DEBUG_PLUGINS=1 qt-snap-test shows that it cannot read the metadata from the shared object plugin files:
qt.core.plugin.factoryloader: looking at "/snap/qt-snap-test/x1/plugins/platforms/libqxcb.so"
qt.core.plugin.loader: Failed to find metadata in lib /snap/qt-snap-test/x1/plugins/platforms/libqxcb.so: '/snap/qt-snap-test/x1/plugins/platforms/libqxcb.so' is not a Qt plugin (metadata not found)
qt.core.plugin.factoryloader: "Failed to extract plugin meta data from '/snap/qt-snap-test/x1/plugins/platforms/libqxcb.so': '/snap/qt-snap-test/x1/plugins/platforms/libqxcb.so' is not a Qt plugin (metadata not found)"
not a plugin
This used to work with Qt 6.2.4 but it fails with Qt 6.3 and upwards.
It appears that “patchelf” is removing the metadata of the plugins. I wrote a small program to show the Qt plugin metadata: https://github.com/christianrauch/qt_plugin_metadata/blob/main/main.cpp. This project hast to be compiled with a Qt version that is equal or greater than the version of the Qt plugin; in this case Qt 6.3.
Running this program with the XCB plugin (/snap/qt-snap-test/current/plugins/platforms/libqxcb.so) for different snapcraft variations shows that the metadata is missing for some snapcraft configurations.
For source-tag: "v6.2.4" with enable-patchelf:
has metadata?: YES
IID : org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3
MetaData : <Object>
archlevel : 0.000000
className : QXcbIntegrationPlugin
debug : False
version : 393728.000000
For source-tag: "v6.3.0" with enable-patchelf:
has metadata?: NO
And for source-tag: "v6.3.0" without enable-patchelf:
has metadata?: YES
IID : org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3
MetaData : <Object>
archlevel : 1.000000
className : QXcbIntegrationPlugin
debug : False
version : 393984.000000
However, without enable-patchelf the snap will not run because of wrong rpaths etc.
How do I prevent snapcraft to remove the metadata of the Qt plugins with enable-patchelf?