Support for Python based Qt applications

[probonopd]

Can this also work with Python based Qt applications, such as https://github.com/Ultimaker/Cura/releases/download/4.2-beta/Ultimaker_Cura-4.2.0-BETA.AppImage?

[antony-jr]

I used on Pext and it worked but can't tell unless I try it.

[antony-jr]

Okay it did not work. Its weird. I will try to debug this.

[antony-jr]

One possible cause is mismatch of libqxcb Qt version. I don't know if I can fix this. Why can't we drop language independent and only support native applications? like applications built with c plus plus. I've also tried with Pext and it worked but I can't integrate the option into the menu. Maybe we need to do something else other than modifying the qt xcb plugin which is very elemental. I think we need to inject this into something high level.

[probonopd]

I'd really like to see Ultimaker Cura to get a self-updater built in, it's a really popular application.

[antony-jr]

I will try but I can't guarantee success.

[antony-jr]

Only this particular application is facing this problem. I compared the qxcb version and the pre-built version is just a single patch version old, So I hope this could work if we match the exact version?. I'm gonna try it later. I don't know if this could work.

This is the error I get,

QFactoryLoader::QFactoryLoader() looking at "/tmp/.mount_Cura-x51Gm0r/usr/bin/qt/plugins/platforms/libqxcb.so"
Found metadata in lib /tmp/.mount_Cura-x51Gm0r/usr/bin/qt/plugins/platforms/libqxcb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "xcb"
        ]
    },
    "className": "QXcbIntegrationPlugin",
    "debug": false,
    "version": 330240
}


Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/tmp/.mount_Cura-x51Gm0r/usr/bin/platforms" ...
Cannot load library /tmp/.mount_Cura-x51Gm0r/usr/bin/qt/plugins/platforms/libqxcb.so: (/tmp/.mount_Cura-x51Gm0r/usr/bin/libQt5Core.so.5: version `Qt_5.13' not found (required by /usr/lib/libQt5XcbQpa.so.5))
QLibraryPrivate::loadPlugin failed on "/tmp/.mount_Cura-x51Gm0r/usr/bin/qt/plugins/platforms/libqxcb.so" : "Cannot load library /tmp/.mount_Cura-x51Gm0r/usr/bin/qt/plugins/platforms/libqxcb.so: (/tmp/.mount_Cura-x51Gm0r/usr/bin/libQt5Core.so.5: version `Qt_5.13' not found (required by /usr/lib/libQt5XcbQpa.so.5))"

It looks like it uses the host system version of libQt5XcbQpa.so.5 even though it exists in the AppImage. When the qtxcb plugin is not replaced, everything just works fine.

[antony-jr]

So is this an AppImage error or the plugin. It seems like the plugin fails to load since it can't find libQt5XcbQpa.so.5 (built with Qt 5.10.1) from the system. Since the system will have my version of Qt which is 5.13.0, the load fails. But why this happens when I change the plugin? Maybe they are doing something wrong?

[antony-jr]

I tried the same on FreeCAD but the plugin does not do anything? But the application ran without any errors. Python is weird.

[antony-jr]

@probonopd Okay I found the problem. Its not with updatedeployqt or AppImages. Ultimate Cura simply packaged the Application wrong.
The plugin started working after I done the following changes...

Change the entry script like so,

#!/bin/sh

scriptdir=$(dirname $0)

export PYTHONPATH=$scriptdir/lib/python3.5
#export QT_PLUGIN_PATH=$scriptdir/qt/plugins
#export QML2_IMPORT_PATH=$scriptdir/qt/qml
export QT_QPA_FONTDIR=/usr/share/fonts
#export QT_XKB_CONFIG_ROOT=/usr/share/X11/xkb
export LD_LIBRARY_PATH="$scriptdir"
# Use the openssl.cnf packaged in the AppImage
export OPENSSL_CONF=$scriptdir/openssl.cnf

cura "$@"

Adding LD_LIBRARY_PATH is the key.

Add qt.conf.

[Paths]
Prefix = .
Plugins = qt/plugins
Imports = qml
Qml2Imports = qt/qml

And now it works. I think the major problem with python programs packaged with AppImages is that they are fundamentally broken in some way. Since we have no standard way of packaging python apps, Its really hard.

[antony-jr]

As expected, uses the same theme as the parent application...

[antony-jr]

One thing I can't figure out is integrating it into the menu. I can't search by text or id because its qml. I have to try a little harder.

[antony-jr]

Also on close the application crashes with

Segmentation fault      (core dumped) cura "$@"

Since its on close, it is not noticeable but I think Qt's parent to child de-allocation is the cause.

[antony-jr]

Hmm.. FreeCAD now works along with the plugin.

But the crash at end is still present, I think this is a bug in the plugin.

[antony-jr]

I'm thinking of removing the auto update feature entirely and force integrate with the menu instead.