Pyside2 over LinuxFB/DRM

JimJin

We are using PySide2 on our embedded Linux board, the hardware does not contain GPU (and no X11). So we have to use LinuxFB/DRM. The Qt for C++ works well. We set the correct environment variables:

export QT_QPA_FB_TSLIB=1

export QT_ROOT=/data/QT5/arm-qt
export QT_QPA_FONTDIR=$QT_ROOT/fonts/truetype/freefont
export QT_QPA_PLATFORM_PLUGIN_PATH=$QT_ROOT/plugins
export QT_PLUGIN_PATH=$QT_ROOT/plugins
export LD_LIBRARY_PATH=$QT_ROOT/lib:$QT_ROOT/plugins/platforms
export QT_QPA_PLATFORM=linuxfb
export QT_QPA_FB_DRM=1

After downloading PySide2(from https://archlinuxarm.org/packages/aarch64/pyside2), we run a python sample and it complains ImportError: /data/usr/lib/python3.9/site-packages/PySide2/QtWidgets.cpython-39-aarch64-linux-gnu.so: undefined symbol: _ZTI13QOpenGLWidget, version Qt_5.

Does it mean that PySide2 (or shiboken2) didn't use LinuxFB/DRM? Is there any way to switch to LinuxFB/DRM without recompiling PySide2?

SGaist

Hi and welcome to devnet,

Does your Qt library come from the same source as PySide2 ?

Does your example use QOpenGLWidget ?

JimJin

Does your Qt library come from the same source as PySide2 ?

No.

Does your example use QOpenGLWidget ?

No.

Looking forward to your help. Thanks in advance.

SGaist

@JimJin said in Pyside2 over LinuxFB/DRM:

Does your Qt library come from the same source as PySide2 ?

No

Then you should ensure it does.

PySide2 is built against a set of libraries that provides all the classes exposed as Python classes. You seem to use a version of Qt that is lighter weight.

JimJin

Then you should ensure it does.

Sure. We are going to do it.

You seem to use a version of Qt that is lighter weight.

Yes. We are using Qt Embedded. However, we can't find the manual of compiling PySide2 on ARM. Could you please show us a link of a porting guide to ARM?

SGaist

What are you using to cross-compile Qt ?

wonghui

@SGaist said in Pyside2 over LinuxFB/DRM:

What are you using to cross-compile Qt ?

We are using linaro-gcc (aarch64-linux-gnu)

JimJin

@JimJin said in Pyside2 over LinuxFB/DRM:

Does your Qt library come from the same source as PySide2 ?

Is it possible to hack PySide2 binaries(from https://archlinuxarm.org/packages/aarch64/pyside2) which redirect OpenGL to LinuxFB?

SGaist

You are mixing two different things. The backend plugin is not the issue.

Your issue is that you are trying to use a version of PySide2 that was built against a version of Qt with OpenGL enable and thus using the corresponding symbols with a version of Qt with OpenGL disabled as it seems.

JimJin

Your issue is that you are trying to use a version of PySide2 that was built against a version of Qt with OpenGL enable and thus using the corresponding symbols with a version of Qt with OpenGL disabled as it seems.

Yes, exactly. So,

Is there any hack(or workaround) to let the PySide2 of OpenGL work on QT of LinuxFB?
Or, is there any manual (or article) to guide us to cross-compile PySide2 on embedded Linux?

SGaist

@JimJin said in Pyside2 over LinuxFB/DRM:

Is there any hack(or workaround) to let the PySide2 of OpenGL work on QT of LinuxFB?

As I already wrote several times: your issue is unrelated to mixing OpenGL and LinuxFB

@JimJin said in Pyside2 over LinuxFB/DRM:

Or, is there any manual (or article) to guide us to cross-compile PySide2 on embedded Linux?

I am not aware of any but since it's a Qt project following the documentation:

python setup.py build --qmake=/path/to/your-cross-compiled-Qt/bin/qmake --ignore-git --parallel=8

might be enough.

JimJin

@SGaist Thank you very much. I'll try it ASAP and keep you posted.

wonghui

@SGaist Is there an option to disable opengl when build pyside2?

SGaist

I do not think there's anything special to do as long as you use a Qt version that was built with OpenGL disabled but that's only a guess.