Python Backend/QML Frontend Can I Convert To WebAssembly?

Edwin F.

I have only seen examples converting C++ Qt apps to WebAssembly using EMscripten. I have not seen anything converting Qt apps with a Python 'backend' to WebAssembly...

Are there any examples out there? Any tools available for this? For example an app like so with the following:

QML frontend:

main.qml

import QtQuick 2.12
import QtQuick.Window 2.2
import QtQuick.Controls 2.3


ApplicationWindow {
    id: window
    visible: true
    width: Screen.width
    height: Screen.height
    color: "white"
    
    Button {
        anchors.centerIn: parent
        onClicked: {
            backend.hi_from_qml('Nombre') 
        }

     }
}

And a Python "backend":

backend.py

from PySide2.QtCore import Qt, QObject, Signal, Slot, QCoreApplication
from PySide2.QtWidgets import QApplication
from PySide2.QtQml import QQmlApplicationEngine
import sys

class Backend(QObject):
	def __init__(self):
		QObject.__init__(self)

	@Slot(str)
	def hi_from_qml(self, name):
		print(f'Hi from qml: {name}')


if __name__ == '__main__':
    app = QApplication(sys.argv)
    engine = QQmlApplicationEngine()

    ctx = engine.rootContext()
    backend = Backend()    
    ctx.setContextProperty("backend", backend)    
    engine.load('main.qml')

    if not engine.rootObjects():
        sys.exit(-1)

    sys.exit(app.exec_())

One starts up the app like so from the terminal:

Ed-MacBook-Air:test$ python3 backend.py 
Hi from qml: Nombre

How would I convert this QML/Python app to Webassembly to serve through the browser? Any help would be greatly appreciated, I've been looking everywhere.

A possible but unfortunate workaround I'm thinking about in case this is not possible...Use PyBind11 as a thin 'C++ layer' between my existing QML frontend and my Python backend. And then compile that with EMscripten and be able to serve that, would that work?

Thanks!

Edwin F.

Is there anyone out there in the universe?! Anyone?! :)

SGaist

Hi,

Yes there is. Qt for WASM being pretty new, you will have to be more patient because there's currently likely not a lot of people using it here.

As for your question, I would say currently no.

This stack overflow answer will likely be of interest with regard to Python and WASM.

lorn.potter

I am unsure about python webassembly, but googling got me this:
https://almarklein.org/python_and_webassembly.html

Edwin F.

Thanks guys @SGaist and @lorn-potter

It seems like it is not really supported at this time and I will have to look into the alternative of putting a layer between the QML and Python backend in C++, essentially becomes a C++ app, but I only want to use C++ as a pass through to the Python somehow using PyBind11...I will try to see if that will work.