A small demo of using pywebview with NiceGUI based on wrapping both Unicorn.Server and webview in processes.

nicegui_webview_demo.py

#!/usr/bin/env python3
import multiprocessing
import tempfile

from fastapi import FastAPI
from uvicorn import Config, Server
import webview

from nicegui import ui


class UvicornServer(multiprocessing.Process):

    def __init__(self, config: Config):
        super().__init__()
        self.server = Server(config=config)
        self.config = config

    def stop(self):
        self.terminate()

    def run(self, *args, **kwargs):
        self.server.run()


def start_window(pipe_send, url_to_load):
    def on_closed():
        pipe_send.send('closed')

    win = webview.create_window('Demo', url=url_to_load)
    win.events.closed += on_closed
    webview.start(storage_path=tempfile.mkdtemp())
    
    
app = FastAPI()


@app.get('/')
def read_root():
    return {'Hello': 'World'}


@ui.page('/show')
def show():
    ui.image('https://picsum.photos/id/377/640/360')


ui.run_with(app)


if __name__ == '__main__':
    server_ip = "127.0.0.1"
    server_port = 8080
    conn_recv, conn_send = multiprocessing.Pipe()

    windowsp = multiprocessing.Process(target=start_window, args=(conn_send, f'http://{server_ip}:{server_port}/show'))
    windowsp.start()

    config = Config("main:app", host=server_ip, port=server_port, log_level="debug")
    instance = UvicornServer(config=config)
    instance.start()

    window_status = ''
    while 'closed' not in window_status:
        # get a unit of work
        window_status = conn_recv.recv()
        # report
        print(f'got {window_status}', flush=True)

    instance.stop()

I'll have to check that out. I want to run_with an own FastAPI app in native mode, but this gist so far was the only code I found that achieves that. Dont get me wrong, this could be a lot easier. But it's not there yet in NiceGUI directly as far as I can tell.