Improve recovery after reconnecting

[rodja]

This pull request tries to implement #1761.

[falkoschindler]

@rodja I just tested the implementation with a simple test app:

from nicegui import ui

ui.input('Hello world!')
ui.button('Click me!', on_click=lambda: ui.notify('Button clicked!'))

ui.run(reconnect_timeout=10.0)

When I type something into the input field, disconnect the connection via developer tools > network > throttling, wait for the connection popup and reconnect, the input is preserved. But the same happens for reconnect_timeout = 0. Shouldn't this trigger a reload?

[falkoschindler]

Sorry, my bad: reconnect_timeout has no effect on the auto-index client. 🤦🏻‍♂️

[falkoschindler]

@rodja I just got aware of a possibly inconvenient behavior when using reconnect_timeout = 3 (the new default in version 1.4):

@ui.page('/test')
async def page(client: Client):
    ui.label('Hello, world!')
    await client.disconnected()
    print('disconnected', flush=True)

The client.disconnected will only return after 3 seconds. Although this is correct and consistent, it might lead to unexpected delays when transitioning to version 1.4.

[rodja]

@falkoschindler yes, that's why I chose to use 0 for 1.3. But allowing clients to reconnect without page reload is super important and I would gladly trade the delayed client.disconnected() for the benefit of reducing state loss.