The on_change event of ui.input is stuck in a loop

[CrystalWindSnake]

Description

This issue seems to be quite serious.

from nicegui import ui
from time import sleep

count = 0

def onchange():
    global count
    count += 1
    print("onchage:", count)
    sleep(1)
    input1.update()

input1 = ui.input(on_change=onchange)

ui.run()

continuously enter the letter 'd' in the input box. The console can see that the on_change event is triggered repeatedly.

[falkoschindler]

Thanks for reporting this bug, @CrystalWindSnake!

First I have to say: Event handlers should not block code execution for so long. Sleeping synchronously for 1 second will freeze the UI. Expensive computations should run in an executor.

But there are certainly scenarios where change events come in very frequently and processing might take a bit too long. Then, of course, the displayed value should not oscillate. So this issue is totally valid.

I think I could fix it in 1c30ef1 by disabling change events while processing an update from the server.