How to turn on progressbar early for liveview form submission?

According to phoenix doc:

For live page navigation via live_redirect and live_patch, as well as form submits via phx-submit, the JavaScript events "phx:page-loading-start" and "phx:page-loading-stop" are dispatched on window.

And I can use the 2 events to turn on and off onebar nicely. However, for form submission that invlolve password update, there is some non-negligible time spent on password hashing in Argon2. During this time, the progressbar is not showing. It may confuse my user. How can I somehow turn on the progressbar earlier, like as soon as the form submission is triggered?

Sorry, I messed up my progress bar. Phoenix already has the the behavior that I need. Neat.