How is the blue topic progress bar in this forum implemented?

Hi, I’d like my app to react to the component currently viewed by the user in a scrollable page: as the user scrolls down and sees new components, callbacks are fired.

In fact it seems like what I’m looking for is pretty close to the little topic progress bar that will appear just here at the bottom right side of this page if someone (hopefully!) answers this question! Is it written in Dash? Could someone suggest how to create such a thing?

Ideally I’d like to hide many little Divs along the long page and have them trigger different callbacks as the user scrolls down.

I’d appreciate any idea, thanks!

This forum uses the discourse software, which is open source if you want to take a look. You can also inspect the different elements of the page using the dev tools of your browser.


Thanks @Emmanuelle. And now the question is, is it possible to implement it with Dash?