Check when load picture/htm finished

My app reads pictures and web-links.
I need a way to check

  1. to add a progress bar so the user to know when the upload finishes each file uploaded…
  2. to add a progress bar so the pixture/html viewer to show its contents…

Is there any waybto count the bytes of the file being uploaded? Or the picture file being loaded in the picture viewer?

Are there any suggestions? I use xojocloud and it usually it is a bit slow, so the needs to know what is going on
Thanks in advance

The webfileuploader in 2018r1 has progress events.

This is nice but i have read that this version has some other issues and i am hesitated to work with.
Any tip to make visible the picture viewer when the new picture is ready for viewing. I understand that when i want to show a picture from the server it should be «downloaded» first. In memory…or can i use its URL?