I am making ProgrssUI - set of tools to track processes tasks, show progress/status and allow to set actions to be fired on specified task internal state, for example status.

Imagine you would like to set shutdown action on download done with success or beep sound when there is an error, when downloading. You do not need specialized software for this purpose. You only need software, which inform my daemon about progress/status. It is more probably Firefox developers integrate web browser with my solution or there will some extension been made than software for each use case could been created.

I will made it as simple as possible. You must type command (program name with parameters) if created action run external tool. In future I will add parsing .desktop files, so user could select program. Maybe I will add manual viewer? Also, I think I should add DBus integration: there could exist special interface with CallUserAction method, which programs could implement; programs could register action, parameters of registered actions and description in many languages. Maybe I will add type system to made think easier - for example how old something/someone is, file, number, etc.?

Most interesting it worked in some part.
You can see how it work on: https://www.youtube.com/watch?v=sm04e2N5AcU&t=58s
Blog post: https://nintyfan.wordpress.com/2021/06/16/progressui/

If you can, donate or help in development. Most important is adding integration to as many programs as we can.

Sourceforge.net page: https://sourceforge.net/projects/progresui/ . You can download sources from there. It requires libgreattao (from master) and libdbus-1.

https://www.patreon.com/posts/progressui-with-52843791

https://www.youtube.com/watch?v=kX2Yw2opvgg

Firefox integration.