Question about hotkey icons in screen

When I press hotkey icon from notebook keyboard like brightness up/down, volume mute/up/down etc, there is icon with progress bar shown on screen in a couple of seconds.

My question is which gnome packages have the code about implementation of the icon with progress bar on screen. (I suppose it is done in user space?)

I found in gnome-shell, there is some code relate to volume mute/up/down etc from setting or application menus. But it seems like it has nothing to do with the hotkey icon on screen.


Thanks!