How do I get the active window on Gnome Wayland?

The two previous answers are outdated, this is the current state of querying appnames and titles of windows in (Gnome) Wayland.

1. A Gnome-specific JavaScript API which can be accessed over DBus
2. The wlr-foreign-toplevel-management Wayland protocol (unfortunately not implemented by Gnome)

The Gnome-specific API will likely break between Gnome versions, but it works. It is heavily dependent on Gnome internal API to work so there is no chance of it becoming a standard API. There is a PR on aw-watcher-window to add this, but it needs some clean-up and afk-support if that's possible.

The wlr-foreign-toplevel-management protocol is (at the time of writing this) implemented by the Sway, Mir, Phosh and Wayfire compositors. Together with the idle.xml protocol which is pretty widely implemented by wayland compositors there's a complete implementation with afk-detection for ActivityWatch in aw-watcher-window-wayland. I've been in discussions with sway/rootston developers about whether wayland appnames and X11 wm_class is interchangeable and both Sway and Phosh use these interchangeably now so there should no longer be any distinguishable differences between Wayland and XWayland windows in the API anymore.

I have not researched if KWin has some API similar to Gnome Shell to fetch appnames and titles, but it does at least not implement wlr-foreign-toplevel-management.

In my opinion the best choice you have is not Wayland or any available library (there are not one). Actually who know in gnome-wayland about the active windows is Mutter, so you need to find a way to ask to Mutter the active windows. Gnome can develop an API to internally ask to mutter the active window and restore the functionality. But really, you don't have a place to ask for it. Mutter will not develop an API to access to his internal representation, because this will be pretty specific of Mutter only and not to all Wayland windows manager. So this need to be added to an external library, where this library could talk probably with the current window manager that it's in use to resolve your request in a general way.

Another possibility is add a Wayland plugin where all windows manager will have a way to share the current active windows and in some way a library to talk directly with wayland to restore the functionality.

So, your app is in a big problem. Most you can do is request this on mutter (where is know the active windows), but in my opinion it can not be resolved in Mutter.

I hope this will help you and you can find a way. Good luck.

I have a script called preguiça.py, that does exactly what you're doing, though it is probably a lot simpler and I haven't released it.

For my script, I acquired the window title using PyGObject's Window Navigator Construction Kit (Wnck).

Here's a simplified version of it, with the essencial parts:

from gi.repository import Wnckfrom gi.repository import GObjectdef changed (screen, window, data):    print ("Changed!")#    window = screen.get_active_window()    if window:        print ("Title: %s" % window.get_name())screen = Wnck.Screen.get_default ()screen.connect ("active-window-changed", changed, None)mainLoop = GObject.MainLoop ()try:    mainLoop.run ()except KeyboardInterrupt:    print ("Hey")mainLoop.unref ()

The actual code for what you're asking is actually commented out on the example above (I didn't need to capture the window, as the callback already receives it), but you may need it depending on your implementation.

I wrote it for X, and it didn't complain when I switched to Wayland, so it should probably work for you.

Note it doesn't get the information from Wayland, as you asked, but it is probably actually better, as it will be X/Wayland-agnostic. It got the title from an xterm I opened, so it should be toolkit-agnostic, as well.

Don't ask me on the details of the implementation, though. The code is at least four years old :)