Background: I'm working on a piece of software called ActivityWatch that logs what you do on your computer. Basically an attempt at addressing some of the issues with: RescueTime, selfspy, arbtt, etc.
One of the core things we do is log information about the active window (class and title). In the past, this has been done using on Linux using xprop and now python-xlib without issue.
But now we have a problem: Wayland is on the rise, and as far as I can see Wayland has no notion of an active window. So my fear is that we will have to implement support for each and every desktop environment available for Wayland (assuming they'll provide the capability to get information about the active window at all).
Hopefully they'll eventually converge and have some common interface to get this done, but I'm not holding my breath...
I've been anticipating this issue. But today we got our first user request for Wayland support by an actual Wayland user. As larger distros are adopting Wayland as the default display server protocol (Fedora 25 is already using it, Ubuntu will switch in 17.10 which is coming soon) the situation is going to get more critical over time.
Relevant issues for ActivityWatch:
There are other applications like ActivityWatch that would require the same functionality (RescueTime, arbtt, selfspy, etc.), they don't seem to support Wayland right now and I can't find any details about them planning to do so.
I'm now interested in implementing support for Gnome to start off with and follow up with others as the path becomes more clear.
A similar question concerning Weston has been asked here: get the list of active windows in wayland weston
Edit: I asked in #wayland on Freenode, got the following reply:
15:20:44 ErikBjare Hello everybody. I'm working on a piece of self-tracking software called ActivityWatch (https://github.com/ActivityWatch/activitywatch). I know this isn't exactly the right place to ask, but I was wondering if anyone knew anything about getting the active window in any Wayland-using DE.
15:20:57 ErikBjare Created a question on SO: https://stackoverflow.com/questions/45465016/how-do-i-get-the-active-window-on-gnome-wayland
15:21:25 ErikBjare Here's the issue in my repo for it: https://github.com/ActivityWatch/activitywatch/issues/92
15:22:54 ErikBjare There are a bunch of other applications that depend on it (RescueTime, selfspy, arbtt, ulogme, etc.) so they'd need it as well
15:24:23 blocage ErikBjare, in the core protocol you cannot know which windnow has the keyboard or cursor focus
15:24:39 blocage ErikBjare, in the wayland core protocol *
15:25:10 blocage ErikBjare, you can just know if your window has the focus or not, it a design choise
15:25:23 blocage avoid client spying each other
15:25:25 ErikBjare blocage: I'm aware, that's my reason for concern. I'm not saying it should be included or anything, but as it looks now every DE would need to implement it themselves if these kind of applications are to be supported
15:25:46 ErikBjare So wondering if anyone knew the teams working with Wayland on Gnome for example
15:26:11 ErikBjare But thanks for confirming
15:26:29 blocage ErikBjare, DE should create a custom extension, or use D-bus or other IPC
15:27:31 blocage ErikBjare, I guess some compositor are around here, but I do not know myself if there is such extension already
15:27:44 blocage compositor developers *
15:28:36 ErikBjare I don't think there is (I've done quite a bit of searching), so I guess I need to catch the attention of some DE developers
15:29:16 ErikBjare Thanks a lot though
15:29:42 ErikBjare blocage: Would you mind if I shared logs of our conversation in the issue?
15:30:05 blocage just use it :) it's public
15:30:19 ErikBjare ty :)
Edit 2: Filed an enhancement issue in the Gnome bugtracker.
tl;dr: How do I get the active window on Gnome when using Wayland?
The two previous answers are outdated, this is the current state of querying appnames and titles of windows in (Gnome) Wayland.
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.