Joachim Breitner writes:
I didn’t try it, because at the moment I don’t have a second screen, but from what I read, I’m unsure if it’s a good idea.
Not having windows that are not on the current workspace show up in window lists is a bad idea, as more than just a workspace switcher relies on that (window lists, and even unrelated tools like my arbtt, need to have all windows in _NET_CLIENT_LIST).
(but maybe I’m misunderstanding your patch)
I don't mess with _NET_CLIENT_LIST, it still reports all windows. If you have two monitors, and they're pointing at workspaces 1 and 2, with 1 being active and 2 merely visible, my patch reports the windows on 1 as belonging to workspace 1 (the active workspace) and the windows on 2 as belonging to workspace 2. The previous behaviour had all visible windows (those from both 1 and 2) reported as being on workspace 1, so that they'd all be on the active workspace (since EWMH has no concept of two workspaces being visible at once)