Switching workspaces sometimes does not focus the sole X window there?

[BettaGeorge]

Not sure whether to open an issue for this since I do not even know how to reliably reproduce it. Do others have this same problem?

Essentially, when I switch to a workspace with just one X window in it and nothing else, sometimes that X window does not get focus. I notice this mostly with the Spotify client for Linux, since it is a natural action to switch there and press space bar to pause the song, which usually works, but not always. Since (other-window) does not work when there is only one window, the only way to get the window in focus is to actually move the mouse there and click, which is not something I want to do. (Okay, technically I could also split the frame and then unsplit it.)

Does this only happen in my configuration? I do not have focus-follows-mouse enabled, nor configured anything else focus-related. It happens on a fresh install of EXWM with just (hopefully unrelated) Helm config and some workspaces assigned to monitors via exwm-randr.

Edit: I just experimented a bit, and it seems to happen rather arbitrarily. It only happens when switching from a workspace with a sole Emacs buffer to a workspace with a sole X window, never when going from X window to X window. When going from an Emacs workspace to my Spotify workspace, about half the time the focus is set correctly, and about half the time it is not. The fun thing is that I have no other interaction in between. Literally only using s-1 and s-2 (bound to exwm-workspace-switch-create 1 and exwm-workspace-switch-create 2) and SPC (on the Spotify workspace, to try whether the window is in focus), I am able to randomly (?) switch between Spotify being in focus and being not in focus. Nothing else appears to be in focus when the X window is not; at least I can never see any input having any effect.

[Stebalien]

This is a bug #163.

NOTE: Spotify is an electron app, which is based on chrome.