#wlr-toplevel-monitor

Wayland client that uses the wlr-foreign-toplevel-management protocol to monitor the currently active toplevel surface and continuously writes a single line with its identifier and title to standard output every time it changes.

This can be used in combination with Eww's deflisten to show the active toplevel in a widget. For example:

(deflisten toplevel "wlr-toplevel-monitor")
(defwindow toplevel-bar
  :monitor 0
  :stacking "fg"
  :reserve (struts :distance "26px" :side "top")
  :geometry (geometry :height "26px" :anchor "top center")
  (label :text toplevel))