How do I detect the currently focused application?

Question

I'd like to be able to track which application is currently focused on my X11 display from Python. The intent is to tie it into a timetracking tool so that I can keep track of how much time I spend being unproductive.

I already found this code at http://thpinfo.com/2007/09/x11-idle-time-and-focused-window-in.html:

import Xlib.display
display = Xlib.display.Display()
focus = display.get_input_focus()
print "WM Class: %s" % ( focus.focus.get_wm_class(), )
print "WM Name: %s" % ( focus.focus.get_wm_name(), )

However, it doesn't seem to work for me. Apparently, no matter which application is focused, both get_wm_class() and get_wm_name() just return None.

Of course the solution needs to work with all these new fangled window managers like Compiz and such.

Answer 1

Whoo! I figured it out myself:

import Xlib.display
display = Xlib.display.Display()
window = display.get_input_focus().focus
wmname = window.get_wm_name()
wmclass = window.get_wm_class()
if wmclass is None and wmname is None:
    window = window.query_tree().parent
    wmname = window.get_wm_name()
print "WM Name: %s" % ( wmname, )

Answer 2

A somewhat nicer solution, especially for a long-running app rather than a script, would use libwnck to track the _NET_ACTIVE_WINDOW hint. (See the EWMH specification for the definition of the hint.)