[d-feet] Assume Wnck is absent on non-X11

[Thomas Bechtold <toabctl src gnome org>]

commit ad26a1b7d1b66d6a5bda269b1e0291110cc0fc14
Author: Debarshi Ray <debarshir gnome org>
Date:   Tue Jun 6 16:13:45 2017 +0200

    Assume Wnck is absent on non-X11
    
    Wnck is an X11-only API. While Wnck.Screen.get_default() might have
    elegantly returned None in the absence of X11 earlier, we cannot rely
    on that behaviour. In fact, the same version of libwnck has started to
    crash inside Wnck.Screen.get_default().
    
    Let's not touch Wnck when X11 is absent.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=763615

 src/dfeet/wnck_utils.py |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)
---
diff --git a/src/dfeet/wnck_utils.py b/src/dfeet/wnck_utils.py
index 2ba68a6..9d103ef 100644
--- a/src/dfeet/wnck_utils.py
+++ b/src/dfeet/wnck_utils.py
@@ -4,9 +4,15 @@
 # behvior
 
 import gi
-from gi.repository import Gtk
+from gi.repository import Gtk, Gdk, GLib
+
+def running_in_x11():
+    display = Gdk.Display.get_default()
+    return display.__gtype__.name == 'GdkX11Display'
 
 try:
+    if not running_in_x11():
+        raise GLib.Error('Wnck is only meant to be used with X11')
     gi.require_version('Wnck', '3.0')
     from gi.repository import Wnck
     has_libwnck = True
@@ -26,7 +32,6 @@ class IconTable(object):
 
         if has_libwnck:
             screen = Wnck.Screen.get_default()
-            # screen is None under Wayland
             if screen is not None:
                 Wnck.Screen.force_update(screen)
                 screen.connect('application_opened', self.on_app_open)