device: Use standard grabs for passive button grabs

Bug: 16347

XInput2 passive button grab would not fail if the button is already
grabbed by the client.

X-AIR-Edit is such a client which issues a button grab on its own
window, meaning that with XI2 button it would not react to button events
anymore.

Revert to the standard grab button for the passive grabs so that such
apps can still work with xfwm4.

Signed-off-by: Olivier Fourdan <fourdan@xfce.org>

src/device.c

@@ -402,59 +402,20 @@ xfwm_device_grab_button (XfwmDevices *devices, Display *display,
                          gint grab_mode, gint paired_device_mode,
                          Window confine_to, Cursor cursor)
 {
-    gboolean result;
-    Status status;
-#ifdef HAVE_XI2
-    XIGrabModifiers xi2_modifiers;
-    XIEventMask xievent_mask;
-#endif
+    gboolean status;
 
-#ifdef HAVE_XI2
-    if (devices->xi2_available)
-    {
-        xi2_modifiers.modifiers = xi2_modifier_mask (modifiers);
-        xi2_modifiers.status = 0;
+    status = XGrabButton (display, button, modifiers, grab_window,
+                          owner_events, event_mask, grab_mode, paired_device_mode,
+                          confine_to, cursor);
 
-        xfwm_device_fill_xi2_event_mask (&xievent_mask, event_mask);
-        status = XIGrabButton (display, devices->pointer.xi2_device, button, grab_window,
-                               cursor, grab_mode, paired_device_mode, owner_events,
-                               &xievent_mask, 1, &xi2_modifiers);
-        g_free (xievent_mask.mask);
-        result = (status == XIGrabSuccess);
-    }
-    else
-#endif
-    {
-        status = XGrabButton (display, button, modifiers, grab_window,
-                              owner_events, event_mask, grab_mode, paired_device_mode,
-                              confine_to, cursor);
-        result = (status == GrabSuccess);
-    }
-    return result;
+    return status;
 }
 
 void
 xfwm_device_ungrab_button (XfwmDevices *devices, Display *display,
                            guint button, guint modifiers, Window grab_window)
 {
-#ifdef HAVE_XI2
-    XIGrabModifiers xi2_modifiers;
-#endif
-
-#ifdef HAVE_XI2
-    if (devices->xi2_available)
-    {
-        xi2_modifiers.modifiers = xi2_modifier_mask (modifiers);
-        xi2_modifiers.status = 0;
-
-        XIUngrabButton (display, devices->pointer.xi2_device, button,
-                        grab_window, 1, &xi2_modifiers);
-    }
-    else
-#endif
-    {
-        XUngrabButton (display, button, modifiers, grab_window);
-    }
+    XUngrabButton (display, button, modifiers, grab_window);
 }
 
 gboolean