[mutter/wip/carlosg/xwayland-on-demand: 15/27] core: Avoid grab transfer shenanigans with non-X11 backend

[Carlos Garnacho <carlosg src gnome org>]

commit bb5a8ee0b7d300d2968843fb7503dd4fb771365d
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Dec 30 13:15:36 2018 +0100

    core: Avoid grab transfer shenanigans with non-X11 backend
    
    This explicit ungrab is made to ensure the other X11 display connection
    is able to start an active grab immediately on the device without receiving
    AlreadyGrabbed.
    
    This is just relevant if there's two X11 display connections to transfer
    grabs across, which may just happen on X11 windowing.

 src/core/display.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)
---
diff --git a/src/core/display.c b/src/core/display.c
index 94982b0da..817116f64 100644
--- a/src/core/display.c
+++ b/src/core/display.c
@@ -1677,14 +1677,17 @@ meta_display_begin_grab_op (MetaDisplay *display,
   if (pointer_already_grabbed)
     display->grab_have_pointer = TRUE;
 
-  /* Since grab operations often happen as a result of implicit
-   * pointer operations on the display X11 connection, we need
-   * to ungrab here to ensure that the backend's X11 can take
-   * the device grab. */
-  XIUngrabDevice (display->x11_display->xdisplay,
-                  META_VIRTUAL_CORE_POINTER_ID,
-                  timestamp);
-  XSync (display->x11_display->xdisplay, False);
+  if (META_IS_BACKEND_X11 (meta_get_backend ()) && display->x11_display)
+    {
+      /* Since grab operations often happen as a result of implicit
+       * pointer operations on the display X11 connection, we need
+       * to ungrab here to ensure that the backend's X11 can take
+       * the device grab. */
+      XIUngrabDevice (display->x11_display->xdisplay,
+                      META_VIRTUAL_CORE_POINTER_ID,
+                      timestamp);
+      XSync (display->x11_display->xdisplay, False);
+    }
 
   if (meta_backend_grab_device (backend, META_VIRTUAL_CORE_POINTER_ID, timestamp))
     display->grab_have_pointer = TRUE;