[mutter/wip/carlosg/x11less-preparations: 15/26] core: Avoid grab transfer shenanigans with non-X11 backend

[Carlos Garnacho <carlosg src gnome org>]

commit 65d20d35dbfb5fe51ae42a4eae93cac0fd8142ea
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.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/420

 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 d36aaad8b..754d5a2e9 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;