master 227f3842c2: Reduce syncing when fetching selection names during frame deletion

[Po Lu]

branch: master
commit 227f3842c29f1991388ce518645baac412cf1f56
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Reduce syncing when fetching selection names during frame deletion
    
    * src/xterm.c (x_preserve_selections): Use XCB to asynchronously
    fetch the selection owner.
---
 src/xterm.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/xterm.c b/src/xterm.c
index a13162d61b..6e3a941719 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -27964,6 +27964,11 @@ x_preserve_selections (struct x_display_info *dpyinfo, 
Lisp_Object lost)
   Atom *names;
   ptrdiff_t nowners, counter;
   struct selection_input_event clear;
+#ifdef USE_XCB
+  xcb_get_selection_owner_cookie_t *cookies;
+  xcb_generic_error_t *error;
+  xcb_get_selection_owner_reply_t *reply;
+#endif
 
   new_owner = Qnil;
 
@@ -28006,6 +28011,9 @@ x_preserve_selections (struct x_display_info *dpyinfo, 
Lisp_Object lost)
     {
       owners = alloca (sizeof *owners * nowners);
       names = alloca (sizeof *names * nowners);
+#ifdef USE_XCB
+      cookies = alloca (sizeof *cookies * nowners);
+#endif
 
       tail = lost;
       nowners = 0;
@@ -28018,8 +28026,30 @@ x_preserve_selections (struct x_display_info *dpyinfo, 
Lisp_Object lost)
          /* Now check if we still don't own that selection, which can
             happen if another program set itself as the owner.  */
          names[counter++] = symbol_to_x_atom (dpyinfo, XCAR (tem));
+
+#ifndef USE_XCB
          owners[nowners++] = XGetSelectionOwner (dpyinfo->display,
                                                  names[counter - 1]);
+#else
+         cookies[nowners++]
+           = xcb_get_selection_owner (dpyinfo->xcb_connection,
+                                      names[counter - 1]);
+       }
+
+      nowners = 0;
+
+      FOR_EACH_TAIL_SAFE (tail)
+       {
+         reply = xcb_get_selection_owner_reply (dpyinfo->xcb_connection,
+                                                cookies[nowners++], &error);
+
+         if (reply)
+           owners[nowners - 1] = reply->owner;
+         else
+           owners[nowners - 1] = None;
+
+         free (reply ? (void *) reply : (void *) error);
+#endif
 
          if (owners[nowners - 1] != FRAME_X_WINDOW (XFRAME (new_owner)))
            {