Avoid unnecessary focus changes when creating/killing buffers

* exwm-input.el (exwm-input--skip-buffer-list-update): New internal
variable for skipping the next 'buffer-list-update'.
(exwm-input--on-buffer-list-update): Skip when
`exwm-input--skip-buffer-list-update` is set.

* exwm-manage.el (exwm-manage--manage-window): Set
`exwm-input--skip-buffer-list-update` when creating/killing buffers.

exwm-input.el

@@ -117,6 +117,9 @@ defined in `exwm-mode-map' here."
 
 (defvar exwm-input--simulation-keys nil "Simulation keys in line-mode.")
 
+(defvar exwm-input--skip-buffer-list-update nil
+  "Skip the upcoming 'buffer-list-update'.")
+
 (defvar exwm-input--temp-line-mode nil
   "Non-nil indicates it's in temporary line-mode for char-mode.")
 
@@ -264,6 +267,7 @@ ARGS are additional arguments to CALLBACK."
 (defun exwm-input--on-buffer-list-update ()
   "Run in `buffer-list-update-hook' to track input focus."
   (when (and (not (eq this-command #'handle-switch-frame))
+             (not exwm-input--skip-buffer-list-update)
              (not (exwm-workspace--client-p))
              ;; The following conditions filter out events relating to temp
              ;; buffers.

exwm-manage.el

@@ -91,6 +91,7 @@ You can still make the X windows floating afterwards."
 (defvar exwm-manage--ping-lock nil
   "Non-nil indicates EXWM is pinging a window.")
 
+(defvar exwm-input--skip-buffer-list-update)
 (defvar exwm-input-prefix-keys)
 (defvar exwm-workspace--current)
 (defvar exwm-workspace--id-struts-alist)
@@ -201,7 +202,8 @@ You can still make the X windows floating afterwards."
         (make-instance 'xcb:ChangeSaveSet
                        :mode xcb:SetMode:Insert
                        :window id))
-    (with-current-buffer (generate-new-buffer "*EXWM*")
+    (with-current-buffer (let ((exwm-input--skip-buffer-list-update t))
+                           (generate-new-buffer "*EXWM*"))
       ;; Keep the oldest X window first.
       (setq exwm--id-buffer-alist
             (nconc exwm--id-buffer-alist `((,id . ,(current-buffer)))))
@@ -284,7 +286,8 @@ You can still make the X windows floating afterwards."
                              :stack-mode xcb:StackMode:Below)))
         (xcb:flush exwm--connection)
         (setq exwm--id-buffer-alist (assq-delete-all id exwm--id-buffer-alist))
-        (let ((kill-buffer-query-functions nil))
+        (let ((kill-buffer-query-functions nil)
+              (exwm-input--skip-buffer-list-update t))
           (kill-buffer (current-buffer)))
         (throw 'return 'ignored))
       (let ((index (plist-get exwm--configurations 'workspace)))