Use frame's buffer-predicate instead of doom/{next,previous}-buffer

doom/{next,previous}-buffer was implemented so that these commands could
skip over unreal buffers, and land us on either a real one or the
dashboard. Using the frame's buffer-predicate parameter accomplishes
exactly this, natively.

core/autoload/buffers.el

@@ -34,6 +34,13 @@ it if it doesn't exist).")
 ;; Functions
 ;;
 
+;;;###autoload
+(defun doom-buffer-frame-predicate (buf)
+  "To be used as the default frame buffer-predicate parameter. Returns nil if
+BUF should be skipped over by functions like `next-buffer' and `other-buffer'."
+  (or (doom-real-buffer-p buf)
+      (eq buf (doom-fallback-buffer))))
+
 ;;;###autoload
 (defun doom-fallback-buffer ()
   "Returns the fallback buffer, creating it if necessary. By default this is the
@@ -279,17 +286,3 @@ processes killed."
           (delete-process p)
           (cl-incf n))))
     n))
-
-;;;###autoload
-(defun doom/next-buffer ()
-  "Switch to the next real buffer, skipping non-real buffers. See
-`doom-real-buffer-p' for what 'real' means."
-  (interactive)
-  (doom--cycle-real-buffers +1))
-
-;;;###autoload
-(defun doom/previous-buffer ()
-  "Switch to the previous real buffer, skipping non-real buffers. See
-`doom-real-buffer-p' for what 'real' means."
-  (interactive)
-  (doom--cycle-real-buffers -1))

core/core-ui.el

@@ -481,6 +481,8 @@ character that looks like a space that `whitespace-mode' won't affect.")
 (global-eldoc-mode -1)
 ;; simple name in frame title
 (setq-default frame-title-format '("DOOM Emacs"))
+;; make `next-buffer', `other-buffer', etc. ignore unreal buffers
+(push '(buffer-predicate . doom-buffer-frame-predicate) default-frame-alist)
 ;; draw me like one of your French editors
 (tooltip-mode -1) ; relegate tooltips to echo area only
 (menu-bar-mode -1)
@@ -538,9 +540,8 @@ instead)."
   (let ((buf (current-buffer)))
     (cond ((window-dedicated-p)
            (delete-window))
-          ((eq buf (doom-fallback-buffer))
-           (doom--cycle-real-buffers -1))
           ((doom-real-buffer-p buf)
+           (previous-buffer)
            (doom--cycle-real-buffers
             (if (delq buf (doom-real-buffer-list)) -1))
            (kill-buffer buf))