make `previous-buffer` and `next-buffer` to ignore some buffers

Question

in Helm I ignore some buffers from showing when using C-x b, I'm looking for a way to make the commands previous-buffer and next-buffer behave the same ignoring some buffers.

Answer 1

Here are two ways:

1. If you take a look at the definition of function switch-to-next-buffer (in library window.el) you will see that it filters the buffers by the predicate (if any) that is the value of frame parameter buffer-predicate. That function is used by next-buffer.

   You can set that frame parameter to a predicate that filters the way you want.

2. You can simply advise function switch-to-next-buffer to filter the way you want. You will essentially replace its definition by almost the same definition, but filter additionally the way you want.

Similarly for switch-to-previous-buffer.

Answer 2

(defcustom my-skippable-buffers '("*Messages*" "*scratch*" "*Help*")
  "Buffer names ignored by `my-next-buffer' and `my-previous-buffer'."
  :type '(repeat string))

(defun my-change-buffer (change-buffer)
  "Call CHANGE-BUFFER until current buffer is not in `my-skippable-buffers'."
  (let ((initial (current-buffer)))
    (funcall change-buffer)
    (let ((first-change (current-buffer)))
      (catch 'loop
        (while (member (buffer-name) my-skippable-buffers)
          (funcall change-buffer)
          (when (eq (current-buffer) first-change)
            (switch-to-buffer initial)
            (throw 'loop t)))))))

(defun my-next-buffer ()
  "Variant of `next-buffer' that skips `my-skippable-buffers'."
  (interactive)
  (my-change-buffer 'next-buffer))

(defun my-previous-buffer ()
  "Variant of `previous-buffer' that skips `my-skippable-buffers'."
  (interactive)
  (my-change-buffer 'previous-buffer))

(global-set-key [remap next-buffer] 'my-next-buffer)
(global-set-key [remap previous-buffer] 'my-previous-buffer)

Or if you wanted to ignore buffer names matching a pattern, you could use this variant.

(defcustom my-skippable-buffer-regexp
  (rx bos (or "*Messages*" "*scratch*" "*Help*") eos)
  "Matching buffer names are ignored by `my-next-buffer'
and `my-previous-buffer'."
  :type 'regexp)

(defun my-change-buffer (change-buffer)
  "Call CHANGE-BUFFER until `my-skippable-buffer-regexp' doesn't match."
  (let ((initial (current-buffer)))
    (funcall change-buffer)
    (let ((first-change (current-buffer)))
      (catch 'loop
        (while (string-match-p my-skippable-buffer-regexp (buffer-name))
          (funcall change-buffer)
          (when (eq (current-buffer) first-change)
            (switch-to-buffer initial)
            (throw 'loop t)))))))

(defun my-next-buffer ()
  "Variant of `next-buffer' that skips `my-skippable-buffer-regexp'."
  (interactive)
  (my-change-buffer 'next-buffer))

(defun my-previous-buffer ()
  "Variant of `previous-buffer' that skips `my-skippable-buffer-regexp'."
  (interactive)
  (my-change-buffer 'previous-buffer))

(global-set-key [remap next-buffer] 'my-next-buffer)
(global-set-key [remap previous-buffer] 'my-previous-buffer)

For the example from the comments, to tell this latter version to also skip all buffer names beginning with helm, we could use:

(setq my-skippable-buffer-regexp
      (rx bos (or (or "*Messages*" "*scratch*" "*Help*")
                  (seq "helm" (zero-or-more anything)))
          eos))