From 99a82ac8f0bbc149e6df738c8d41d4ebfe17775c Mon Sep 17 00:00:00 2001
From: Sean Whitton <spwhitton@spwhitton.name>
Date: Sat, 21 May 2022 18:32:29 -0700
Subject: restore commands for switching to a buffer with a given major mode

---
 .emacs.d/init.el | 84 ++++++++++++++++++++++++++------------------------------
 1 file changed, 39 insertions(+), 45 deletions(-)

diff --git a/.emacs.d/init.el b/.emacs.d/init.el
index 3123dc91..505e06d4 100644
--- a/.emacs.d/init.el
+++ b/.emacs.d/init.el
@@ -893,9 +893,11 @@ layout (which I use by default)."
 ;; `display-buffer-fallback-action' is a constant so cons once in advance.
 (let ((ac `(,(car display-buffer-fallback-action) (inhibit-same-window . t))))
   (defun spw/display-buffer (orig-fun &rest args)
-    (if (memq this-command '(display-buffer
-			     project-display-buffer
-			     transient-cycles-cmd-display-buffer))
+    (if (memq this-command
+	      '(display-buffer
+		project-display-buffer
+		transient-cycles-cmd-display-buffer
+		transient-cycles-cmd-spw/display-recent-major-mode-buffer))
 	(let ((display-buffer-overriding-action ac))
 	  (apply orig-fun args))
       (apply orig-fun args))))
@@ -1124,48 +1126,40 @@ don't consider windows satisfying the predicate EXCLUDE."
       (if (> count 0) (tab-bar-history-forward) (tab-bar-history-back))))
   :cycle-backwards-key [left] :cycle-forwards-key [right])
 
-;; For when the buffer's name isn't much help for switching to it, as is often
-;; the case with notmuch buffers.  Commented out for now because the transient
-;; cycling appended to C-x b and C-x 4 C-o now includes buffers of the same
-;; major mode after cloned siblings, so I think I can do without these
-;; additional bindings.
-;; (defun spw/read-major-mode-buffer-ring ()
-;;   (let ((buffer-lists (make-hash-table)))
-;;     (dolist (buffer (buffer-list))
-;;       (with-current-buffer buffer
-;; 	(puthash major-mode
-;; 		 (cons buffer (gethash major-mode buffer-lists))
-;; 		 buffer-lists)))
-;;     (let* ((mode (intern (completing-read "Major mode: "
-;; 					  (hash-table-keys buffer-lists)
-;; 					  nil
-;; 					  t)))
-;; 	   (ring (make-ring (length (gethash mode buffer-lists)))))
-;;       (dolist (buffer (gethash mode buffer-lists) ring)
-;; 	(ring-insert ring buffer)))))
-;; (defun spw/switch-to-major-mode-buffer ()
-;;   (interactive)
-;;   (let ((ring (spw/read-major-mode-buffer-ring)))
-;;     (pop-to-buffer-same-window (ring-ref ring 0))
-;;     ring))
-;; (defun spw/display-major-mode-buffer ()
-;;   (interactive)
-;;   (let ((ring (spw/read-major-mode-buffer-ring)))
-;;     (cons
-;;      (display-buffer (ring-ref ring 0))
-;;      ring)))
-;; (spw/bind-command-with-ret-val-cycling
-;;  ("\C-cb\C-o" . spw/display-major-mode-buffer)
-;;  (spw/buffer-ring-cycle-lambda
-;;   (cdr ret-val)
-;;   (with-selected-window (car ret-val)
-;;     (let ((display-buffer-overriding-action '((display-buffer-same-window)
-;; 					      (inhibit-same-window . nil))))
-;;       (display-buffer buffer)))))
-;; (spw/bind-command-with-ret-val-cycling
-;;  ("\C-cbb" . spw/switch-to-major-mode-buffer)
-;;  (spw/buffer-ring-cycle-lambda
-;;   (and (ring-p ret-val) ret-val)))
+;;; For when the buffer's name isn't much help for switching to it, as is
+;;; often the case with `notmuch-show' buffers.  We select the most recent
+;;; buffer but then transient cycling can take us to other buffers of the same
+;;; major mode.
+
+(defun spw/read-major-mode-recent-buffer ()
+  (let ((buffers (make-hash-table)))
+    (dolist (buffer (buffer-list))
+      (with-current-buffer buffer
+	(unless (gethash major-mode buffers)
+	  (puthash major-mode buffer buffers))))
+    (list
+     (gethash
+      (intern
+       (completing-read
+	"Most recent buffer of major mode: " (hash-table-keys buffers) nil t))
+      buffers))))
+
+(spw/transient-cycles-define-buffer-switch
+  ((("\C-zb" . spw/switch-to-recent-major-mode-buffer) (buffer)
+      (interactive (spw/read-major-mode-recent-buffer))
+      (switch-to-buffer buffer t))
+
+   (("\C-z4b" . spw/switch-to-recent-major-mode-buffer-other-window) (buffer)
+      (interactive (spw/read-major-mode-recent-buffer))
+      (switch-to-buffer-other-window buffer t))
+
+   (("\C-z5b" . spw/switch-to-recent-major-mode-buffer-other-frame) (buffer)
+      (interactive (spw/read-major-mode-recent-buffer))
+      (switch-to-buffer-other-frame buffer t))
+
+   (("\C-z4\C-o" . spw/display-recent-major-mode-buffer) (buffer)
+      (interactive (spw/read-major-mode-recent-buffer))
+      (display-buffer buffer))))
 
 ;; filling of comments -- we don't want to set
 ;; `comment-auto-fill-only-comments' always on because in Org-mode, for
-- 
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