Re: Partial wdired (edit just filename at the point)

[Arthur Miller <arthur.miller@live.com>]

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Arthur Miller <arthur.miller@live.com> writes:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>>> The problem here is how aborting changes is implemented in wdired: undo
>>> is disabled and original code just copies entire buffer and pastes it back
>>> when changes are aborted.
>>
>> I think you should be able to leave this part of the code completely unchanged.
>
> Yes; and for the simplicity it will be so.
>
>>> I would like to skip copying entire buffer into buffer-string as
>>> wdired does originally.
>>
>> Any particular reason for that?  It should be very fast, even for very
>> large directories.
>
> Just for efficiency; it copies entire buffer which can be quite big
> memory wise; but indeed it seems to be very fast, and I guess for the
> simplicity of implementation it can be left as is :-).
>
>>> I agree with you, but I am not sure how to implement it. My hack was
>>> literally less than a 5 minute change, I just removed loops and changed
>>> mode name so I can abort it properly.
>>
>> I'd start with the following:
>> When converting to wdired, instead of calling `wdired-preprocess-files`, use
>>
>>     (add-hook 'before-change-functions #'wdired--preprocess-lines nil t)
>>
>> and then turn `wdired-preprocess-files` into `wdired--preprocess-lines`,
>> which will `get-text-property` of the first char of each line in the
>> region to see if it's already been marked as `read-only`.  If yes,
>> do nothing and if not, do what the old code did on that line.
>
> I tested, and currently I don't see any noticable slowdowns, even on
> that large directory. Dropping into wdired seems to be quite reactive
> and I can start editing any file name immidiately.
>
> However I can't seem to be able to get it work with permissions; I am
> not sure why. I have checked that wdired-allow-to-change-permissions is t.
>
> I have attached code as a separate file (I worked so). I can make a
> patch for wdired.el later, if you or someone can give me a tip why text
> props for permissions are not changing as they should.

I change my mind :-) I have tested with emacs -Q option, and I see same
behaviour with permission properties with original wdired code, so I
guess it works properly (or as buggy as original). Someone please test
it though.

Attached is a patch for wdired based on current master.


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From cddace1dae6cb9e4367f1fad3d7bd3745282824d Mon Sep 17 00:00:00 2001
From: Arthur Miller <arthur.miller@live.com>
Date: Wed, 17 Mar 2021 23:24:10 +0100
Subject: [PATCH] Make wdired lazy

---
 lisp/wdired.el | 156 +++++++++++++++++++++++--------------------------
 1 file changed, 74 insertions(+), 82 deletions(-)

diff --git a/lisp/wdired.el b/lisp/wdired.el
index c495d8de34..ba71306e66 100644
--- a/lisp/wdired.el
+++ b/lisp/wdired.el
@@ -250,20 +250,11 @@ wdired-change-to-wdired-mode
   (setq buffer-read-only nil)
   (dired-unadvertise default-directory)
   (add-hook 'kill-buffer-hook 'wdired-check-kill-buffer nil t)
+  (add-hook 'before-change-functions 'wdired--preprocess-line nil t)
   (add-hook 'after-change-functions 'wdired--restore-properties nil t)
   (setq major-mode 'wdired-mode)
   (setq mode-name "Editable Dired")
   (setq revert-buffer-function 'wdired-revert)
-  ;; I temp disable undo for performance: since I'm going to clear the
-  ;; undo list, it can save more than a 9% of time with big
-  ;; directories because setting properties modify the undo-list.
-  (buffer-disable-undo)
-  (wdired-preprocess-files)
-  (if wdired-allow-to-change-permissions
-      (wdired-preprocess-perms))
-  (if (fboundp 'make-symbolic-link)
-      (wdired-preprocess-symlinks))
-  (buffer-enable-undo) ; Performance hack. See above.
   (set-buffer-modified-p nil)
   (setq buffer-undo-list nil)
   (run-mode-hooks 'wdired-mode-hook)
@@ -278,25 +269,33 @@ wdired-isearch-filter-read-only
 
 ;; Protect the buffer so only the filenames can be changed, and put
 ;; properties so filenames (old and new) can be easily found.
-(defun wdired-preprocess-files ()
-  (put-text-property (point-min) (1+ (point-min))'front-sticky t)
-  (save-excursion
-    (goto-char (point-min))
-    (let ((b-protection (point))
-          (used-F (dired-check-switches dired-actual-switches "F" "classify"))
-	  filename)
-      (while (not (eobp))
-	(setq filename (dired-get-filename nil t))
-        (when (and filename
-		   (not (member (file-name-nondirectory filename) '("." ".."))))
-	  (dired-move-to-filename)
-	  ;; The rear-nonsticky property below shall ensure that text preceding
-	  ;; the filename can't be modified.
-	  (add-text-properties
-	   (1- (point)) (point) `(old-name ,filename rear-nonsticky (read-only)))
-	  (put-text-property b-protection (point) 'read-only t)
-          (dired-move-to-end-of-filename t)
-	  (put-text-property (point) (1+ (point)) 'end-name t))
+(defun wdired--preprocess-line (beg end)
+  "Preprocess current line under point to make it writable.  "
+  (let ((inhibit-read-only t))
+    (unless (get-text-property (line-beginning-position) 'front-sticky)
+      (buffer-disable-undo)
+      (put-text-property (line-beginning-position) (1+
+                                                    (line-beginning-position))
+                         'front-sticky t)
+      (save-excursion
+        (goto-char (line-beginning-position))
+        (let ((b-protection (point))
+              (used-F (dired-check-switches
+                       dired-actual-switches "F" "classify"))
+	      filename)
+          (setq filename (dired-get-filename nil t))
+          (when (and filename
+		     (not (member (file-name-nondirectory filename) '("."
+                                                                      ".."))))
+	    (dired-move-to-filename)
+	    ;; The rear-nonsticky property below shall ensure that text
+            ;; preceding the filename can't be modified.
+	    (add-text-properties
+	     (1- (point)) (point)
+             `(old-name ,filename rear-nonsticky (read-only)))
+	    (put-text-property b-protection (point) 'read-only t)
+            (dired-move-to-end-of-filename t)
+	    (put-text-property (point) (1+ (point)) 'end-name t))
           (when (and used-F (looking-at "[*/@|=>]$")) (forward-char))
           (when (save-excursion
                   (and (re-search-backward
@@ -304,9 +303,51 @@ wdired-preprocess-files
                        (looking-at "l")
                        (search-forward " -> " (line-end-position) t)))
             (goto-char (line-end-position)))
-	  (setq b-protection (point))
-        (forward-line))
-      (put-text-property b-protection (point-max) 'read-only t))))
+          (setq b-protection (point))
+          (put-text-property b-protection (line-end-position)
+                             'read-only t))
+
+        ;; Put a keymap property to the permission bits of the files,
+        ;; and store the original name and permissions as a property
+        (when wdired-allow-to-change-permissions
+          (goto-char (line-beginning-position))
+          (setq-local wdired-col-perm nil)
+          (when (and (not (looking-at dired-re-sym))
+		     (wdired-get-filename)
+		     (re-search-forward dired-re-perms
+                                        (line-end-position) 'eol))
+	    (let ((begin (match-beginning 0))
+	          (end (match-end 0)))
+	      (unless wdired-col-perm
+	        (setq wdired-col-perm (- (current-column) 9)))
+	      (if (eq wdired-allow-to-change-permissions 'advanced)
+	          (progn
+		    (put-text-property begin end 'read-only nil)
+		    ;; make first permission bit writable
+		    (put-text-property
+		     (1- begin) begin 'rear-nonsticky '(read-only)))
+	        ;; avoid that keymap applies to text following permissions
+	        (add-text-properties
+	         (1+ begin) end
+	         `(keymap ,wdired-perm-mode-map rear-nonsticky (keymap))))
+	      (put-text-property end (1+ end) 'end-perm t)
+	      (put-text-property
+	       begin (1+ begin) 'old-perm (match-string-no-properties 0)))))
+
+        ;; Put the needed properties to allow the user to change
+        ;; links' targets
+        (when (fboundp 'make-symbolic-link)
+          (goto-char (line-beginning-position))
+          (when (looking-at dired-re-sym)
+            (re-search-forward " -> \\(.*\\)$")
+	    (put-text-property (1- (match-beginning 1))
+			       (match-beginning 1) 'old-link
+			       (match-string-no-properties 1))
+            (put-text-property (match-end 1) (1+ (match-end 1)) 'end-link t)
+            (unless wdired-allow-to-redirect-links
+              (put-text-property (match-beginning 0)
+			         (match-end 1) 'read-only t))))))
+    (buffer-enable-undo)))
 
 ;; This code is a copy of some dired-get-filename lines.
 (defsubst wdired-normalize-filename (file unquotep)
@@ -369,7 +410,6 @@ wdired-get-filename
 	(and file (> (length file) 0)
              (concat (dired-current-directory) file))))))
 
-
 (defun wdired-change-to-dired-mode ()
   "Change the mode back to dired."
   (or (eq major-mode 'wdired-mode)
@@ -390,10 +430,10 @@ wdired-change-to-dired-mode
   (remove-hook 'after-change-functions 'wdired--restore-properties t)
   (setq-local revert-buffer-function 'dired-revert))
 
-
 (defun wdired-abort-changes ()
   "Abort changes and return to dired mode."
   (interactive)
+  (remove-hook 'before-change-functions 'wdired--preprocess-line t)
   (let ((inhibit-read-only t))
     (erase-buffer)
     (insert wdired-old-content)
@@ -709,23 +749,6 @@ wdired-previous-line
 				  (current-column)))))
       (dired-move-to-filename)))
 
-;; Put the needed properties to allow the user to change links' targets
-(defun wdired-preprocess-symlinks ()
-  (let ((inhibit-read-only t))
-    (save-excursion
-      (goto-char (point-min))
-      (while (not (eobp))
-        (when (looking-at dired-re-sym)
-          (re-search-forward " -> \\(.*\\)$")
-	  (put-text-property (1- (match-beginning 1))
-			     (match-beginning 1) 'old-link
-			     (match-string-no-properties 1))
-          (put-text-property (match-end 1) (1+ (match-end 1)) 'end-link t)
-          (unless wdired-allow-to-redirect-links
-            (put-text-property (match-beginning 0)
-			       (match-end 1) 'read-only t)))
-        (forward-line)))))
-
 (defun wdired-get-previous-link (&optional old move)
   "Return the next symlink target.
 If OLD, return the old target.  If MOVE, move point before it."
@@ -828,37 +851,6 @@ wdired-perm-mode-map
     (define-key map [down-mouse-1] 'wdired-mouse-toggle-bit)
     map))
 
-;; Put a keymap property to the permission bits of the files, and store the
-;; original name and permissions as a property
-(defun wdired-preprocess-perms ()
-  (let ((inhibit-read-only t))
-    (setq-local wdired-col-perm nil)
-    (save-excursion
-      (goto-char (point-min))
-      (while (not (eobp))
-	(when (and (not (looking-at dired-re-sym))
-		   (wdired-get-filename)
-		   (re-search-forward dired-re-perms (line-end-position) 'eol))
-	  (let ((begin (match-beginning 0))
-		(end (match-end 0)))
-	    (unless wdired-col-perm
-	      (setq wdired-col-perm (- (current-column) 9)))
-	    (if (eq wdired-allow-to-change-permissions 'advanced)
-		(progn
-		  (put-text-property begin end 'read-only nil)
-		  ;; make first permission bit writable
-		  (put-text-property
-		   (1- begin) begin 'rear-nonsticky '(read-only)))
-	      ;; avoid that keymap applies to text following permissions
-	      (add-text-properties
-	       (1+ begin) end
-	       `(keymap ,wdired-perm-mode-map rear-nonsticky (keymap))))
-	    (put-text-property end (1+ end) 'end-perm t)
-	    (put-text-property
-	     begin (1+ begin) 'old-perm (match-string-no-properties 0))))
-        (forward-line)
-	(beginning-of-line)))))
-
 (defun wdired-perm-allowed-in-pos (char pos)
   (cond
    ((= char ?-)          t)
-- 
2.31.0