Is there any way to have EMACS save your undo history between sessions?
I'm aware of the savehist lib, the saveplace lib, the desktop lib, and the windows lib, these all provide some session control but none seem to save the undo history.
From version 0.4 onwards, undo-tree supports persistent storage of undo-tree data between sessions "out of the box". (Note that there are significant bug-fixes related to this feature in more recent versions; the latest version at the time of writing is 0.6.3.)
Simply enable the undo-tree-auto-save-history customization option to automatically save and load undo history in undo-tree buffers. Or use the undo-tree-save/load-history commands to save and load undo history manually.
You need at least Emacs version 24.3 for this to work reliably, but with a recent enough Emacs it works very well.
Add the following to your .emacs file :
(global-undo-tree-mode)
(setq undo-tree-auto-save-history t)
(setq undo-tree-history-directory-alist '(("." . "~/.emacs.d/undo")))
Explanation
(global-undo-tree-mode) enables undo tree.
(setq undo-tree-auto-save-history t) enables auto save of undo history.
(setq undo-tree-history-directory-alist '(("." . "~/.emacs.d/undo"))) so that your project does not get littered with undo-history savefiles.
Here's some code I wrote which seems to do the trick. It isn't bullet-proof, as in, it doesn't handle all the file handling intricacies that Emacs does (e.g. overriding where auto-save files are put, symlink handling, etc.). But, it seemed to do the trick for some simple text files I manipulated.
(defun save-undo-filename (orig-name)
"given a filename return the file name in which to save the undo list"
(concat (file-name-directory orig-name)
"."
(file-name-nondirectory orig-name)
".undo"))
(defun save-undo-list ()
"Save the undo list to a file"
(save-excursion
(ignore-errors
(let ((undo-to-save `(setq buffer-undo-list ',buffer-undo-list))
(undo-file-name (save-undo-filename (buffer-file-name))))
(find-file undo-file-name)
(erase-buffer)
(let (print-level
print-length)
(print undo-to-save (current-buffer)))
(let ((write-file-hooks (remove 'save-undo-list write-file-hooks)))
(save-buffer))
(kill-buffer))))
nil)
(defvar handling-undo-saving nil)
(defun load-undo-list ()
"load the undo list if appropriate"
(ignore-errors
(when (and
(not handling-undo-saving)
(null buffer-undo-list)
(file-exists-p (save-undo-filename (buffer-file-name))))
(let* ((handling-undo-saving t)
(undo-buffer-to-eval (find-file-noselect (save-undo-filename (buffer-file-name)))))
(eval (read undo-buffer-to-eval))))))
(add-hook 'write-file-hooks 'save-undo-list)
(add-hook 'find-file-hook 'load-undo-list)
desktop-save-mode does not save buffer-undo-list by default. You just have to tell him!
(add-to-list 'desktop-locals-to-save 'buffer-undo-list)
Emacs Session appears to support this:
(add-to-list 'session-locals-include 'buffer-undo-list)
I have managed to get the undo history working by using the information provided here: http://emacs.stackexchange.com/q/3725/2287
Instead of patching the original file desktop.el.gz I created an advice that temporarily overrides (buffer-local-variables) then I use it together with the function that gathers information about the buffer.
(defun +append-buffer-undo-list-to-buffer-local-variables-advice (orig-fn &rest args)
"Override `buffer-local-variables' and call ORIG-FN with ARGS.
There is a bug in Emacs where the `buffer-undo-list' data is
missing from the output of `buffer-local-variables'. This
advice temporarily overrides the function and appends the
missing data."
(let ((orig-buffer-local-variables-fn (symbol-function 'buffer-local-variables)))
(cl-letf (((symbol-function 'buffer-local-variables)
#'(lambda () (append (funcall orig-buffer-local-variables-fn)
`(,(cons 'buffer-undo-list buffer-undo-list))))))
(apply orig-fn args))))
(advice-add #'desktop-buffer-info :around #'+append-buffer-undo-list-to-buffer-local-variables-advice)
(push 'buffer-undo-list desktop-locals-to-save)
(desktop-save-mode 1)
I hope this helps someone else.
Related
I have various things set up in my 'before-save-hook. For example, I run 'delete-trailing-whitespace. This is what I want in almost all occasions.
But sometimes, I'm working on files that are shared with other people, and the file already has a bunch of trailing whitespace. If I save the file, I'll get a big diff that's pretty confusing, as my change is buried in dozens or hundreds of meaningless changes. Yes, everyone could just tell their diff tool to not show whitespace changes, but that's something that everyone has to do every time they look at the diff. I'd rather not even have the whitespace change.
Is there anything I can do to save the file without the whitespace changes, short of starting a new instance of Emacs with no init.el file, or with a modified init.el that doesn't have the hook?
Here is how I save without triggering delete-trailing-whitespace:
C-x C-q C-x C-s C-x C-q: read-only, save, revert read-only
A simpler solution I came up with is that my fundamental-mode has no hooks installed, because I want it to be as plain as possible. Thus if I want to save a file without running hooks, I temporarily switch to fundamental-mode.
Based on a comment discussion with #Stefan, here are two possible (untested) solutions:
Use let:
(defun save-buffer-without-dtw ()
(interactive)
(let ((b (current-buffer))) ; memorize the buffer
(with-temp-buffer ; new temp buffer to bind the global value of before-save-hook
(let ((before-save-hook (remove 'delete-trailing-whitespace before-save-hook)))
(with-current-buffer b ; go back to the current buffer, before-save-hook is now buffer-local
(let ((before-save-hook (remove 'delete-trailing-whitespace before-save-hook)))
(save-buffer)))))))
Use unwind-protect:
(defun save-buffer-without-dtw ()
(interactive)
(let ((restore-global
(memq 'delete-trailing-whitespace (default-value before-save-hook)))
(restore-local
(and (local-variable-p 'before-save-hook)
(memq 'delete-trailing-whitespace before-save-hook))))
(unwind-protect
(progn
(when restore-global
(remove-hook 'before-save-hook 'delete-trailing-whitespace))
(when restore-local
(remove-hook 'before-save-hook 'delete-trailing-whitespace t))
(save-buffer))
(when restore-global
(add-hook 'before-save-hook 'delete-trailing-whitespace))
(when restore-local
(add-hook 'before-save-hook 'delete-trailing-whitespace nil t)))))
The problem with the second solution is that the order of functions in the before-save-hook may change.
Here's another solution:
(defvar my-inhibit-dtw nil)
(defun my-delete-trailing-whitespace ()
(unless my-inhibit-dtw (delete-trailing-whitespace)))
(add-hook 'before-save-hook 'my-delete-trailing-whitespace)
and then
(defun my-inhibit-dtw ()
(interactive)
(set (make-local-variable 'my-inhibit-dtw) t))
so you can M-x my-inhibit-dtw RET in the buffers where you don't want to trim whitespace.
I wrote a command inspired by Nicholas Douma's solution.
(defun olav-save-buffer-as-is ()
"Save file \"as is\", that is in read-only-mode."
(interactive)
(if buffer-read-only
(save-buffer)
(read-only-mode 1)
(save-buffer)
(read-only-mode 0)))
What we need to do is remove 'delete-trailing-whitespace from before-save-hook, save the buffer, then add it back.
This code will do that, but only remove and add it if it's there to begin with.
;; save the buffer, removing and readding the 'delete-trailing-whitespace function
;; to 'before-save-hook if it's there
(defun save-buffer-no-delete-trailing-whitespace ()
(interactive)
(let ((normally-should-delete-trailing-whitespace (memq 'delete-trailing-whitespace before-save-hook)))
(when normally-should-delete-trailing-whitespace
(remove-hook 'before-save-hook 'delete-trailing-whitespace))
(save-buffer)
(when normally-should-delete-trailing-whitespace
(add-hook 'before-save-hook 'delete-trailing-whitespace))))
(global-set-key (kbd "C-c C-s") 'save-buffer-no-delete-trailing-whitespace)
It also binds the command to (kbd C-c C-s), for convenience.
Is there any way to have EMACS save your undo history between sessions?
I'm aware of the savehist lib, the saveplace lib, the desktop lib, and the windows lib, these all provide some session control but none seem to save the undo history.
From version 0.4 onwards, undo-tree supports persistent storage of undo-tree data between sessions "out of the box". (Note that there are significant bug-fixes related to this feature in more recent versions; the latest version at the time of writing is 0.6.3.)
Simply enable the undo-tree-auto-save-history customization option to automatically save and load undo history in undo-tree buffers. Or use the undo-tree-save/load-history commands to save and load undo history manually.
You need at least Emacs version 24.3 for this to work reliably, but with a recent enough Emacs it works very well.
Add the following to your .emacs file :
(global-undo-tree-mode)
(setq undo-tree-auto-save-history t)
(setq undo-tree-history-directory-alist '(("." . "~/.emacs.d/undo")))
Explanation
(global-undo-tree-mode) enables undo tree.
(setq undo-tree-auto-save-history t) enables auto save of undo history.
(setq undo-tree-history-directory-alist '(("." . "~/.emacs.d/undo"))) so that your project does not get littered with undo-history savefiles.
Here's some code I wrote which seems to do the trick. It isn't bullet-proof, as in, it doesn't handle all the file handling intricacies that Emacs does (e.g. overriding where auto-save files are put, symlink handling, etc.). But, it seemed to do the trick for some simple text files I manipulated.
(defun save-undo-filename (orig-name)
"given a filename return the file name in which to save the undo list"
(concat (file-name-directory orig-name)
"."
(file-name-nondirectory orig-name)
".undo"))
(defun save-undo-list ()
"Save the undo list to a file"
(save-excursion
(ignore-errors
(let ((undo-to-save `(setq buffer-undo-list ',buffer-undo-list))
(undo-file-name (save-undo-filename (buffer-file-name))))
(find-file undo-file-name)
(erase-buffer)
(let (print-level
print-length)
(print undo-to-save (current-buffer)))
(let ((write-file-hooks (remove 'save-undo-list write-file-hooks)))
(save-buffer))
(kill-buffer))))
nil)
(defvar handling-undo-saving nil)
(defun load-undo-list ()
"load the undo list if appropriate"
(ignore-errors
(when (and
(not handling-undo-saving)
(null buffer-undo-list)
(file-exists-p (save-undo-filename (buffer-file-name))))
(let* ((handling-undo-saving t)
(undo-buffer-to-eval (find-file-noselect (save-undo-filename (buffer-file-name)))))
(eval (read undo-buffer-to-eval))))))
(add-hook 'write-file-hooks 'save-undo-list)
(add-hook 'find-file-hook 'load-undo-list)
desktop-save-mode does not save buffer-undo-list by default. You just have to tell him!
(add-to-list 'desktop-locals-to-save 'buffer-undo-list)
Emacs Session appears to support this:
(add-to-list 'session-locals-include 'buffer-undo-list)
I have managed to get the undo history working by using the information provided here: http://emacs.stackexchange.com/q/3725/2287
Instead of patching the original file desktop.el.gz I created an advice that temporarily overrides (buffer-local-variables) then I use it together with the function that gathers information about the buffer.
(defun +append-buffer-undo-list-to-buffer-local-variables-advice (orig-fn &rest args)
"Override `buffer-local-variables' and call ORIG-FN with ARGS.
There is a bug in Emacs where the `buffer-undo-list' data is
missing from the output of `buffer-local-variables'. This
advice temporarily overrides the function and appends the
missing data."
(let ((orig-buffer-local-variables-fn (symbol-function 'buffer-local-variables)))
(cl-letf (((symbol-function 'buffer-local-variables)
#'(lambda () (append (funcall orig-buffer-local-variables-fn)
`(,(cons 'buffer-undo-list buffer-undo-list))))))
(apply orig-fn args))))
(advice-add #'desktop-buffer-info :around #'+append-buffer-undo-list-to-buffer-local-variables-advice)
(push 'buffer-undo-list desktop-locals-to-save)
(desktop-save-mode 1)
I hope this helps someone else.
I am involved in python project where tabs are used, however i am not using them in every other code i write, it is vital to use them in that particular project. Projects are located in one directory under specific directories. I.E:
\main_folder
\project1
\project2
\project3
...etc
I have couple functions/hooks on file open and save that untabify and tabify whole buffer i work on.
;; My Functions
(defun untabify-buffer ()
"Untabify current buffer"
(interactive)
(untabify (point-min) (point-max)))
(defun tabify-buffer ()
"Tabify current buffer"
(interactive)
(tabify (point-min) (point-max)))
;; HOOKS
; untabify buffer on open
(add-hook 'find-file-hook 'untabify-buffer)
; tabify on save
(add-hook 'before-save-hook 'tabify-buffer)
If i put it in .emacs file it is run on every .py file i open which is not what i want. What i`d like to have is to have these hooks used only in one particular folder with respective subfolders. Tried .dir_locals but it works only for properties not hooks. I can not use hooks in specific modes (i.e. python-mode) as almost all projects are written in python. To be honest i tried writing elisp conditional save but failed.
A very easy solution is to just add a configuration variable that can be used to disable the hooks. For example:
(defvar tweak-tabs t)
(add-hook 'find-file-hook
(lambda () (when tweak-tabs (untabify (point-min) (point-max)))))
(add-hook 'before-save-hook
(lambda () (when tweak-tabs (tabify (point-min) (point-max)))))
Now you can add a .dir-locals.el file in the relevant directories, setting tweak-tabs to nil, disabling this feature there.
(But another problem is that this is a pretty bad way to deal with tabs. For example, after you save a file you do see the tabs in it.)
Just for the record, to answer the literal question in the title (as I reached this question via a web search): one way to add a hook that depends on file location is to make it a function that checks for buffer-file-name. (Idea from this answer.)
For example, for the exact same problem (turn on tabs only in a particular directory, and leave tabs turned off elsewhere), I'm currently doing something like (after having installed the package smart-tabs-mode with M-x package-install):
(smart-tabs-insinuate 'python) ; This screws up all Python files (inserts tabs)
(add-hook 'python-mode-hook ; So we need to un-screw most of them
(lambda ()
(unless (and (stringp buffer-file-name)
(string-match "specialproject" buffer-file-name))
(setq smart-tabs-mode nil)))
t) ; Add this hook to end of the list
(This is a bit inverted, as smart-tabs-insinuate itself modifies python-mode-hook and then we're modifying it back, but it should do as an example.)
I am finding myself editing a lot of files that are read-only. I usually hit C-x C-q to call toggle-read-only. Then I hit C-x C-s to save and get,
File foo.txt is write-protected; try to save anyway? (y or n)
After hitting y, the file is saved and the permissions on the file remain read-only.
Is there a way to shorten this process and make it so that simply saving a file with C-x C-s does the whole thing without prompting? Should I look into inserting chmod in before-save-hook and after-save-hook or is there a better way?
Adding a call to chmod in before-save-hook would be clean way to accomplish this. There isn't any setting you can change to avoid the permissions check.
Based on the follow-up question, it sounds like you'd like the files to be changed to writable by you automatically upon opening. This code does the trick:
(defun change-file-permissions-to-writable ()
"to be run from find-file-hook, change write permissions"
(when (not (file-writable-p buffer-file-name))
(chmod buffer-file-name (file-modes-symbolic-to-number "u+w" (nth 8 (file-attributes buffer-file-name))))
(if (not (file-writable-p buffer-file-name))
(message "Unable to make file writable."))))
(add-hook 'find-file-hook 'change-file-permissions-to-writable)
Note: When I tested it on my Windows machine, the file permissions didn't show up until I tried to save the buffer, but it worked as expected. I personally feel uneasy about this customization, but it's your Emacs. :)
I agree with Trey that universally doing a chmod on write is risky -- read-only files are read-only for a reason, IMHO. Here's a way to specifically override things on a per-buffer basis. It's not ideal in that it overrides file-writable-p for the life of the buffer (or at least until you toggle my-override-mode-on-save back to nil), but it makes you make a conscious decision on a file-by-file basis (sort-of; it's really a buffer-by-buffer basis, which is fairly similar). Of course since you're looking to automatically toggle the read-only flag when the file is visited, you might not be interested in this distinction. Still, here it is; enjoy it or ignore it as you will.
(make-variable-buffer-local
(defvar my-override-mode-on-save nil
"Can be set to automatically ignore read-only mode of a file when saving."))
(defadvice file-writable-p (around my-overide-file-writeable-p act)
"override file-writable-p if `my-override-mode-on-save' is set."
(setq ad-return-value (or
my-override-mode-on-save
ad-do-it)))
(defun my-override-toggle-read-only ()
"Toggle buffer's read-only status, keeping `my-override-mode-on-save' in sync."
(interactive)
(setq my-override-mode-on-save (not my-override-mode-on-save))
(toggle-read-only))
P.S. Thanks to Trey for the ad-return-value pointer in the other SO question.
Since I find it useful to be constantly reminded that I am about to edit a file I do not have permissions to, when I open a file in a buffer I want to force myself to proactively make the buffer writable wit C-x q. Opening it with tramp by hand however is quite tedious so I advise save-buffer to prompt me for password if it fails to write. I totally recommend you put this snippet in your .emacs
(defadvice save-buffer (around save-buffer-as-root-around activate)
"Use sudo to save the current buffer."
(interactive "p")
(if (and (buffer-file-name) (not (file-writable-p (buffer-file-name))))
(let ((buffer-file-name (format "/sudo::%s" buffer-file-name)))
ad-do-it)
ad-do-it))
For a reason I could no determine the Trey Jackson solution does not work on my gnu emacs 25.2 under windows: the file-modes-rights-to-number called from file-modes-rights-to-number fails.
If someone is stuck with the same problem he could use a less elegant but working solution replace block :
(chmod buffer-file-name (file-modes-symbolic-to-number "u+w" (nth 8 (file-attributes buffer-file-name))))
with block :
(cond ((or (eq system-type 'ms-dos) (eq system-type 'windows-nt))
(progn
(shell-command-to-string (concat "attrib -R " (buffer-file-name (current-buffer))))
(message "Setting file and buffer to writeable (%s style)" system-type)
))
((eq system-type 'gnu/linux)
(progn
(shell-command-to-string (concat "chmod u+w " (buffer-file-name (current-buffer))))
(message "Setting file and buffer to writeable (%s style)" system-type)
))
(t (message "file permission change not handle for OS %s" system-type))
)
There are plenty of ways to fold code in Emacs and I've settled in on using the outline minor mode... it works great!
However, I really want my folding to be persisted when I close and re-open files. It is quite frustrating to have folding set up in a file the way I like it, only to have that lost when I restart Emacs.
Has anyone found a way to keep the folding state of a file persistent?
Edit: Now that I understand the question...
How about something like the following nippet of code. It seems to work for me, though I haven't figured out how to avoid being prompted for the file local variable every time.
(defvar omm-state nil
"file local variable storing outline overlays")
(defun omm-state-mode (&optional arg)
"poor man's minor mode to re-apply the outline overlays "
(interactive)
(omm-re-enable-outline-state)
(add-hook 'before-save-hook 'omm-state-save))
(defun omm-get-all-overlays ()
"return a list of outline information for all the current buffer"
(save-excursion
(let ((all-overlays (overlays-in (point-min) (point-max))))
(mapcar (lambda (o)
(list (overlay-start o) (overlay-end o) (overlay-get o 'invisible)))
(reverse all-overlays)))))
(defun omm-re-enable-outline-state (&optional arg)
"turn on outline-minor-mode and re-apply the outline information"
(outline-minor-mode 1)
(when (listp omm-state)
(mapcar (lambda (p)
(apply 'outline-flag-region p))
omm-state)))
(defun omm-state-save ()
"save the outline state in a file local variable
Note: this just replaces the existing value, you need to start
it off by adding something like this to your file:
# Local Variables:
# omm-state:()
# mode:omm-state
# End:
"
(ignore-errors
(save-excursion
(goto-char (point-max))
(when (search-backward "omm-state:" nil t)
(goto-char (match-end 0))
(kill-sexp)
(princ (omm-get-all-overlays) (current-buffer)))))
nil)
This solution requires you "seeding" your file with something like:
# Local Variables:
# omm-state:()
# mode:omm-state
# End:
I realize this is an old post but FWIW I created a minor mode that complements hs-minor-mode, outline-mode etc. I also "really want my folding to be persisted when I close and re-open files". :)
The package is in MELPA as of today and called persistent-overlays.
It is also available directly on github: https://github.com/mneilly/Emacs-Persistent-Overlays