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Re: An idea: combine-change-calls
From: |
Alan Mackenzie |
Subject: |
Re: An idea: combine-change-calls |
Date: |
Mon, 26 Mar 2018 20:17:28 +0000 |
User-agent: |
Mutt/1.7.2 (2016-11-26) |
Hello, Stefan.
On Sun, Mar 25, 2018 at 16:05:40 -0400, Stefan Monnier wrote:
> > I've actually got a working implementation going. It is this:
> > (defmacro combine-change-calls (beg end &rest form)
> > `(if (not inhibit-modification-hooks)
> > (let* ((-beg- ,beg) (-end- ,end)
> > (end-marker (copy-marker -end-)))
> > (run-hook-with-args 'before-change-functions beg end)
> > (let ((inhibit-modification-hooks t))
> > ,@form)
> > (run-hook-with-args 'after-change-functions
> > beg (marker-position end-marker)
> > (- -end- -beg-)))
> > ,@form))
> You need to evaluate `beg` and `end` even if inhibit-modification-hooks
> is set, otherwise someone will get bitten.
> I recommend you move the `form` to a lambda so you don't have to
> duplicate it:
> `(let ((body (lambda () ,@form))
> (-beg- ,beg)
> (-end- ,end))
> ...)
> Another benefit is that by moving `form` outside of the `let*`, you
> won't need to use gensym/make-symbol nor obfuscated names.
> I'd also recommend you check that `beg` hasn't changed position and that
> the distance between end-marker and point-max remained the same.
> >> Maybe combine-change-calls should also combine all those changes on the
> >> undo-list into a big "delete+insert" (of course, it could also try and
> >> keep the undo granularity but mark those undo entries so that they're
> >> undone within their own combine-change-calls).
> > :-) Either of those would be quite a project, but possibly worth doing.
> Replacing the entries with a pair of delete+insert should be
> pretty easy. Something like
> (let ((old-buffer-undo-list buffer-undo-list)
> (orig-text (buffer-substring beg end)))
> ...
> (setq buffer-undo-list
> `((,(marker-position end-marker) ,beg)
> (,orig-text . ,beg)
> . ,old-buffer-undo-list)))
> modulo sanity checks (i.e. don't do it if undo is disabled and don't do
> it if old-buffer-undo-list is not within buffer-undo-list any more).
I'm experimenting with a different strategy: surrounding the mass of
elements in buffer-undo-list with a `(combine-change-begin ,beg ,end)
and a `(combine-change-end ,beg ,end). This is less violent to the undo
mechanism, for example, still permitting programs to analyse the undo
list.
primitive-undo, when it meets the latter of these, calls
before-change-functions, binds inhibit-modification-hooks to t and calls
itself recursively. This recursive invocation is terminated by the
combine-change-begin, after-change-functions being called immediately on
return.
The two arms inserted into the pcase form in primitive-undo look like:
(`(combine-change-end
,(and beg (pred integerp))
,(and end (pred integerp)))
(save-excursion
(run-hook-with-args 'before-change-functions beg end))
(setq old-len (- end beg))
(let ((inhibit-modification-hooks t))
(setq list (primitive-undo 1 list))))
(`(combine-change-begin
,(and beg (pred integerp))
,(and end (pred integerp)))
(if old-len
;; Non-nested invocation of `primitive-undo'.
(save-excursion
(run-hook-with-args 'after-change-functions beg end old-len)
(setq old-len nil))
;; Nested invocation of `primitive-undo'. Push the element back
;; on the list, and push nil to terminate this invocation.
(push next list)
(push nil list)))
(where `old-len' is an extra local variable bound to nil in the
surrounding `let' form).
The current version of combine-change-calls, incorporating (at least
most of) your suggestions now looks like:
(defmacro combine-change-calls (beg end &rest form)
`(let* ((-beg- ,beg)
(-end- ,end)
(body (lambda () ,@form))
(end-marker (copy-marker -end-)))
(if inhibit-modification-hooks
(funcall body)
(run-hook-with-args 'before-change-functions -beg- -end-)
(unless (eq buffer-undo-list t)
(push `(combine-change-begin ,-beg- ,-end-) buffer-undo-list))
(unwind-protect
(let ((inhibit-modification-hooks t))
(funcall body))
(unless (eq buffer-undo-list t)
(push `(combine-change-end ,-beg- ,(marker-position end-marker))
buffer-undo-list)))
(run-hook-with-args 'after-change-functions
beg (marker-position end-marker)
(- -end- -beg-)))))
This makes undo blindingly fast after a large comment-region operation.
It doesn't always leave point in the right place (I understand why -
it's the C function record_point failing to record point because the top
element of buffer-undo-list is no longer nil; it's a
combine-change-begin list).
Do you have any more helpful suggestions for this idea?
Basically, the combine-change-calls idea works. Given enough
encouragement, I will get my disorganised changes into a proper patch
with documentation, with a view to pushing it to master.
> Stefan
--
Alan Mackenzie (Nuremberg, Germany).
- An idea: combine-change-calls, Alan Mackenzie, 2018/03/24
- Re: An idea: combine-change-calls, Stefan Monnier, 2018/03/24
- Re: An idea: combine-change-calls, Alan Mackenzie, 2018/03/25
- Re: An idea: combine-change-calls, Stefan Monnier, 2018/03/25
- Re: An idea: combine-change-calls,
Alan Mackenzie <=
- Re: An idea: combine-change-calls, Stefan Monnier, 2018/03/26
- Re: An idea: combine-change-calls, Alan Mackenzie, 2018/03/27
- Re: An idea: combine-change-calls, Stefan Monnier, 2018/03/27
- Re: An idea: combine-change-calls, Alan Mackenzie, 2018/03/27
- Re: An idea: combine-change-calls, Stefan Monnier, 2018/03/27
- Re: An idea: combine-change-calls, Alan Mackenzie, 2018/03/28
- Re: An idea: combine-change-calls, Stefan Monnier, 2018/03/28
- Re: An idea: combine-change-calls, Alan Mackenzie, 2018/03/29
- Re: An idea: combine-change-calls, Stefan Monnier, 2018/03/29
- Re: An idea: combine-change-calls, Alan Mackenzie, 2018/03/29