From: Alan Mackenzie <acm@muc.de>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: Hannu Koivisto <azure@iki.fi>, emacs-devel@gnu.org
Subject: Re: First fontification of a buffer happens before font lock is fully initialised.
Date: Sat, 4 Feb 2012 12:03:19 +0000 [thread overview]
Message-ID: <20120204120319.GC3347@acm.acm> (raw)
In-Reply-To: <jwvfwf31c3y.fsf-monnier+emacs@gnu.org>
Hello, Stefan
On Wed, Jan 25, 2012 at 08:43:48PM -0500, Stefan Monnier wrote:
> >> > This situation was found and analysed by Hannu Koivisto after CC Mode
> >> > crashed for this reason on a C++ buffer. Why it doesn't happen for
> >> > every CC Mode buffer is not yet clear.
> >> I think the behavior depends on the use of font-lock-support-mode.
> >> With jit-lock, fontification takes place after running the mode-hook,
> >> whereas without it, fontification takes place before.
> > Surely this cannot be
> I'm pretty sure this is the source of the difference.
> > the hooks are run at the end of the define-minor-mode expansion no
> > matter what.
> Yes, but fontification can take place even later, depending on
> font-lock-support-mode.
> > Surely the hooks are not being run twice.
> No, indeed, they should only be run once.
> > Though I admit I haven't tracked down the stages in initialising
> > jit-lock-mode.
> jit-lock postpones fontification to whenever the text is actually
> displayed, i.e. much later than initialization; it may very well never
> fontify any part of the text at all, if the buffer is never displayed.
> > So do you agree that the code should be changed so that
> > fontification always happens after running the mode-hook?
> Yes, I agree. This was the behavior in Emacs-20, and is also the
> behavior with jit-lock (i.e. the default behavior). I'm not sure what's
> the best way to get that result, tho: adding yet-another keyword to
> define-minor-mode is something I'd rather avoid.
I can only see one other way to deal with this: that is to write
`font-lock-mode' explicitly; or rather, expand the macro by hand, tidy it
up, and move the `run-hooks'.
I've done this in the patch below. To see the difference between before
and after, do
emacs -Q
M-: (setq font-lock-support-mode nil)
C-c C-f random.c
Before the change, an error is thrown. After the change, it works.
Should I commit this patch?
=== modified file 'lisp/font-core.el'
*** lisp/font-core.el 2012-01-19 07:21:25 +0000
--- lisp/font-core.el 2012-02-04 11:59:45 +0000
***************
*** 87,93 ****
;; The mode for which font-lock was initialized, or nil if none.
(defvar font-lock-major-mode)
! (define-minor-mode font-lock-mode
"Toggle syntax highlighting in this buffer (Font Lock mode).
With a prefix argument ARG, enable Font Lock mode if ARG is
positive, and disable it otherwise. If called from Lisp, enable
--- 87,100 ----
;; The mode for which font-lock was initialized, or nil if none.
(defvar font-lock-major-mode)
! (defvar font-lock-mode nil
! "Non-nil if Font-Lock mode is enabled.
! Use the command `font-lock-mode' to change this variable.")
! (make-variable-buffer-local 'font-lock-mode)
!
! ;; Note: `define-minor-mode' cannot be used here, since the mode hooks
! ;; need to be run before the first fontification of a buffer.
! (defun font-lock-mode (&optional arg)
"Toggle syntax highlighting in this buffer (Font Lock mode).
With a prefix argument ARG, enable Font Lock mode if ARG is
positive, and disable it otherwise. If called from Lisp, enable
***************
*** 137,152 ****
The above is the default behavior of `font-lock-mode'; you may specify
your own function which is called when `font-lock-mode' is toggled via
`font-lock-function'. "
! nil nil nil
! ;; Don't turn on Font Lock mode if we don't have a display (we're running a
! ;; batch job) or if the buffer is invisible (the name starts with a space).
! (when (or noninteractive (eq (aref (buffer-name) 0) ?\s))
! (setq font-lock-mode nil))
! (funcall font-lock-function font-lock-mode)
! ;; Arrange to unfontify this buffer if we change major mode later.
! (if font-lock-mode
! (add-hook 'change-major-mode-hook 'font-lock-change-mode nil t)
! (remove-hook 'change-major-mode-hook 'font-lock-change-mode t)))
;; Get rid of fontification for the old major mode.
;; We do this when changing major modes.
--- 144,185 ----
The above is the default behavior of `font-lock-mode'; you may specify
your own function which is called when `font-lock-mode' is toggled via
`font-lock-function'. "
! (interactive (list (or current-prefix-arg 'toggle)))
! (let ((last-message (current-message)))
! (setq font-lock-mode
! (cond ((eq arg 'toggle)
! (not font-lock-mode))
! (arg (> (prefix-numeric-value arg) 0))
! (t (if (null font-lock-mode)
! t
! (message "Toggling %s off; better pass an explicit argument."
! 'font-lock-mode)
! nil))))
!
! (when (or noninteractive (eq (aref (buffer-name) 0) 32))
! (setq font-lock-mode nil))
!
! (if font-lock-mode
! (add-hook 'change-major-mode-hook 'font-lock-change-mode nil t)
! (remove-hook 'change-major-mode-hook 'font-lock-change-mode t))
! (run-hooks 'font-lock-mode-hook
! (if font-lock-mode
! 'font-lock-mode-on-hook
! 'font-lock-mode-off-hook))
! (funcall font-lock-function font-lock-mode)
! (if (called-interactively-p 'any)
! (progn nil
! (unless (and (current-message)
! (not (equal last-message (current-message))))
! (message "Font-Lock mode %sabled"
! (if font-lock-mode "en" "dis"))))))
!
! (force-mode-line-update) font-lock-mode)
!
! :autoload-end
! (add-minor-mode 'font-lock-mode nil
! (if (boundp 'font-lock-mode-map)
! font-lock-mode-map))
;; Get rid of fontification for the old major mode.
;; We do this when changing major modes.
> Stefan
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2012-02-04 12:03 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-25 12:48 First fontification of a buffer happens before font lock is fully initialised Alan Mackenzie
2012-01-25 17:46 ` Stefan Monnier
2012-01-25 18:26 ` Alan Mackenzie
2012-01-25 19:22 ` Hannu Koivisto
2012-01-25 20:22 ` Alan Mackenzie
2012-01-26 1:43 ` Stefan Monnier
2012-01-26 10:58 ` Alan Mackenzie
2012-02-04 12:03 ` Alan Mackenzie [this message]
2012-02-06 1:39 ` Stefan Monnier
2012-02-07 10:10 ` Alan Mackenzie
2012-02-07 18:02 ` Stefan Monnier
2012-02-08 21:43 ` Alan Mackenzie
2012-02-10 14:27 ` Stefan Monnier
2012-02-23 11:39 ` Alan Mackenzie
2012-02-23 14:34 ` Stefan Monnier
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