From: Paul Pogonyshev <pogonyshev@gmail.com>
To: Emacs developers <emacs-devel@gnu.org>
Subject: Signal `quit' in a `font-lock-fontify-region-function'
Date: Fri, 17 May 2019 00:20:04 +0200 [thread overview]
Message-ID: <CAG7Bpaon-bQfYLzbDTNPR0Fe-1i1y49dLxmek34-=UBSa1R+Kg@mail.gmail.com> (raw)
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Hi,
I'm having the following, unfortunately unreproducible problem: inside a
custom font-locking function condition `quit' _sometimes_ cannot be
triggered with C-g. I'm sure it has nothing to do with `inhibit-quit'. For
the same function in one Emacs instance it is triggerable, in another ---
not. If in a certain instance it "breaks" (i.e. C-g no longer triggers
`quit'), it seems to stay broken forever.
This is notoriously difficult to investigate. I came up with the following
pseudo-mode (usage: M-x pretend-fontification-mode RET in a large buffer):
(define-derived-mode pretend-fontification-mode nil "PRETEND-FONTIFICATION"
"..."
(setq font-lock-defaults '(nil))
(set (make-local-variable 'font-lock-fontify-region-function)
(lambda (from to _verbose)
;; (message ...) doesn't seem to do anything
(with-current-buffer "*Messages*" (with-silent-modifications
(insert (format "\nPRETEND-FONTIFYING %s-%s\n" from to))))
(let (x)
(dotimes (k 10000000) ; long delay in pure Lisp, i.e. not
`sleep-for'
(setq x k))))))
but as I said it is not reproducible: sometimes mashing C-g results in the
following in *Messages* buffer:
Error during redisplay: (jit-lock-function ##) signaled (quit)
sometimes it doesn't. I also tried `(condition-case ... (quit ...))' inside
font-locking function, but result is the same: sometimes the handler is
triggered, sometimes it is not and I cannot work out any pattern. I also
tried printing out values that could be relevant (inhibit-quit, quit-flag,
(input-pending-p), unread-command-events), but they appear to be the same
regardless of whether `quit' is still triggerable or not.
Does anyone has any idea what's going on?
Paul
P.S.: I'm not subscribed to the list, please CC answers to me.
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next reply other threads:[~2019-05-16 22:20 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-16 22:20 Paul Pogonyshev [this message]
2019-05-16 23:20 ` Signal `quit' in a `font-lock-fontify-region-function' Stefan Monnier
-- strict thread matches above, loose matches on Subject: below --
2019-05-28 16:24 Paul Pogonyshev
2019-05-28 17:50 ` Stefan Monnier
2019-05-28 18:14 ` Paul Pogonyshev
2019-05-28 18:24 ` Stefan Monnier
2019-06-29 17:50 Paul Pogonyshev
2019-06-29 21:26 ` Stefan Monnier
2019-06-29 23:49 ` Paul Pogonyshev
2019-06-30 0:18 ` Stefan Monnier
2019-06-30 10:51 ` Paul Pogonyshev
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