Received: (at 45054) by debbugs.gnu.org; 5 Dec 2020 16:18:38 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Dec 05 11:18:38 2020 Received: from localhost ([127.0.0.1]:48088 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1klaGb-0003qR-O6 for submit <at> debbugs.gnu.org; Sat, 05 Dec 2020 11:18:37 -0500 Received: from eggs.gnu.org ([209.51.188.92]:54578) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1klaGa-0003q8-EW for 45054 <at> debbugs.gnu.org; Sat, 05 Dec 2020 11:18:36 -0500 Received: from fencepost.gnu.org ([2001:470:142:3::e]:47656) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1klaGV-000117-5o; Sat, 05 Dec 2020 11:18:31 -0500 Received: from [176.228.60.248] (port=4553 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from <eliz@HIDDEN>) id 1klaGU-00016j-8d; Sat, 05 Dec 2020 11:18:31 -0500 Date: Sat, 05 Dec 2020 18:18:15 +0200 Message-Id: <83sg8kb514.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Zack Weinberg <zackw@HIDDEN> In-Reply-To: <CAKCAbMhCSesZAM5WMFp_X+CAYCOfDn5fMu2kJQ9JHyDOwZb=7w@HIDDEN> (message from Zack Weinberg on Sat, 5 Dec 2020 10:54:57 -0500) Subject: Re: bug#45054: 27.1; Can get point into the middle of a run of characters with a replacing display spec References: <CAKCAbMhCSesZAM5WMFp_X+CAYCOfDn5fMu2kJQ9JHyDOwZb=7w@HIDDEN> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 45054 Cc: 45054 <at> debbugs.gnu.org X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > From: Zack Weinberg <zackw@HIDDEN> > Date: Sat, 5 Dec 2020 10:54:57 -0500 > > \ ;; \| > u00B6 ;; \u00B6| > C-a ;; |\u00B6 > M-x fold-demo-mode ;; |¶ > C-d ;; |u00B6 > \ ;; ¶| > x ;; \x|u00B6 > > The bug happens when you type \ for the second time. The font-lock rule > matches again, “\u00B6” is converted to “¶”, and the *visible cursor* is > displaced to after the “¶”, but *point* is still where it was, between > the invisible \ and u characters. Any self-inserting character, like > the ‘x’ shown in the recipe, will be inserted at the actual location of > point, instead of the position of the visible cursor. In the demo, this > causes the font-lock rule to stop matching again. > > Any cursor-motion command while Emacs is in this state, will put point > back in sync with the visible cursor; this can lead to odd but harmless > phenomena, for instance a single C-f doesn’t appear to do anything, > instead of moving the cursor to the next line like it normally would. > (Because point moves within the hidden run of characters, and then gets > displaced to the end of the run, where the visible cursor already is.) > > Questions: > > 1. Is this indeed a bug in Emacs? Probably a bug in adjust_point_for_property. Try your recipe after setting global-disable-point-adjustment non-nil. > 2. Assuming it is, can you suggest a workaround? I’m hoping for a > viable solution within my code that’s compatible at least as far back > as Emacs 24. A workaround in Lisp? Try making the affected text, or some of it, invisible, i.e. give it the 'invisible' text property as well. (I didn't try to test this solution, so I cannot promise it will work.) > 3. I think it would be better UI if the C-d in the recipe deleted the > entire run of text that’s getting hidden (more generally, deletion > commands should behave as if the ¶ is really what’s in the buffer). > I can’t figure out how to implement that, can you suggest anything? Why can't you delete every character around point that has this special property? > 4. Is there a better way to do this sort of visual replacement of runs > of text? This is the first time I’ve done any serious elisp > programming, I might have missed something. Sounds the right way to me (modulo making the text invisible).
bug-gnu-emacs@HIDDEN:bug#45054; Package emacs.
Full text available.Received: (at 45054) by debbugs.gnu.org; 5 Dec 2020 15:59:41 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Dec 05 10:59:41 2020 Received: from localhost ([127.0.0.1]:48060 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1klZyH-0003KJ-CQ for submit <at> debbugs.gnu.org; Sat, 05 Dec 2020 10:59:41 -0500 Received: from mailbackend.panix.com ([166.84.1.89]:44371) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <zackw@HIDDEN>) id 1klZyF-0003KC-Ko for 45054 <at> debbugs.gnu.org; Sat, 05 Dec 2020 10:59:39 -0500 Received: from mail-ed1-f47.google.com (mail-ed1-f47.google.com [209.85.208.47]) by mailbackend.panix.com (Postfix) with ESMTPSA id 4CpDmC31p5zVr6 for <45054 <at> debbugs.gnu.org>; Sat, 5 Dec 2020 10:59:39 -0500 (EST) Received: by mail-ed1-f47.google.com with SMTP id c7so9068243edv.6 for <45054 <at> debbugs.gnu.org>; Sat, 05 Dec 2020 07:59:39 -0800 (PST) X-Gm-Message-State: AOAM5327e2cAbP09GZ52YSBSykaN4zw9hNuP8ELwe+F059lk/nT208Nr szVnIxS/j6zz55QuP2vGUTJJ7OTTYngJ+LnWrwE= X-Google-Smtp-Source: ABdhPJxeVPCaE3j8KRsE0q75Zam0OjHMIXrL4qItVpuLSjK+l39azpN5spGymvTKulU53jZykdC7cIMuopH+hucx01c= X-Received: by 2002:a05:6402:312c:: with SMTP id dd12mr12757464edb.327.1607183978546; Sat, 05 Dec 2020 07:59:38 -0800 (PST) MIME-Version: 1.0 From: Zack Weinberg <zackw@HIDDEN> Date: Sat, 5 Dec 2020 10:59:27 -0500 X-Gmail-Original-Message-ID: <CAKCAbMiOijUs2ew=aa_JtWSuOgbZyXEm5KyD0tgq1Obun5BHFA@HIDDEN> Message-ID: <CAKCAbMiOijUs2ew=aa_JtWSuOgbZyXEm5KyD0tgq1Obun5BHFA@HIDDEN> Subject: Re: 27.1; Can get point into the middle of a run of characters with a replacing display spec To: 45054 <at> debbugs.gnu.org Content-Type: text/plain; charset="UTF-8" X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 45054 X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) I forgot to mention that nothing changes if I also have font-lock apply the 'cursor-intangible property to the hidden run of text.
bug-gnu-emacs@HIDDEN:bug#45054; Package emacs.
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Subject: 27.1; Can get point into the middle of a run of characters with a
replacing display spec
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I'm implementing a minor mode that "folds" certain strings, causing them
to be displayed as the actual single characters that they are notation
for. For purposes of this bug report, I will use the running example of
displaying C-style backslash escapes for Unicode characters as their
actual characters, e.g. \u00B6 is displayed as =C2=B6 when the mode is
active.
The mode does this by adding a font-lock keywords rule to the buffer,
that applies display properties that make each string look like it's a
single character. The documentation says that Emacs will not let point
get into the middle of a run of text that's hidden this way, and that's
mostly true, but I found a way to do it.
Starting from =E2=80=98emacs -Q=E2=80=99:
In the *scratch* buffer, evaluate the following minor mode definition;
this is a cut-down version of the real mode, that only replaces \u00B6.
(define-minor-mode fold-demo-mode
"Folding bug demo"
:init-value nil
:lighter " FD"
:keymap nil
(make-variable-buffer-local 'font-lock-extra-managed-props)
(cl-flet ((refontify ()
(save-excursion
(goto-char (point-min))
(while (re-search-forward "\\\\u00[bB]6" nil t)
(save-excursion
(font-lock-fontify-region
(match-beginning 0) (match-end 0)))))))
(let ((case-fold-search nil)
(demo-fl-rule '(("\\\\u00[bB]6" 0
'(face font-lock-string-face
display "=C2=B6")))))
(if fold-demo-mode
(progn
(push 'display font-lock-extra-managed-props)
(font-lock-add-keywords nil demo-fl-rule)
(refontify))
(font-lock-remove-keywords nil demo-fl-rule)
(refontify)
(setq font-lock-extra-managed-props
(cl-remove 'display font-lock-extra-managed-props
:count 1))))))
Then, in any convenient buffer, on an initially blank line, type the
following. I=E2=80=99ve written the recipe out as it might appear in a
keyboard-macro editing buffer, but instead of command names, the
annotations show what you see at each stage. The *visible cursor* is
indicated with a |; all other characters are real.
\ ;; \|
u00B6 ;; \u00B6|
C-a ;; |\u00B6
M-x fold-demo-mode ;; |=C2=B6
C-d ;; |u00B6
\ ;; =C2=B6|
x ;; \x|u00B6
The bug happens when you type \ for the second time. The font-lock rule
matches again, =E2=80=9C\u00B6=E2=80=9D is converted to =E2=80=9C=C2=B6=E2=
=80=9D, and the *visible cursor* is
displaced to after the =E2=80=9C=C2=B6=E2=80=9D, but *point* is still where=
it was, between
the invisible \ and u characters. Any self-inserting character, like
the =E2=80=98x=E2=80=99 shown in the recipe, will be inserted at the actual=
location of
point, instead of the position of the visible cursor. In the demo, this
causes the font-lock rule to stop matching again.
Any cursor-motion command while Emacs is in this state, will put point
back in sync with the visible cursor; this can lead to odd but harmless
phenomena, for instance a single C-f doesn=E2=80=99t appear to do anything,
instead of moving the cursor to the next line like it normally would.
(Because point moves within the hidden run of characters, and then gets
displaced to the end of the run, where the visible cursor already is.)
Questions:
1. Is this indeed a bug in Emacs?
2. Assuming it is, can you suggest a workaround? I=E2=80=99m hoping for a
viable solution within my code that=E2=80=99s compatible at least as far=
back
as Emacs 24.
3. I think it would be better UI if the C-d in the recipe deleted the
entire run of text that=E2=80=99s getting hidden (more generally, deleti=
on
commands should behave as if the =C2=B6 is really what=E2=80=99s in the =
buffer).
I can=E2=80=99t figure out how to implement that, can you suggest anythi=
ng?
4. Is there a better way to do this sort of visual replacement of runs
of text? This is the first time I=E2=80=99ve done any serious elisp
programming, I might have missed something.
Thanks for your attention,
zw
In GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.23,
cairo version 1.16.0) of 2020-11-07, modified by Debian built on
x86-ubc-01 Windowing system distributor 'The X.Org Foundation', version
11.0.12009000 System Description: Debian GNU/Linux bullseye/sid
Configured using:
'configure --build x86_64-linux-gnu --prefix=3D/usr
--sharedstatedir=3D/var/lib --libexecdir=3D/usr/lib
--localstatedir=3D/var/lib --infodir=3D/usr/share/info
--mandir=3D/usr/share/man --enable-libsystemd --with-pop=3Dyes
--enable-locallisppath=3D/etc/emacs:/usr/local/share/emacs/27.1/site-lisp:=
/usr/local/share/emacs/site-lisp:/usr/share/emacs/27.1/site-lisp:/usr/share=
/emacs/site-lisp
--with-sound=3Dalsa --without-gconf --with-mailutils --build
x86_64-linux-gnu --prefix=3D/usr --sharedstatedir=3D/var/lib
--libexecdir=3D/usr/lib --localstatedir=3D/var/lib
--infodir=3D/usr/share/info --mandir=3D/usr/share/man --enable-libsystemd
--with-pop=3Dyes
--enable-locallisppath=3D/etc/emacs:/usr/local/share/emacs/27.1/site-lisp:=
/usr/local/share/emacs/site-lisp:/usr/share/emacs/27.1/site-lisp:/usr/share=
/emacs/site-lisp
--with-sound=3Dalsa --without-gconf --with-mailutils --with-cairo
--with-x=3Dyes --with-x-toolkit=3Dgtk3 --with-toolkit-scroll-bars
'CFLAGS=3D-g -O2
-fdebug-prefix-map=3D/build/emacs-6jKC2B/emacs-27.1+1=3D.
-fstack-protector-strong -Wformat -Werror=3Dformat-security -Wall'
'CPPFLAGS=3D-Wdate-time -D_FORTIFY_SOURCE=3D2' LDFLAGS=3D-Wl,-z,relro'
Configured features:
XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND GPM DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF
ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS LIBSYSTEMD
JSON PDUMPER LCMS2 GMP
Important settings:
value of $LANG: en_US.UTF-8
value of $XMODIFIERS: @im=3Dibus
locale-coding-system: utf-8-unix
Features:
(shadow sort mail-extr emacsbug message rmc puny rfc822 mml mml-sec epa
derived epg epg-config gnus-util rmail rmail-loaddefs
text-property-search mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils help-mode server visual-regexp-steroids
visual-regexp tramp tramp-loaddefs trampver tramp-integration files-x
tramp-compat parse-time iso8601 time-date ls-lisp dired dired-loaddefs
dbus xml solarized-light-theme solarized color dash typo paren grep
cus-start cus-load erlang-start ess-site ess-toolbar ess-mouse mouseme
ess-swv ess-noweb ess-noweb-font-lock-mode ess-jags-d ess-bugs-l
essd-els ess-xls-d ess-vst-d ess-stata-mode ess-stata-lang cc-vars
cc-defs make-regexp ess-sp6w-d ess-sp5-d ess-sp4-d ess-sas-d ess-sas-l
ess-sas-a ess-s4-d ess-s3-d ess-omg-d ess-omg-l ess-arc-d ess-lsp-l
ess-sp6-d ess-dde ess-sp3-d ess-julia julia-mode cl ess-r-mode
ess-r-flymake flymake-proc flymake warnings thingatpt ess-r-xref xref
project ess-trns ess-r-package shell pcomplete ess-r-syntax
ess-r-completion ess-roxy ess-rd essddr noutline outline easy-mmode
hideshow ess-s-lang ess-help info ess-mode ess ess-noweb-mode ess-inf
ess-tracebug advice format-spec ess-generics compile ess-utils ido
ess-custom executable comint ansi-color ring go-mode-autoloads package
easymenu browse-url url-handlers url-parse auth-source cl-seq eieio
eieio-core cl-macs eieio-loaddefs password-cache json subr-x map
url-vars seq byte-opt gv bytecomp byte-compile cconv cl-loaddefs cl-lib
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode elisp-mode
lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch
timer select scroll-bar mouse jit-lock font-lock syntax facemenu
font-core term/tty-colors frame minibuffer cl-generic cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads dbusbind
inotify lcms2 dynamic-setting system-font-setting font-render-setting
cairo move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)
Zack Weinberg <zackw@HIDDEN>:bug-gnu-emacs@HIDDEN.
Full text available.bug-gnu-emacs@HIDDEN:bug#45054; Package emacs.
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