bug#65432: 30.0.50; jerky image movements when zoomed

bug#65432: 30.0.50; jerky image movements when zoomed

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Hi,

When opening a rather big image into a quite big Emacs window, movements
(C-n, C-p, C-f, C-b) are smooth at original image size but are jerky
whenever there is some zooming (in or out) involved.

Recipe:
        - emacs -Q
        - 'C-x C-f' "a big image.jpg"
        - 's o' (image-transform-reset-to-original)
        - keep 'C-n' pressed, keep 'C-f' pressed -> movements are smooth
        - 'i -' (image-decrease-size)
        - keep 'C-n' pressed, keep 'C-f' pressed -> movements are jerky

Best regards,


In GNU Emacs 30.0.50 (build 2, x86_64-unknown-openbsd7.3, cairo version
 1.17.8) of 2023-08-20 built on computer
Repository revision: 321f6bd5722921175ac3dc8859daca74dbe3de6a
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101006
System Description: OpenBSD computer 7.3 GENERIC.MP#1125 amd64

Configured using:
 'configure --prefix=/home/manuel/emacs --bindir=/home/manuel/bin
 --with-x-toolkit=no --with-toolkit-scroll-bars=no --without-sound
 --without-compress-install CPPFLAGS=-I/usr/local/include
 LDFLAGS=-L/usr/local/lib'

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LCMS2 LIBOTF LIBXML2 MODULES NOTIFY KQUEUE OLDXMENU PDUMPER PNG RSVG
SQLITE3 THREADS TIFF TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM ZLIB

Important settings:
  value of $LC_ALL: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Dired by name

Minor modes in effect:
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  display-time-mode: t
  display-battery-mode: t
  server-mode: t
  override-global-mode: t
  repeat-mode: t
  desktop-save-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  buffer-read-only: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
/home/manuel/.emacs.d/elpa/ef-themes-1.3.0/theme-loaddefs hides /home/manuel/emacs/share/emacs/30.0.50/lisp/theme-loaddefs

Features:
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xcb-ewmh xcb-icccm xcb xcb-xproto xcb-types xcb-debug server
modus-operandi-theme modus-themes zone speed-type url-http url-auth
url-gw nsm compat ytdious mingus libmpdee reporter edebug debug
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rust-mode-autoloads s-autoloads speed-type-autoloads
transmission-autoloads tree-mode-autoloads visual-fill-column-autoloads
with-editor-autoloads info compat-autoloads ytdious-autoloads package
browse-url url url-proxy url-privacy url-expand url-methods url-history
url-cookie generate-lisp-file url-domsuf url-util mailcap url-handlers
url-parse auth-source cl-seq eieio eieio-core cl-macs password-cache
json subr-x map byte-opt gv bytecomp byte-compile url-vars cl-loaddefs
cl-lib rmc iso-transl tooltip cconv eldoc paren electric uniquify
ediff-hook vc-hooks lisp-float-type elisp-mode mwheel term/x-win x-win
term/common-win x-dnd touch-screen tool-bar dnd fontset image regexp-opt
fringe tabulated-list replace newcomment text-mode lisp-mode prog-mode
register page tab-bar menu-bar rfn-eshadow isearch easymenu timer select
scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors
frame minibuffer nadvice seq simple cl-generic indonesian philippine
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 emoji-zwj charscript
charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp
files window text-properties overlay sha1 md5 base64 format env
code-pages mule custom widget keymap hashtable-print-readable backquote
threads dbusbind kqueue lcms2 dynamic-setting system-font-setting
font-render-setting cairo xinput2 x multi-tty move-toolbar
make-network-process emacs)

Memory information:
((conses 16 689448 94950) (symbols 48 55830 3)
 (strings 32 176732 10415) (string-bytes 1 5672352)
 (vectors 16 104965) (vector-slots 8 2176605 163884)
 (floats 8 557 160) (intervals 56 20368 0) (buffers 992 90))

-- 
Manuel Giraud

bug#65432: 30.0.50; jerky image movements when zoomed

[Eli Zaretskii]

> Date: Mon, 21 Aug 2023 16:45:31 +0200
> From:  Manuel Giraud via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> When opening a rather big image into a quite big Emacs window, movements
> (C-n, C-p, C-f, C-b) are smooth at original image size but are jerky
> whenever there is some zooming (in or out) involved.
> 
> Recipe:
>         - emacs -Q
>         - 'C-x C-f' "a big image.jpg"
>         - 's o' (image-transform-reset-to-original)
>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are smooth
>         - 'i -' (image-decrease-size)
>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are jerky

I cannot reproduce this, on MS-Windows.  I see no difference between
"jerkyness" of motion commands before and after 'i -'.

bug#65432: 30.0.50; jerky image movements when zoomed

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Mon, 21 Aug 2023 16:45:31 +0200
>> From:  Manuel Giraud via "Bug reports for GNU Emacs,
>>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>> 
>> When opening a rather big image into a quite big Emacs window, movements
>> (C-n, C-p, C-f, C-b) are smooth at original image size but are jerky
>> whenever there is some zooming (in or out) involved.
>> 
>> Recipe:
>>         - emacs -Q
>>         - 'C-x C-f' "a big image.jpg"
>>         - 's o' (image-transform-reset-to-original)
>>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are smooth
>>         - 'i -' (image-decrease-size)
>>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are jerky
>
> I cannot reproduce this, on MS-Windows.  I see no difference between
> "jerkyness" of motion commands before and after 'i -'.

This is a known inefficiency with Cairo's implementation of affine
transforms.  AFAICT, Cairo performs the transform on the CPU, which is
aggravated by uploading the complete bitmap to the X server every time
the image is displayed.

Building without Cairo should induce Emacs to utilize XRender transforms
instead, ameliorating this problem.

bug#65432: 30.0.50; jerky image movements when zoomed

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Po Lu <luangruo@yahoo.com> writes:

[...]

>> I cannot reproduce this, on MS-Windows.  I see no difference between
>> "jerkyness" of motion commands before and after 'i -'.
>
> This is a known inefficiency with Cairo's implementation of affine
> transforms.  AFAICT, Cairo performs the transform on the CPU, which is
> aggravated by uploading the complete bitmap to the X server every time
> the image is displayed.
>
> Building without Cairo should induce Emacs to utilize XRender transforms
> instead, ameliorating this problem.

Thanks, I'm going to try without Cairo.  But would it be possible to
have Emacs using cairo for everything except for raster images?
-- 
Manuel Giraud

bug#65432: 30.0.50; jerky image movements when zoomed

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

So I have built "--without-cairo" and it fixes this issue (movements are
smooth whatever the zoom).  But now I have the following warning when
building:

configure:55221: WARNING: This configuration uses libXft, which has a number of
    font rendering issues, and is being considered for removal in the
    next release of Emacs.  Please consider using Cairo graphics +
    HarfBuzz text shaping instead (they are auto-detected if the
    relevant development headers are installed).

So giving up on cairo does not seem like a good idea :-/
-- 
Manuel Giraud

bug#65432: 30.0.50; jerky image movements when zoomed

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Manuel Giraud <manuel@ledu-giraud.fr>,  65432@debbugs.gnu.org
> Date: Tue, 22 Aug 2023 10:59:22 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> Date: Mon, 21 Aug 2023 16:45:31 +0200
> >> From:  Manuel Giraud via "Bug reports for GNU Emacs,
> >>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> >> 
> >> When opening a rather big image into a quite big Emacs window, movements
> >> (C-n, C-p, C-f, C-b) are smooth at original image size but are jerky
> >> whenever there is some zooming (in or out) involved.
> >> 
> >> Recipe:
> >>         - emacs -Q
> >>         - 'C-x C-f' "a big image.jpg"
> >>         - 's o' (image-transform-reset-to-original)
> >>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are smooth
> >>         - 'i -' (image-decrease-size)
> >>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are jerky
> >
> > I cannot reproduce this, on MS-Windows.  I see no difference between
> > "jerkyness" of motion commands before and after 'i -'.
> 
> This is a known inefficiency with Cairo's implementation of affine
> transforms.  AFAICT, Cairo performs the transform on the CPU, which is
> aggravated by uploading the complete bitmap to the X server every time
> the image is displayed.
> 
> Building without Cairo should induce Emacs to utilize XRender transforms
> instead, ameliorating this problem.

Should this be in PROBLEMS?

bug#65432: 30.0.50; jerky image movements when zoomed

[Eli Zaretskii]

Ping!  Should we mention this issue in PROBLEMS?

> Cc: 65432@debbugs.gnu.org, manuel@ledu-giraud.fr
> Date: Sat, 26 Aug 2023 10:58:56 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > From: Po Lu <luangruo@yahoo.com>
> > Cc: Manuel Giraud <manuel@ledu-giraud.fr>,  65432@debbugs.gnu.org
> > Date: Tue, 22 Aug 2023 10:59:22 +0800
> > 
> > Eli Zaretskii <eliz@gnu.org> writes:
> > 
> > >> Date: Mon, 21 Aug 2023 16:45:31 +0200
> > >> From:  Manuel Giraud via "Bug reports for GNU Emacs,
> > >>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> > >> 
> > >> When opening a rather big image into a quite big Emacs window, movements
> > >> (C-n, C-p, C-f, C-b) are smooth at original image size but are jerky
> > >> whenever there is some zooming (in or out) involved.
> > >> 
> > >> Recipe:
> > >>         - emacs -Q
> > >>         - 'C-x C-f' "a big image.jpg"
> > >>         - 's o' (image-transform-reset-to-original)
> > >>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are smooth
> > >>         - 'i -' (image-decrease-size)
> > >>         - keep 'C-n' pressed, keep 'C-f' pressed -> movements are jerky
> > >
> > > I cannot reproduce this, on MS-Windows.  I see no difference between
> > > "jerkyness" of motion commands before and after 'i -'.
> > 
> > This is a known inefficiency with Cairo's implementation of affine
> > transforms.  AFAICT, Cairo performs the transform on the CPU, which is
> > aggravated by uploading the complete bitmap to the X server every time
> > the image is displayed.
> > 
> > Building without Cairo should induce Emacs to utilize XRender transforms
> > instead, ameliorating this problem.
> 
> Should this be in PROBLEMS?
> 
> 
> 
> 

bug#65432: 30.0.50; jerky image movements when zoomed

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Eli Zaretskii <eliz@gnu.org> writes:

> Ping!  Should we mention this issue in PROBLEMS?

I think so.  I will write an entry.

bug#65432: 30.0.50; jerky image movements when zoomed

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: 65432@debbugs.gnu.org,  manuel@ledu-giraud.fr
> Date: Sat, 02 Sep 2023 15:35:05 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Ping!  Should we mention this issue in PROBLEMS?
> 
> I think so.  I will write an entry.

I see you've written it on the emacs-29 branch, so I'm now closing
this bug.

Thanks.

bug#65432: 30.0.50; jerky image movements when zoomed

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Po Lu <luangruo@yahoo.com>
>> Cc: 65432@debbugs.gnu.org,  manuel@ledu-giraud.fr
>> Date: Sat, 02 Sep 2023 15:35:05 +0800
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> > Ping!  Should we mention this issue in PROBLEMS?
>> 
>> I think so.  I will write an entry.
>
> I see you've written it on the emacs-29 branch, so I'm now closing
> this bug.

Ok.  I'm currently using "--without-cairo" to fix this issue.  FTR, Po,
what is the drawback of not using cairo in Emacs?  Thanks.
-- 
Manuel Giraud

bug#65432: 30.0.50; jerky image movements when zoomed

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Manuel Giraud <manuel@ledu-giraud.fr> writes:

> Ok.  I'm currently using "--without-cairo" to fix this issue.  FTR, Po,
> what is the drawback of not using cairo in Emacs?  Thanks.

Color fonts will cease functioning, which shouldn't affect those who
don't rely on Emoji display for their work.  There is also word of some
crashes with seldom-encountered fonts on old versions of Xft.