bug#59481: 29.0.50; c-ts-mode doesn't play nicely with pixel-scroll-precision-mode

bug#59481: 29.0.50; c-ts-mode doesn't play nicely with pixel-scroll-precision-mode

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

Enable pixel-scroll-precision-mode, then open src/xterm.c.  Go to line
3439, enable c-ts-mode, and scroll up _with a trackpad_ until line 1675
becomes visible near the start of the window.  Finally, go down to line
1817: brackets will become randomly fontified in the error face.

In addition, I was expecting c-ts-mode to be quite a lot faster
fontifying during precision scrolling, but it is currently as slow as CC
Mode.  I think that is almost definitely a bug somewhere in our
tree-sitter fontification code, since emacs-lisp-mode fontifies much
faster.

In GNU Emacs 29.0.50 (build 243, x86_64-pc-linux-gnu) of 2022-11-22
 built on trinity
Repository revision: 350918e7be82fca046911073b360518173169255
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101099
System Description: Fedora Linux 37 (Workstation Edition)

Configured using:
 'configure --with-x --with-x-toolkit=no --without-cairo
 --with-dumping=unexec --cache-file=/tmp/ccache'

Configured features:
ACL DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON LCMS2
LIBSELINUX LIBSYSTEMD LIBXML2 MODULES NOTIFY INOTIFY OLDXMENU PNG RSVG
SECCOMP SOUND SQLITE3 THREADS TIFF TREE_SITTER UNEXEC WEBP X11 XDBE XFT
XIM XINPUT2 XPM ZLIB

Important settings:
  value of $LANG: en_GB.utf8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: C

Minor modes in effect:
  pixel-scroll-precision-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: 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:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils warnings icons c-ts-mode misearch
multi-isearch add-log log-view pcvs-util vc time-date cus-start cus-load
pixel-scroll cua-base ring subr-x vc-git diff-mode easy-mmode
vc-dispatcher bug-reference byte-opt gv bytecomp byte-compile find-func
cc-langs cc-mode cc-fonts cc-guess cc-menus cc-cmds cc-styles cc-align
cc-engine cc-vars cc-defs cl-extra shortdoc text-property-search
thingatpt help-fns radix-tree help-mode sh-script rx smie treesit cl-seq
cl-loaddefs cl-lib executable 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 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 inotify lcms2
dynamic-setting system-font-setting font-render-setting xinput2 x
multi-tty make-network-process emacs)

Memory information:
((conses 16 220297 20026)
 (symbols 48 27211 0)
 (strings 32 52112 2076)
 (string-bytes 1 1435642)
 (vectors 16 28133)
 (vector-slots 8 881343 40772)
 (floats 8 194 659)
 (intervals 56 19633 0)
 (buffers 992 18))

bug#59481: 29.0.50; c-ts-mode doesn't play nicely with pixel-scroll-precision-mode

[Yuan Fu]

Po Lu <luangruo@yahoo.com> writes:

> Enable pixel-scroll-precision-mode, then open src/xterm.c.  Go to line
> 3439, enable c-ts-mode, and scroll up _with a trackpad_ until line 1675
> becomes visible near the start of the window.  Finally, go down to line
> 1817: brackets will become randomly fontified in the error face.
>
> In addition, I was expecting c-ts-mode to be quite a lot faster
> fontifying during precision scrolling, but it is currently as slow as CC
> Mode.  I think that is almost definitely a bug somewhere in our
> tree-sitter fontification code, since emacs-lisp-mode fontifies much
> faster.

How do you decide if the scrolling is fast or not? Maybe you are seeing
palpable lags? I’m using macOS with the builtin trackpad, and scrolling
is pretty snappy. Maybe this only happens on Linux? I’m also seeing
random error faces (albeit not on brackets), could this relate to some
particular way pixel-scrolling works? Does pixel-scrolling do anything
special comparing to normal scrolling when fontifying text?

Thanks,
Yuan

bug#59481: 29.0.50; c-ts-mode doesn't play nicely with pixel-scroll-precision-mode

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

Yuan Fu <casouri@gmail.com> writes:

> How do you decide if the scrolling is fast or not? Maybe you are seeing
> palpable lags? I’m using macOS with the builtin trackpad, and scrolling
> is pretty snappy. Maybe this only happens on Linux? I’m also seeing
> random error faces (albeit not on brackets), could this relate to some
> particular way pixel-scrolling works? Does pixel-scrolling do anything
> special comparing to normal scrolling when fontifying text?

Likely not, it just uses the normal jit-lock fontification like everyone
else.  I suggest comparing the speed of scrolling with that of
emacs-lisp-mode, and maybe setting ns-scroll-event-delta-factor to 3 or
4.

Thanks.