Re: Run `M-x list-input-methods` and then scroll down the screen in input method panel using the mouse or arrow key will cause Emacs unresponsive for about 1 minite.

[Eli Zaretskii <eliz@gnu.org>]

> From: Hongyi Zhao <hongyi.zhao@gmail.com>
> Date: Sat, 19 Jun 2021 18:48:28 +0800
> Cc: emacs-devel@gnu.org
> 
> The slow self compiled git master version:
> 
> system-configuration:
> 
> "x86_64-pc-linux-gnu"
> 
> system-configuration-options:
> 
> "--without-m17n-flt"
> 
> 
> system-configuration-features:
> 
> "ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ
> JPEG JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 MODULES NOTIFY
> INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS TIFF
> TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM GTK3 ZLIB"
> 
> The fast prebuilt version shipped with the apt repo:
> 
> system-configuration:
> 
> "x86_64-pc-linux-gnu"
> 
> 
> system-configuration-options:
> 
> "--build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
> --libexecdir=/usr/lib --localstatedir=/var/lib
> --infodir=/usr/share/info --mandir=/usr/share/ma\
>     n --enable-libsystemd --with-pop=yes
> --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26\
>     .3/site-lisp:/usr/share/emacs/site-lisp --with-sound=alsa
> --without-gconf --with-mailutils --build x86_64-linux-gnu
> --prefix=/usr --sharedstatedir=/var/lib --lib\
>     execdir=/usr/lib --localstatedir=/var/lib
> --infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd
> --with-pop=yes --enable-locallisppath=/etc/emacs:\
>     /usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.3/site-lisp:/usr/share/emacs/site-lisp
> --with-sound=alsa --without-gco\
>     nf --with-mailutils --with-x=no --without-gsettings 'CFLAGS=-g -O2
> -fdebug-prefix-map=/build/emacs-mEZBk7/emacs-26.3+1=.
> -fstack-protector-strong -Wformat -Werro\
>     r=format-security -Wall' 'CPPFLAGS=-Wdate-time
> -D_FORTIFY_SOURCE=2' 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro'"
> 
> 
> system-configuration-features:
> 
>  "JPEG SOUND GPM DBUS NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 ZLIB XIM
> THREADS LIBSYS\
>     TEMD LCMS2"

The fast version is an optimized build, the slow one is unoptimized.
That explains at least part of the slowness.  The fast version also
doesn't include any text-shaping engine, which might speed up Emacs,
but prevents it from correctly displaying complex scripts.

What are the Emacs versions of the two builds?