from Emacs 29.1 NEWS file, https://raw.githubusercontent.com/emacs-mirror/emacs/refs/he...

    ** Emacs is now capable of editing files with very long lines.
    The display of long lines has been optimized, and Emacs should no
    longer choke when a buffer on display contains long lines.  The
    variable 'long-line-threshold' controls whether and when these display
    optimizations are in effect.

    A companion variable 'large-hscroll-threshold' controls when another
    set of display optimizations are in effect, which are aimed
    specifically at speeding up display of long lines that are truncated
    on display.